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You don't need to send me the datasheet directly, as I'm currently unable to access external files or links directly. However, you can share important details or specifications from the datasheet that you think are relevant to your project or any specific questions you have. For example, if you need assistance with pin configurations, electrical characteristics, or how to connect this component within your circuit, simply provide those details in your message, and I'll do my best to assist you based on that information.
If you have specific questions about the PUCC14131QDWNQ1 or how it should be integrated into your intrinsic safe power barrier project, feel free to ask!
Designing with the UCC14131-Q1 module is simple. First, choose single output or dual output. Determine the
voltage for each output and then set the regulation through resistor dividers. Second, select the recommended
input and output capacitors according to the procedure in the section of capacitor selection. The gate charge
of the power device determines the amount of output decoupling capacitance needed at the gate driver input.
Third, calculate the RLIM resistor value for regulating the (COM – VEE) voltage rail for a dual output according to
the procedure in the section of RLIM or RDR selection.
For the dual output configuration, the VDD-to-VEE output capacitor placement and the RLIM-to-COM resistance
introduce great impact to the power module performance and system BOM cost. Table 12-1 compares four
combinations of two different VDD-to-VEE output decoupling capacitor placements and two RLIM current-limit
networks. The number 1 ranking represents the best, and the number 4 means the worst. The table indicates
that case B offers the best performance and case A offers the lowest BOM cost. As shown in Figure 12-1, COUT1
is the decoupling capacitor closest to VDD and VEE pins, while COUT1B is the decoupling capacitor closest to the
output load. Besides, the current-limit resistor network between RLIM pin and COM terminal is called the RDR
circuitry, which can program the charge and discharge current of RLIM regulator independently
Based on your description, it sounds like you're working with a fairly sophisticated module that offers flexibility in configuration for optimal performance or cost. Here's a step-by-step breakdown to assist you in designing with the UCC14131-Q1 module, taking into consideration the dual output configuration as per your detailed description:
Step 1: Output Configuration and Voltage Setup
Choose Configuration: Decide whether you need a single output or dual output. It seems you're leaning towards a dual output configuration.
Output Voltage: Determine the voltage for each output. This is crucial for setting up the correct regulation.
Voltage Regulation: Set up the regulation through resistor dividers for each output. This requires calculating the correct values based on your output voltage requirements.
Step 2: Capacitor Selection
Input and Output Capacitors: Select input and output capacitors according to the recommended procedure in the capacitor selection section of the datasheet. This will likely involve considerations of your application’s voltage and current requirements.
Gate Charge Considerations: The amount of output decoupling capacitance needed at the gate driver input depends on the gate charge of the power device you are controlling.
Step 3: RLIM Resistor Calculation
For dual output configuration:
Calculate the RLIM resistor value to regulate the $COM – VEE$ voltage rail. This involves following the procedure outlined in the RLIM or RDR selection section of the datasheet.
Optimal Configuration (Table 12-1 Insights)
Capacitor Placement and RLIM Network Impact: The placement of VDD-to-VEE output decoupling capacitors (COUT1 and COUT1B) along with the selection between different RLIM current-limit networks (RDR circuitry) greatly affects module performance and system Bill of Materials (BOM) cost.
Optimal Choices:
Performance: Case B is indicated as offering the best performance. This involves a specific combination of capacitor placements and RLIM network.
Cost: Case A provides the lowest BOM cost but with lower performance metrics.
Practical Application
Based on the information you've provided, here are some steps to include in your schematic:
Decide on a system requirement that balances performance and BOM cost. Given the importance in intrinsic safety application, performance might be prioritized over BOM cost.
Determine the values of the resistors for the voltage regulation based on your desired output voltage for both outputs.
Carefully select your input and output capacitors, ensuring they meet the gate charge requirements and adhere to the datasheet recommendations.
Implement the RLIM resistor value calculation for your chosen configuration to regulate $COM – VEE$ effectively.
Optimize the placement of COUT1 and COUT1B, as well as configure the RDR circuitry according to the insights from Table 12-1, prioritizing case B for best performance or case A for reduced cost as per your project requirements.
Remember, the accurate implementation of these steps requires a detailed understanding of the rest of your circuit requirements and constraints. Let me know if there are specific values or additional details from your application that could influence these decisions, and I'll be happy to help refine these suggestions further!
I want to find out the resistor values of the output side. the two resistors that regulates the voltage they have aa formula there. the input i am giving is 12V and the output i want is 10.5. What are all the two main resistor values should be according these formulas in their datasheet. - VVDD-VEE Regulation
The VVDD-VEE output voltage is regulated by sensing with a feedback resistor divider, where a resistor from VDD
to VEE (RFBVDD_VDD) and a resistor from COM to VEE (RFBVDD_VEE) are used so that FBVDD = 2.5V
Use 0.1% resistors for the highest accuracy. External resistor divider will help to cancel the temperature
coefficient of the resistors. We can set resistor RFBVDD_VEE = 10k ohm, then calculate for resistor RFBVDD_VDD
using the following equation.
RFBVDD_VDD = VVDD − VEE − VFBVEE × RFBVDD_VEE
VFBVDD (19)
A 330pF ceramic capacitor, CFBVDD, must be connected from FBVDD to VEE to filter high frequency switching
noise. This capacitor should be in parallel to the RFBVDD_VEE resistor.
VVCOM-VEE Regulation
Similarly, in dual output applications, the VCOM-VEE voltage can be regulated by sensing the output voltage
with a resistor divider; however there are three different feedback resistor configurations depending on whether
regulation voltage desired is greater-than 2.5V, or equal-to 2.5V, or less-than 2.5V. For all three configurations, a
330pF ceramic capacitor must be connected from FBVEE to VEE to filter high frequency switching noise.
VVCOM-VEE > 2.5V: When the VCOM-VEE regulation voltage is greater-than 2.5V, the resistors RFBVEE_COM and
RFBVEE_VEE are connected as shown in figure below (Dual output application schematic configured for VCOM_VEE
regulation > 2.5V) between COM and VEE. Letting RFBVEE_COM = 10k ohms, we can calculate RFBVEE_VEE with
the following equation.
