Adjusting Boost Converter Voltage

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Based on knowledge base guidance for designing feedback networks and the TPS61085 datasheet:
  • The TPS61085’s internal reference (V_FB) is 1.229 V (from the datasheet).
  • In our schematic, the lower feedback resistor (R2) is 18.2 kΩ.
  • The output voltage equation is:
    VOUT=VFB(1+R1R2)V_{OUT} = V_{FB}\Bigl(1 + \frac{R1}{R2}\Bigr)
    Rearranged for R1:
    R1=R2(VOUTVFB−1)R1 = R2\Bigl(\frac{V_{OUT}}{V_{FB}} - 1\Bigr)
  • Plugging in V_OUT = 8 V, V_FB = 1.229 V, and R2 = 18.2 kΩ:
    R1=18.2 kΩ×(81.229−1)≈100 kΩR1 = 18.2\,\text{kΩ}\times\bigl(\tfrac{8}{1.229}-1\bigr)\approx 100\,\text{kΩ}
    (Calculator result: 1.0027×10^5 Ω)
Thus, choosing a standard 100 kΩ resistor for R1 ensures the booster regulates to 8 V.
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@library find a 100 kΩ 0603 resistor for R1

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Here are the top 3 matching 100 kΩ, 0603 resistors:

Table

Part NameManufacturerResistanceTolerancePower RatingPackageAvailabilityLinkDatasheet
CRCW0603100KFKEAVishay Dale100 kΩ±1%0.1 W0603Digi-Key, Mouser, Arrow, LCSCView in LibraryPDF
RMCF0603FG100KStackpole Electronics Inc100 kΩ±1%0.1 W0603Digi-Key, MouserView in LibraryPDF
RMCF0603FT100KStackpole Electronics Inc100 kΩ±1%0.1 W0603Digi-Key, Mouser, ArrowView in LibraryPDF
Recommendation: All three are 100 kΩ ±1% thick-film resistors in 0603 with 0.1 W rating. The Vishay CRCW0603100KFKEA has the highest usage count and broadest distributor support, making it a robust choice for R1.
Use Vishay resistor
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Next decoupling capacitor
Cheapest resistor choice
C2
Capacitance
10uF
C3
Capacitance
1.1nF
C5
Capacitance
1uF
C1
Capacitance
10uF
C4
Capacitance
100nF
C6
Capacitance
10uF
VIN
12V OUT
12V
R2
Resistance
18.2kΩ
12V
FB
VIN
L1
Inductance
3.3uH
VIN
GND
R3
Resistance
51kΩ
IC1
FB
D1
VIN
GND
R1
Resistance
158kΩ
VIN

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    TPS61085 Reference design.png

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    TPS61085 Reference design tiHX

    TPS61085 Reference design tiHX thumbnail
    This is a power module based on a TPS61085 voltage booster IC with an output voltage of 12V 3A(max) #boost #power #dcdc #ti #referenceDesign #powermanagement #texas-instruments #template

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