notbruno / 480W, 48V Buck Boost

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Variable Output Voltage Design

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2:14

Evaluating design adjustments.

Confirming voltage specifications.

Discussing component linking.

Confirming LTC3779 specifications.

Accessing knowledge base.

Reviewing the bill of materials.

Looking for "VFB reference voltage" in ltc3779.pdf

Looking for "Output voltage setting equation VOUT VFB resistive divider" in ltc3779.pdf

Looking for "VFB pin description" in ltc3779.pdf

Looking for "Loop compensation ITH component selection guidelines" in ltc3779.pdf

Looking for "PGOOD threshold relative to VFB regulation" in ltc3779.pdf

Looking for "SS pin soft-start description" in ltc3779.pdf

Looking for "VOUTSENSE pin function and remote sensing guidance" in ltc3779.pdf

Looking for "Output voltage range limitations and minimum on/off-time constraints" in ltc3779.pdf

Looking for "VFB reference voltage" in ltc3779.pdf

Looking for "Output voltage programming equation VOUT" in ltc3779.pdf

Looking for "VFB pin description" in ltc3779.pdf

Looking for "ITH compensation selection" in ltc3779.pdf

Looking for "PGOOD threshold" in ltc3779.pdf

Looking for "SS soft-start" in ltc3779.pdf

Looking for "VOUTSENSE pin function" in ltc3779.pdf

Looking for "minimum on-time off-time output voltage range" in ltc3779.pdf

Exploring adjustable output options.

Yes. This design can be made variable by changing the feedback divider around U1. Per best practice, the output voltage is set by the feedback resistors, so making one leg adjustable will vary VOUT.
Practical options:
  • Front-panel potentiometer:
    • Keep R10 fixed and replace R11 with a series fixed resistor plus a multi-turn pot to the output. Add “stopper” resistors to enforce safe min/max VOUT. This is the simplest way to vary VOUT.
  • MCU/DAC control:
    • Inject a controlled voltage/current into the FB node with a DAC (through a resistor or small summing amp). This avoids a mechanical pot and enables profiles/limits in firmware.
What to watch:
  • Compensation: Varying VOUT changes plant gain. You may need to retune the ITH network (R9, C11) for stability across the range.
  • Status thresholds: PGOOD/OV/UV thresholds track the FB ratio, so they will shift with adjustable VOUT.
  • Remote sense: Keep VOUT sense wiring as-is; do not route the divider wiper through long runs.
  • Range limits: Define hard min/max with fixed resistors so the pot/DAC cannot drive VOUT into unsafe regions.
  • Power/train limits: Ensure the chosen VOUT range stays within controller minimum on/off-time limits, inductor ratings, and MOSFET/diode voltage stress.
If you share:
  • Desired VOUT range (min/max)
  • Adjustment method (pot vs MCU/DAC)
  • Load current over that range
I can put together a concrete change proposal (values for R10/R11, pot value and end-stops, and any ITH tweaks), and then implement it in the project for you.
Give target range
Prefer potentiometer
Ask compensation impact
MCU/DAC control
Check controller limits
158 days
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SW1
R9
Resistance
10kΩ
BOTB_DRAIN
FREQ
BOOST2
TOPD_SOURCE
R6
Resistance
100 Ω
RUN
BOTC_SOURCE
SENSEN
BG2
PGOOD
BOTC_DRAIN
I_AVGSNSN
BOOST2
V_FB
BOOST1
I_AVGSNSP
TOPA_SOURCE
R7
Resistance
100 Ω
MODE
SW2
BOTB_SOURCE
PGND
SENSEP
R19
Resistance
100 Ω
R12
Resistance
100 Ω
ITH
SGND
PILLIN
SW2
V_OUTSNS
TG2
TOPD_DRAIN
D2
R10
Resistance
12.1kΩ
L2
Inductance
15uH
R8
Resistance
4mΩ
C444
Capacitance
10nF
R13
Resistance
4mΩ
C25
Capacitance
10uF
C9
Capacitance
.22 uF
C16
Capacitance
4.7µF
C12
Capacitance
10uF
C8
Manufacturer Part Number
GRM033R60J224KE15D
Designator Prefix
C
Capacitance
.22 uF
D1
C10
Capacitance
10uF
C14
Capacitance
220pF
C11
Capacitance
100pF

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480W, 48V Buck Boost

480W, 48V Buck Boost thumbnail
99% Efficient 480W, 48V Output, 20V to 100V Input Buck-Boost Converter,

Properties

Properties describe core aspects of the project.

Pricing & Availability

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