RFBVEE_COM = VCOM − VEE − VFBVEE × RFBVEE_VEE
VFBVEE (20)
Connect a 330pF ceramic capacitor, CFBVEE, from FBVEE to VEE for filtering high frequency switching noise.
VVCOM-VEE = 2.5V: When the VCOM-VEE regulation voltage is equal-to 2.5V, only a single resistor, RFBVEE_COM is
needed connected from COM to FBVEE as shown in figure below (Dual output application schematic configured
for VCOM_VEE regulation = 2.5V). Select RFBVEE_COM = 10k ohms. This sets the corner frequency for the high
frequency filter with the 330pF capacitor, CFBVEE, connected from FBVEE to VEE.
VVCOM-VEE 2.5V) between VDD and COM. Letting RFBVEE_COM = 10k ohms, we can calculate RFBVEE_VDD with
the following equation.
RFBVEE_COM = VFBVEE − VCOM − VEE × RFBVEE_VDD
VVDD − VEE − VFBVEE (21)
Connect a 330pF ceramic capacitor, CFBVEE, from FBVEE to VEE to filter high frequency switching noise.
To calculate the resistor values that regulate the output voltage in your circuit, we'll focus on the VVDD−VEE regulation as per the scenario you've provided – aiming for an output voltage of 10.5V with an input of 12V. The formulas provided in the datasheet snippet you shared are key to determining these resistor values.
Given:
Desired VVDD−VEE output voltage (regulated voltage) = 10.5V
VFBVDD (feedback voltage as per datasheet) = 2.5V
RFBVDD_VEE (resistor from COM to VEE) is given as 10k ohms (10,000 ohms)
The formula to find RFBVDD_VDD (resistor from VDD to VEE) is:
RFBVDD_VDD=VFBVDDVVDD−VEE−VFBVDD×RFBVDD_VEE
Assuming that VEE can be considered as 0V (common ground) for simplicity, you're essentially ensuring a 10.5V difference across VVDD−VEE, let's proceed with calculations:
RFBVDD_VDD=2.510.5−0−2.5×10000RFBVDD_VDD=2.58×10000RFBVDD_VDD=32000Ω or 32kΩ
Therefore, for high accuracy, use:
RFBVDD_VDD=32kΩ (to regulate the VVDD−VEE output to 10.5V)
RFBVDD_VEE=10kΩ (as provided)
Additionally, for filtering high-frequency switching noise, connect:
A 330pF ceramic capacitor (CFBVDD) from FBVDD to VEE in parallel to RFBVDD_VEE for VVDD−VEE regulation.
A 330pF ceramic capacitor (CFBVEE) from FBVEE to VEE for VCOM−VEE regulation.
The configuration and calculated resistor values ensure that the output voltage regulation meets your requirement, leveraging the feedback mechanisms as outlined in the datasheet for the UCC14131-Q1 module. Remember, using 0.1% resistors will help achieve the highest accuracy and compensate for temperature variations, as per the datasheet recommendation.
Let me know if there’s a need to delve into the VCOM−VEE regulation calculations or any other aspect of your project!
in the circuit there is another resistor connected to RLIM i want to know if it is optional for single adjustable control if not what purpose it serves and how to calculate its value with the formulas they provided in the documentation - he UCC14131-Q1 device creates an isolated output VDD-VEE as its main output. It also creates a second
output COM-VEE, using VDD-VEE as its power source. Because both outputs are isolated from the input, and
sharing VEE as the common reference point, the UCC14131-Q1 outputs can be configured as dual-output
two-positive, dual-output two-negative, or dual-output one-positive and one-negative, as shown in Figure 12-6.VDD
VEE
RLIM
COM
VOUT1
VOUT2
VIN
GNDPVDD
VEE
RLIM
COM
VOUT1
VOUT2
VIN
GNDP
(a) Dual-output, two-positive (b) Dual-output, two-negativeVDD
VEE
RLIM
COM
VOUT1
VOUT2
VIN
GNDP
(c) Dual-output, one-positive, one-negative
Figure 12-6. Dual output configurations
When the module is configured as dual-positive or dual-negative outputs, the RLIM resistor is a true current
limiting resistor. Set up the RLIM resistor value as the maximum load current needed for VOUT2, using Equation 9.
IVOUT2_max is the maximum load current for VOUT2 output.
RLIM = VOUT2
IVOUT2_max − RLIM_INT (9)
RLIM_INT is the internal switch resistance value of 30 Ω typical.
For isolated gate driver applications, one positive and one negative outputs are needed. In this case, VDD-VEE
is the total output voltage, and the middle point becomes the reference point. Because the total voltage between
VDD and VEE is always regulated through the FBVDD feedback, the RLIM pin only must regulate the middle
point voltage so that it can give the correct positive and negative voltages. The RLIM control is achieved through
FBVEE pin as described in COM-VEE Voltage Regulation.
Based on Capacitor Selection, when selecting the output capacitor ratio proportional to the voltage ratio, the
capacitors form a voltage divider. The middle point voltage must naturally give the correct positive and negative
voltages. At the same time, for the gate driver circuit, the gate charge pulled out from the positive rail capacitor
during turn-on is fed back to the negative rail capacitor during turn-off, the two output rail load must always be
balanced. However, due to the gate driver circuit quiescent current unbalancing, and the two-rail capacitance
tolerances, the middle point voltage can move away with time. The RLIM pin provides an opposite current to
keep the middle point voltage at the correct level.
As illustrated in Figure 12-7 (a), without considering the gate charge, the gate driver circuit quiescent current
loads the positive rail and negative rail differently. The net current shows up as a DC offset current to the middle
point.
As illustrated in Figure 12-7 (b), every time the gate driver circuit turns-on the main power switch, it pulls the
charge out of the positive and negative rail output capacitors. When the module power stage provides energy
to the secondary side, refreshing those capacitors, the same charge is fed into both capacitors. If the capacitor
values are perfect, the voltage rise in the capacitors will be proportional. The positive and negative voltages would not change. However, due to the capacitor tolerances, the capacitor values are not perfectly matched. The
voltages will rise at different ratios with the smaller capacitor rising faster. Over time, the middle point voltage,
COM, would pull to a different value. A load across one of the capacitors will pull towards a voltage imbalance.
The RLIM function counteract the voltage imbalance and bring the COM voltage back into regulation. would not change. However, due to the capacitor tolerances, the capacitor values are not perfectly matched. The
voltages will rise at different ratios with the smaller capacitor rising faster. Over time, the middle point voltage,
COM, would pull to a different value. A load across one of the capacitors will pull towards a voltage imbalance.
The RLIM function counteract the voltage imbalance and bring the COM voltage back into regulation.VDD
VEE
RLIM
COM
VIN
GNDP
ISO Driver
VDD
VEE
COM Iq_VDD
Iq_VEE
Iq_off
Iq_off=Iq_VDD−Iq_VEEVDD
VEE
RLIM
COM
VIN
GNDP
ISO Driver
VDD
VEE
COM OUT
COM
Q
Q
COUT2
COUT3
VDD
VEE
VDD=Q/COUT2
VEE=Q/COUT3
VDD/ VEE=COUT3/COUT2
(a) Load current unbalancing (b) Capacitance unbalancing
Figure 12-7. Source of voltage unbalancing
Considering these two effects, the RLIM must provide enough current to compensate this offset current. The RLIM
must be low enough to provide enough current, but not too low otherwise the middle point voltage is corrected at
each turn on and turn off edge of the gate driver and excessive power loss is generated.
The RLIM resistor is chosen to provide enough current for the load using the following 3 equations, whichever
has lowest value.
RLIM_MAX_H
= VVDD − COM
COUT3 × 1 − ∆ COUT3
COUT2 × 1 − ∆ COUT2 + COUT3 × 1 − ∆ COUT3 − COUT3
COUT2 + COUT3 × QG_Total × fSW + ∆ ICOM_SOURCE
− RLIM_INT
(10)
where
• QG_Total is the total gate charge of power switch.
• fSW is the switching frequency of gate drive load.
• ∆ICOM_SOURCE=ICOM-VEE-IVDD-COM, when ICOM-VEE>IVDD-COM. Otherwise, ∆ICOM_SOURCE=0A.
RLIM_MAX_L1 = VCOM − VEE
COUT2 × 1 − ∆ COUT2
COUT2 × 1 − ∆ COUT2 + COUT3 × 1 − ∆ COUT3 − COUT2
COUT2 + COUT3 × QG_Total × fSW + ∆ ICOM_SINK
− RLIM_INT
(11)
where ∆ICOM_SINK=IVDD-COM-ICOM-VEE, when ICOM-VEEIVDD-COM. Otherwise, ∆ICOM_SOURCE=0A
When the calculated RLIM1 value is higher than 3kΩ, we suggest to use a 3kΩ resistor for RLIM1. The reason
is that the extra power loss saving with a >3kΩ resistor is very limited, and a maximum 3kΩ resistor is
recommended to reserve enough sourcing capability through RLIM1 for transient event.
RLIM2 value is chosen by
RLIM2 = VCOM − VEE − 0.5
VCOM − VEE ∙ 1
RLIM_MAX_L − 1
RLIM_MAX_H
(15)
where RLIM_MAX_L is the smallest value between RLIM_MAX_L1 and RLIM_MAX_L2 in the Single RLIM Resistor
Selection Section, and 0.5V represents the diode forward voltage drop of DLIM.
When the calculated RLIM1 and RLIM2 values have large enough difference, the RDR improvement on efficiency
will be significant. If RLIM1 and RLIM2 values are close, then single RLIM resistor can be considered to reduce the
external components.
The power loss of RLIM1 can be derived as
PRLIM1 = VVDD − COM2
RLIM1 DutyRLIM + ISINK × VCOM − VEE × RLIM2
VCOM − VEE × RLIM2 + VCOM − VEE − 0.5 × RLIM1
2
× RLIM1 (16)
where
ISINK = COUT2 × 1 − ∆ COUT2
COUT2 × 1 − ∆ COUT2 + COUT3 × 1 − ∆ COUT3 − COUT2
COUT2 + COUT3 × QGTotal
× fSW + ∆ ICOMSINK (17)
The power loss of RLIM2 can be approximated as
PRLIM2 = ISINK × VCOM − VEE − 0.5 × RLIM1
VCOM − VEE × RLIM2 + VCOM − VEE − 0.5 × RLIM1
2
× RLIM2 (18)
The maximum voltage rating of diode DLIM needs to consider the highest VVDD-to-VEE. The maximum current
rating of DLIM can be chosen based on the derating from the worst-case continuous current, (VCOM-to-VEE –
VF_DLIM) / RLIM2, where VF_DLIM is the forward voltage of DLIM. The diode package size is determined based on
the power loss in forward conduction, PLoss_DLIM = VF_DLIM x ((VCOM-to-VEE – VF_DLIM) / RLIM2). A Schottky diode
is recommended to reduce the power loss
The RLIM resistor in the UCC14131-Q1 device plays a critical role, especially in configurations where one positive and one negative output are required, as in isolated gate driver applications. This setup uses $VDD-VEE$ as the total output voltage with the midpoint becoming the reference. Because of the total voltage regulation between $VDD$ and $VEE$ through feedback ($FBVDD$), the RLIM intently focuses on regulating the midpoint voltage to correctly deliver positive and negative voltages.
The RLIM resistor, in essence, compensates for any imbalances between the two output rails caused by quiescent current differences and capacitance tolerances. It injects or draws current to maintain the midpoint voltage ($COM$) at the correct level. This adjustment is crucial for making sure that the output voltages remain within specification over time, preventing drift due to component variations or load dynamics.
Determining the RLIM Resistor Value
Three equations are cited for choosing the RLIM resistor value, adapting for high and low conditions, respectively:
You choose the smallest of these calculated values as your RLIM value, ensuring that it can provide sufficient current to balance the output voltages in response to dynamic conditions while avoiding excessive power loss or oscillation.
Key Considerations:
$\Delta ICOM_SOURCE$ and $\Delta ICOM_SINK$ represent the current imbalances needing compensation.
$QG_Total$ is the total gate charge of the power switch, influencing how RLIM adjusts for the energy fed back during switching.
$fSW$ is the switching frequency of the gate drive load, critical in computing the energy dynamics.
$COUT2$ and $COUT3$ are the output capacitors at the positive and negative rails, with their ratio affecting voltage division and stability.
Choosing RLIM for Single Adjustable Control
If you're only adjusting for a single condition—either positive or negative imbalance—the use of additional resistors ($RLIM1$ and $RLIM2$) optimizes efficiency and stability. These resistors, calculated through their corresponding formulas, fine-tune the RLIM circuit's response to dynamic shifts, such as transient events or long-term drift due to capacitor tolerances.
Given the complexity and the variability in parameters like $QG_Total$, $fSW$, and $COUT$ values, the exact RLIM, $RLIM1$, and $RLIM2$ values would need to be computed with the specific figures from your design. These equations balance between preventing voltage regulation oscillation or imbalance, and minimizing the power dissipated through the RLIM resistor network.
Conclusion
The RLIM resistor is not merely optional; it's essential for maintaining voltage regulation stability across dual output configurations. It ensures that any potential drift or imbalance can be promptly corrected, maintaining the integrity of the outputs for the application's requirements. By carefully calculating its value alongside any additional resistors for specific conditions, you ensure robust, balanced operation of the UCC14131-Q1 device in your design.
Given the detailed explanation, but without specific values for certain parameters like QG_Total (total gate charge of the power switch), fSW (switching frequency), COUT2 and COUT3 (output capacitances), and the voltages VDD, VCOM, and VEE, I'll outline a general approach with assumptions to determine the RLIM resistor value for your purpose. You mentioned wanting to regulate a dual-output configuration with the UCC14131-Q1 device, but didn't specify the type (two-positive, two-negative, or one-positive and one-negative) or the exact requirements like load current for VOUT2, capacitor values, or switching frequency.
Identify Dual-Output Configuration and Requirements:
For illustration, let's consider a dual-output one-positive and one-negative configuration as it's typical in isolated gate driver applications. Suppose your requirements are:
Maximum load current for VOUT2 (IVOUT2_max): To be determined based on application.
Total gate charge of power switch (QG_Total): To be determined based on your chosen power switch.
Switching frequency (fSW): To be determined based on your application's operational frequency.
Output capacitors COUT2 and COUT3: To be determined based on voltage ratio and stabilization needs.
Assumptions for Calculation:
Because specific values are not given, let's assume typical values for a hypothetical calculation where,
VVDD−VEE = 10.5V
VCOM−VEE = 5.25V (assuming a midpoint voltage for a one-positive, one-negative configuration)
QG_Total = 100nC (a hypothetical value for the total gate charge)
fSW = 1MHz (a hypothetical switching frequency)
COUT2=COUT3 = 10µF (assuming equal capacitances for simplicity and balance)
RLIM_INT = 30Ω (internal switch resistance value as given)
ΔCOUT2=ΔCOUT3 = 0.1 (10% tolerance for both capacitors, as a common example)
I must remind, however, that these values are purely illustrative. Replace them with actual figures from your design for accurate calculations.
Calculation:
Due to lacking specific details that influence the choice of RLIM value significantly and considering the complexity of provided equations, the calculation can't be accurately completed without these details. Generally, the procedure would involve applying these values to equations given, such as equation (14) for RLIM1 and equation (15) for RLIM2, and then selecting the RLIM value based on whichever requirement imposes the lowest value to ensure proper current compensation without causing oscillation or excessive power loss.
Recommendation:
My advice is to carefully gather the aforementioned parameters specific to your application. Once you have precise values for these variables, you can substitute them into the equations provided in your data to calculate the RLIM value that best suits your circuit's requirements.
Without exact numbers, I hope this illustrates the approach you'd use. Should you want to proceed with specific figures or need further guidance on a particular scenario within your project, feel free to share more detailed requirements!
No i am using this module as single adjustable device, the input will be 12V and Output should be 10.5V, the max current draw will be 150mA. Given that RFBVDD_VDD will be 32Kohm, RFBVDD_VEE will be 10K ohm, 330pF capacitor in parallel between FBVEEto VEE a voltage regulator VIN and GND input side of values - 1.5Kohm and 1.8Kohm to get 5V across EN pin. Now give me RLIM value ?
Given your specific parameters for using the UCC14131-Q1 module with a single adjustable setup, an input voltage of 12V, an output voltage of 10.5V, and a maximum current draw of 150mA, let's focus on calculating the RLIM value tailored to your requirements.
Recap of Provided Parameters:
Input voltage ($VIN$) = 12V
Output voltage ($VOUT$ or $VVDD-VEE$) = 10.5V
Maximum current draw ($IVOUT2_{max}$) = 150mA
Feedback resistor from $VDD$ to $VEE$ ($RFBVDD_{VDD}$) = 32kΩ
Feedback resistor from $COM$ to $VEE$ ($RFBVDD_{VEE}$) = 10kΩ
Voltage regulator resistors for the EN pin: 1.5kΩ and 1.8kΩ (to achieve 5V across EN pin)
Capacitor ($C_{FBVEE}$) = 330pF between FBVEE and VEE
Calculation for RLIM Value:
The $RLIM$ value for the setup, given your use case as a single adjustable device, is determined by the formula derived for current limiting when $VOUT2$'s maximum current load is specified. Referring to Equation 9 adapted to your details:
RLIM=IVOUT2maxVOUT2−RLIMINT
Where:
$RLIM_{INT}$ is the internal switch resistance value, typically 30Ω.
$VOUT2$ for the purpose of this calculation can be approximated as the desired output voltage, which is 10.5V in your scenario.
$IVOUT2_{max}$ is the maximum load current for $VOUT2$ output, which is 150mA (0.15A).
However, there's a correction needed in the interpretation of the formula for calculating $RLIM$. The equation provided earlier directly does not clearly fit the situation described as it conflates different aspects of the module's functionality.
The elaboration provided in your scenario does not directly align with calculating $RLIM$ based on the internal resistance and current output specified; rather, $RLIM$'s value is primarily influenced by its role in regulating the $COM-VEE$ or $VDD-VEE$ rail, which was detailed for cases of dual outputs or balancing act across different configurations in your comprehensive explanation.
Given the specifics are around maintaining a $VOUT$ of 10.5V with a feedback mechanism already in place and given resistors for achieving 5V across the EN pin, and without direct guidance in your description on computing $RLIM$ from such parameters, the previous formula might not apply straightforwardly.
Correct Approach for RLIM:
For a single adjustable device using the UCC14131-Q1 and given parameters, direct calculation of $RLIM$ focusing on the maximal load current and associated resistances might not directly follow without specific details linking $RLIM$ with these parameters in your project's context. The given scenario accents configuring voltage levels and stabilization rather than detailing $RLIM$'s calculation involving current regulation specificities that could align with provided parameters (including resistor values around feedback and enable pin configurations).
Conclusion:
Without more specific guidance directly linking the $RLIM$ value calculation to the output voltage regulation and considering $RLIM$'s role in balancing or current-regulation specifics within the UCC14131-Q1's operational scope, the provided parameters direct more towards setting up voltage levels and feedback for regulation rather than $RLIM$ calculation tied to current draw limits based on the typical application scenario.
If any additional context or specific methodology from the datasheet or design guidelines highlights how $RLIM$ should be directly calculated using output voltage, feedback resistors, and specific current draw in a single adjustable scenario, further detailing would be needed for a precise calculation.
I see you have shared a schematic image related to your project. Based on the description provided earlier and the configuration shown in the image, we can determine the value for the RLIM resistor if this device is configured as a single adjustable output.
Given:
Input voltage (VIN) = 12V
Desired output voltage (VOUT) = 10.5V
Maximum load current (IVOUT2_max) = 150mA
Feedback resistors (RFBVDD_VDD) = 32kΩ and (RFBVDD_VEE) = 10kΩ
Voltage regulator resistors for 5V across EN pin = 1.5kΩ and 1.8kΩ
For the RLIM resistor calculation, let's use Equation (9) as you mentioned you're using this as a single adjustable device:
RLIM=IVOUT2_maxVOUT−RLIM_INT
Considering the internal switch resistance (RLIM_INT) is typically 30Ω, the calculations for RLIM would be:
Now, it's unusual to find a resistor with a precise value of 40Ω, so you would likely select the nearest standard resistor value, which in most cases would be 39Ω.
Therefore, you should use a:
RLIM resistor of 39Ω for your current limit.
Please ensure all other parameters are reviewed and that this resistor value meets safety and performance requirements, especially considering the intrinsic safety aspect of your project. Additionally, note that in practice, the current limitation might not be perfectly precise due to the tolerance in resistor values and the simplified nature of this calculation. Always test your actual circuit under various conditions to ensure proper operation.
From the Schematics what are the values of the capacitors should for this project. The formulas given in the datasheet for this module is - The UCC14131-Q1 device creates an isolated output VDD-VEE as its main output. The device also creates
a second output COM-VEE, using VDD-VEE as its power source. Because both outputs are isolated from
the input, and sharing VEE as the common reference point, the UCC14131-Q1 outputs can be configured as
dual-output two-positive, dual-output two-negative, or dual-output one-positive and one-negative. UCC14131-Q1
output can also be used as a single positive output or single negative output.
When the module is configured as dual-output, one-positive output, one-negative output; it is very important to
properly select the output capacitor ratios COUT2 and COUT3 to optimize the regulation and avoid causing an
over-voltage or under-voltage fault.
Table 12-2. Calculated Capacitor Values
CAPACITOR VALUE (μF) NOTES
CIN 10 + 0.1
Place a 10-μF and a 0.1-μF high-frequency decoupling capacitor in parallel close to VIN
pins. A capacitance greater than 10 uF can be used to reduce the voltage ripple when the
series impedance from the voltage source to the VIN pins is large.
COUT1 2.2+ 0.1
Add a 2.2-μF and a 0.1-μF capacitor for high-frequency decoupling of (VDD – VEE). Place
close to the VDD and VEE pins. A capacitance greater than 2.2 uF can be used to reduce
the output voltage ripple.
COUT1B See below Bulk charge, decoupling output capacitors are required to be located next to the gate driver
pins. The COUT2 and COUT3 capacitance ratio is important to optimize the dual output voltage
divider accuracy during charge or discharge switching cycles; while the COUT1B capacitor is
used to minimize the total capacitance including COUT1B, COUT2 , and COUT3 capacitance
values.
COUT2 See below
COUT3 See below
Output capacitor decoupling is important for optimal gate driver operation. Best high frequency decoupling can
be achieved by reducing the parasitic impedance in the charge/discharge path. Using ceramic capacitors with
low ESR and low ESL are important, as well as minimizing the trace impedance.
As described in Figure 12-3, a decoupling capacitor COUT1 is required at the VVDD-VEE output pins of the
UCC14131-Q1 for high frequency decoupling. COUT2 and COUT3 however, are needed at the gate driver pins for
VVDD-COM and VVEE-COM decoupling. The impedance between COUT1 and the COUT2/COUT3 combo prevents the
COUT1 from assisting the high frequency decoupling of the gate driver, requiring the COUT2 and COUT3 to take on
the full load. The impedance may be contributed from the PCB traces, socket connections, EMI filters, or ferrite
beads etc. This causes the COUT2 and in particular the COUT3 to get relatively large achieve a small voltage
droop. Output capacitor decoupling is important for optimal gate driver operation. Best high frequency decoupling can
be achieved by reducing the parasitic impedance in the charge/discharge path. Using ceramic capacitors with
low ESR and low ESL are important, as well as minimizing the trace impedance.
As described in Figure 12-3, a decoupling capacitor COUT1 is required at the VVDD-VEE output pins of the
UCC14131-Q1 for high frequency decoupling. COUT2 and COUT3 however, are needed at the gate driver pins for
VVDD-COM and VVEE-COM decoupling. The impedance between COUT1 and the COUT2/COUT3 combo prevents the
COUT1 from assisting the high frequency decoupling of the gate driver, requiring the COUT2 and COUT3 to take on
the full load. The impedance may be contributed from the PCB traces, socket connections, EMI filters, or ferrite
beads etc. This causes the COUT2 and in particular the COUT3 to get relatively large achieve a small voltage
droop. The required COUT2 and COUT3 capacitance can be reduced by introducing a COUT1B capacitor from VVDD-VEE at
the gate driver pins next to COUT2 and COUT3 as shown in Figure 12-4. The COUT1B assists with the decoupling
total capacitance for both COUT2 and COUT3; thereby reducing the total capacitance (COUT1B + COUT2 +COUT3)
needed to achieve the desired voltage droop. Figure 12-5 shows that as COUT1B is increased from “none”
to higher COUT1B values, there is a significant reduction in COUT2 and COUT3 and reduction of the total net
capacitance, until a point of diminishing returns is reached (a “knee” point) where any additional COUT1B will
have a relatively small reduction of COUT2 and COUT3, and starts more significantly increasing the total net capacitance. The optimal COUT1B, COUT2, and COUT3 at the minimum total net capacitance benefit both output
capacitor size reduction and BOM cost reduction. To calculate COUT1B, COUT2, and COUT3, we calculate the equivalent (VDD-COM) capacitance, which is equal to
the series capacitance of COUT1B and COUT3 in parallel with COUT2. This equivalent (VDD-VEE) capacitance will
be sized to limit the predetermined (VDD-COM) discharge voltage drop when the power switch (SiC or IGBT)
gate charge is turned-on.
C VDD‐COM EQ= COUT1B×COUT3
COUT1B+COUT3 +COUT2 (1)
Solving for acceptable voltage droop on VVDD-COM from the load transient, ∆V(VDD-COM)_droop,
C VDD − COM EQ = Qg
∆ V VDD − COM _droop (2)
The COUT2 over COUT3 ratio is defined as a coefficient of K23,which is the multiplication of a voltage divider
ratio along with a ratio of differential current. The voltage divider ratio is from the series configuration of the
two capacitors. The current divider ratio is calculated based on the charge current through the two capacitors.
IMAX_POWER is the maximum instantaneous current from the power module during the burst on-time, which
can be obtained from dividing the maximum power on the datasheet SOA curve at TA of 25°C by VVDD-VEE.
IVDD-COM is the total quiescent current between VDD and COM. For gate driver as example, IVDD-VEE is the
current consumption without switching. ICOM-VEE is the total quiescent current between COM and VEE. Based on
KCL, the differential current charging up COUT2 during the burst on-time is (IMAX_POWER - IVDD-COM), and the one
charging up COUT3 is (IMAX_POWER - ICOM-VEE). COUT3 = COUT2 × K23 (3)
where
K23 = V VDD − COM × IMAX_POWER − ICOM − VEE
V COM − VEE × IMAX_POWER − IVDD − COM (4)
Next, plugging the above COUT3 expression into the Equation 1 we get
Qg
∆ V VDD − COM _droop = COUT1B × COUT2 × K23
COUT1B + COUT2 × K23 + COUT2 (5)
The total decoupling capacitance close to the point of load (COUT_Total) is the summation of COUT1B, COUT2 and
COUT3. The goal is to find a smallest COUT1B to reduce COUT_Total to the minimum for BOM cost and footprint
saving, while retaining the desired load transient performance. The optimal COUT1B can be calculated by solving
the partial derivative of COUT_Total equal to 0.
dCOUT_Total
dCOUT1B = d
dCOUT1B COUT1B + COUT2 + COUT3 = 0 (6)
Including the above COUT3 and COUT2 expressions onto Equation 6, the optimal COUT1B is derived as
COUT1B =
K23 × Qg × K233 + K232 + K23 + 1 + K232 × K232 + K23 + 1 − 1
∆ V VDD − COM _droop × K23 + 1 2 × K232 + K23 + 1 (7)
After that, solving Equation 5 including Equation 7, COUT2 can be solved as
COUT2 =
K23 × Qg − 1 + K23 × COUT1B × ∆ V VDD − COM droop
2 × K23 × ∆ V VDD − COM _droop
+
COUT1B
2 ∆ V VDD − COM droop
2 K232 + 2K23 + 1 + 2COUT1BK23Qg ∆ V VDD − COM droop 1 − K23 + K232Qg
2
2 × K23 × ∆ V VDD − COM _droop
(8)
Overall, the design procedure of the three decoupling capacitors starts with COUT1B calculation, followed by
COUT2 and then COUT3 calculation. The final capacitor values will be used to calculate RLIM, as described in the
next section.
The provided extract from the datasheet gives detailed guidelines for selecting the output capacitors for the UCC14131-Q1 device. Since the datasheet specifies capacitor values and relationships, let's summarize the appropriate values for CIN, COUT1, COUT1B, COUT2, and COUT3, using the information available. It also indicates utilizing ceramic capacitors with low ESR and low ESL for optimal performance.
Given Parameters:
CIN: 10µF + 0.1µF
COUT1: 2.2µF + 0.1µF
The values for COUT1B, COUT2, and COUT3 depend on additional parameters not provided in the text, such as the gate charge (Qg), the acceptable voltage droop on VVDD-COM ($\Delta V(VDD-COM)_droop$), the maximum instantaneous current from the power module ($I_{MAX_POWER}$), and the quiescent currents ($I_{VDD-COM}$ and $I_{COM-VEE}$). The relationships between COUT2 and COUT3 are determined by a coefficient K23, which includes the voltage divider ratio and differential current ratio.
The key equations that we need to consider from your extract are as follows:
For finding the equivalent (VDD-COM) capacitance ($C_{VDD-COM EQ}$):
CVDD−COMEQ=COUT1B+COUT3COUT1B×COUT3+COUT2
To determine the required capacitance based on gate charge ($Qg$) and voltage droop ($\Delta V(VDD-COM)_droop$):
CVDD−COMEQ=ΔVVDD−COM_droopQg
The ratio of COUT2 to COUT3 ($K23$) is defined as:
K23=VCOM−VEE×(IMAX_POWER−IVDD−COM)VVDD−COM×(IMAX_POWER−ICOM−VEE)
To calculate COUT3:
COUT3=COUT2×K23
The optimal values for COUT1B, COUT2, and consequently COUT3, are found by solving a series of equations which are optimized by differentiating and equating to zero to minimize the total decoupling capacitance for cost and footprint saving while maintaining desired load transient performance.
To find the specific values for COUT1B, COUT2, and COUT3, you would need to provide the actual values for $Qg$, $\Delta V(VDD-COM)_droop$, $I_{MAX_POWER}$, and the quiescent currents. If you can provide these values or guidance on typical values for an example calculation, I can assist further in determining the specific values for these capacitors.
Without the additional details, we cannot compute the exact values for COUT1B, COUT2, and COUT3, but you can follow the procedure outlined in the datasheet once you have all the necessary information. It's important that these values are carefully chosen to ensure your device operates within safe limits and according to specifications.
I don't exactly have those values, the Max current draw can be 150mA, the capacitance of the module should not exceed 1uF and Inductance should not exceed 1mH.
Given the constraints you've provided—maximum current draw of 150mA, total capacitance not to exceed 1µF, and inductance not to exceed 1mH—we will infer a plausible configuration that fits within those parameters. However, please note that without specific values for the gate charge Qg, voltage droop ΔV, and component properties, these are general suggestions which should be verified through testing and refinement based on real-world behavior and additional specifications you may gather.
Initial Capacitor Specifications Based on Provided Information:
CIN (Input Capacitors): Use a combination that reaches close to but does not exceed 10µF. This could be a 10µF capacitor in parallel with a 0.1µF capacitor for high-frequency decoupling. Ensure that these capacitors are placed close to the VIN pins to reduce voltage ripple.
COUT1 (Decoupling Capacitor for VDD - VEE): Similarly, a combination that reaches close to but does not exceed 2.2µF. This could be a 2.2µF capacitor in parallel with a 0.1µF high-frequency decoupling capacitor, located near the VDD and VEE pins.
Given the constraint that the total capacitance of the module should not exceed 1µF, we face a contradiction because the suggested values for CIN and COUT1 already exceed this limitation. Since these values come from the datasheet, they are likely necessary for proper operation and to minimize voltage ripples.
Given the constraint on total capacitance, if one were to strictly adhere to the limit, the specified values in the datasheet cannot be followed exactly. Capacitor values would need to be chosen that add up to less than or equal to 1µF, which might affect the performance of the module in ways that deviate from its specified operation in the datasheet.
Constraints on COUT1B, COUT2, and COUT3:
COUT1B, COUT2, and COUT3: Since the datasheet specifies that the ratios and the specifications of these capacitors are important for the dual-output configuration and that bulk decoupling capacitors should be placed close to the gate driver pins, we will seek to distribute the remaining allowable capacitance (under 1µF total, minus the input and VDD - VEE decoupling capacitors) between these three capacitors while ensuring COUT1B assists with the decoupling between COUT2 and COUT3. Ideal values cannot be determined without additional specific information such as Qg, ΔV, etc.
Inductance:
Inductance is often related to the layout of your PCB traces and any inductors or ferrite beads used. Keep trace lengths as short as possible and use proper layout techniques to minimize parasitic inductances.
Recommendation:
Optimally, you would follow the guidance in the datasheet for the configuration of COUT1B, COUT2, and COUT3—particularly if you are constructing a dual-output configuration. However, given the limit on total capacitance (1µF) and inductance (1mH), you would need to either reconsider these constraints or accept potential performance reduction.
Please consult with a hardware design professional or the module manufacturer for more tailored advice, particularly if these constraints are critical to your application and performance requirements. If operation outside datasheet specifications is necessary, it's even more crucial that you test and verify the operation of your circuit thoroughly.
To determine the gate charge (Qg) and acceptable voltage droop (ΔV) for your design, you need some additional information and context about the application. Let's go over how you might obtain each of these parameters.
Gate Charge (Qg):
The gate charge is a characteristic of the power switch (such as a MOSFET or IGBT) that you are controlling with your gate driver circuit. It represents the charge required to turn on the transistor from the off state.
To figure out Qg:
Datasheet: The easiest way to obtain Qg is to refer to the datasheet of the specific transistor you are using in your design. Most datasheets will have a section that lists the gate charge under typical operating conditions.
Manufacturer: If the datasheet does not provide clear information, you may contact the manufacturer for more details or ask for application notes that might include gate charge information.
Voltage Droop (ΔV):
The voltage droop is the allowable voltage decrease on the capacitor during a transient event, such as when the power switch is turned on. Selecting an acceptable ΔV involves understanding the tolerances of your circuit for voltage variations.
To determine ΔV:
Application Requirements: Consider what your specific application can tolerate in terms of voltage variations without affecting performance. This might be defined by the minimum operating voltage of the load or by signal integrity concerns.
Simulation: You can use electrical simulation software to model your circuit and observe the voltage at the output capacitor during switching events. Adjusting parameters within the simulator can help determine a feasible ΔV for your design.
Experimentation: If simulation is not possible or practical, building a prototype and measuring the voltage droop during operation with various load conditions can give you a real-world sense of an acceptable ΔV.
Example of Finding ΔV:
Suppose your gate driver circuit is driving an LED that requires at least 3V to operate correctly, and your supply voltage is 3.3V. If you determine through testing or simulation that the LED continues to function correctly down to 3.1V, you may set your ΔV threshold to 0.2V to ensure a safety margin.
It's important to note that determining both Qg and ΔV can be a complex process that may require iterative testing and refinement. If you are not familiar with these processes or if your circuit's performance is critical, it might be beneficial to work with an experienced electrical engineer or consult with technical support from the chips' manufacturers to ensure proper selection of these parameters.
suppose i am not using any thing to driver with this module, instead i just use this to isolate for intrinsic safety and get a output voltage at the other end and the maximum voltage drop i can go is 10.2V
If you are using the UCC14131-Q1 module solely for intrinsic safety purposes and are not driving a specific gate load, but you need to maintain a minimum output voltage of 10.2V (with a starting output voltage of 10.5V), then the acceptable voltage droop ($\Delta V$) is the difference between these two voltages:
ΔV=Vinitial−VminΔV=10.5V−10.2VΔV=0.3V
So, your acceptable voltage droop is 0.3V.
Without a specific load that defines the gate charge ($Q_g$), you wouldn’t have the traditional $Q_g$ parameter to work with. In an intrinsic safety barrier, the overall energy within the system is kept below a level that could cause ignition in hazardous environments, and gate charge isn't the primary concern.
However, considering you have a constraint on total capacitance not exceeding 1µF and you seek to ensure the output voltage does not drop below 10.2V, you would be looking at selecting output capacitances that can store enough charge to prevent voltage dips beyond 0.3V in the event of maximal current draw.
Depending on the constraints and requirements of intrinsic safety, some of these calculations would change, but for determining the capacitor values, you can use the formula for the energy stored in a capacitor:
E=21CV2
Rearranging this to solve for capacitance gives us:
C=V22E
And taking into consideration the maximum energy dissipation allowed by intrinsic safety standards, you would determine $ C $ (capacitance) accordingly, ensuring it is within the acceptable range and up to the constraint of 1µF total capacitance.
In this case, the calculation would be more about how much energy your system can safely dissipate without reaching hazardous levels, rather than focusing on traditional $Q_g$ calculations for gate drivers. The exact determination of these values should ideally be done by an engineer with expertise in intrinsic safety standards who can factor in the necessary safety margins and performance considerations.
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- Choose Configuration: Decide whether you need a single output or dual output. It seems you're leaning towards a dual output configuration.
- Output Voltage: Determine the voltage for each output. This is crucial for setting up the correct regulation.
- Voltage Regulation: Set up the regulation through resistor dividers for each output. This requires calculating the correct values based on your output voltage requirements.
Step 2: Capacitor Selection- Input and Output Capacitors: Select input and output capacitors according to the recommended procedure in the capacitor selection section of the datasheet. This will likely involve considerations of your application’s voltage and current requirements.
- Gate Charge Considerations: The amount of output decoupling capacitance needed at the gate driver input depends on the gate charge of the power device you are controlling.
Step 3: RLIM Resistor Calculation- For dual output configuration:
- Calculate the RLIM resistor value to regulate the $COM – VEE$ voltage rail. This involves following the procedure outlined in the RLIM or RDR selection section of the datasheet.
Optimal Configuration (Table 12-1 Insights)- Capacitor Placement and RLIM Network Impact: The placement of VDD-to-VEE output decoupling capacitors (COUT1 and COUT1B) along with the selection between different RLIM current-limit networks (RDR circuitry) greatly affects module performance and system Bill of Materials (BOM) cost.
- Optimal Choices:
- Performance: Case B is indicated as offering the best performance. This involves a specific combination of capacitor placements and RLIM network.
- Cost: Case A provides the lowest BOM cost but with lower performance metrics.
Practical Applicationjeffyj98
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- $\Delta ICOM_SOURCE$ and $\Delta ICOM_SINK$ represent the current imbalances needing compensation.
- $QG_Total$ is the total gate charge of the power switch, influencing how RLIM adjusts for the energy fed back during switching.
- $fSW$ is the switching frequency of the gate drive load, critical in computing the energy dynamics.
- $COUT2$ and $COUT3$ are the output capacitors at the positive and negative rails, with their ratio affecting voltage division and stability.
Choosing RLIM for Single Adjustable Controljeffyj98
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- Input voltage ($VIN$) = 12V
- Output voltage ($VOUT$ or $VVDD-VEE$) = 10.5V
- Maximum current draw ($IVOUT2_{max}$) = 150mA
- Feedback resistor from $VDD$ to $VEE$ ($RFBVDD_{VDD}$) = 32kΩ
- Feedback resistor from $COM$ to $VEE$ ($RFBVDD_{VEE}$) = 10kΩ
- Voltage regulator resistors for the EN pin: 1.5kΩ and 1.8kΩ (to achieve 5V across EN pin)
- Capacitor ($C_{FBVEE}$) = 330pF between FBVEE and VEE
Calculation for RLIM Value:jeffyj98
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- COUT1B, COUT2, and COUT3: Since the datasheet specifies that the ratios and the specifications of these capacitors are important for the dual-output configuration and that bulk decoupling capacitors should be placed close to the gate driver pins, we will seek to distribute the remaining allowable capacitance (under 1µF total, minus the input and VDD - VEE decoupling capacitors) between these three capacitors while ensuring COUT1B assists with the decoupling between COUT2 and COUT3. Ideal values cannot be determined without additional specific information such as Qg, ΔV, etc.
Inductance:- Inductance is often related to the layout of your PCB traces and any inductors or ferrite beads used. Keep trace lengths as short as possible and use proper layout techniques to minimize parasitic inductances.
Recommendation:jeffyj98
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- Datasheet: The easiest way to obtain Qg is to refer to the datasheet of the specific transistor you are using in your design. Most datasheets will have a section that lists the gate charge under typical operating conditions.
- Manufacturer: If the datasheet does not provide clear information, you may contact the manufacturer for more details or ask for application notes that might include gate charge information.
Voltage Droop (ΔV):- Application Requirements: Consider what your specific application can tolerate in terms of voltage variations without affecting performance. This might be defined by the minimum operating voltage of the load or by signal integrity concerns.
- Simulation: You can use electrical simulation software to model your circuit and observe the voltage at the output capacitor during switching events. Adjusting parameters within the simulator can help determine a feasible ΔV for your design.
- Experimentation: If simulation is not possible or practical, building a prototype and measuring the voltage droop during operation with various load conditions can give you a real-world sense of an acceptable ΔV.
Example of Finding ΔV:jeffyj98
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