5V Buck-Boost (Positive-to-Negative) Regulator – Design Note 49
Design note for a +4.5V to +40V input to -5V output buck-boost regulator using the LT1074 switching regulator, supporting output currents up to 3.5A.
Overview
This design note describes a positive-to-negative buck-boost converter based on the LT1074 switching regulator IC. The circuit accepts a DC input voltage from 4.5V to 40V and generates a regulated -5V output. The design supports a maximum output current of 1A at 4.5V input, increasing to 3.5A at 40V input. Operating at a 100kHz switching frequency, the regulator includes thermal protection and current limiting. The document provides a full schematic, bill of materials using off-the-shelf parts, and performance data including line and load regulation specifications.
Use Cases
- Negative voltage rail generation for analog circuits
- Industrial power supplies
- Telecommunications equipment
- Battery-powered systems requiring negative bias
Topics
Referenced Parts
CKO5BX473K
AVX
C4 1 CKO5BX473K Cap, Ceramic, 0.047μF, 100V AVX
CKO6BX103K
AVX
C3 1 CKO6BX103K Cap, Ceramic, 0.01μF, 100V AVX
CTX 25-5-52
Coiltronics
L1 1 CTX 25-5-52 Inductor, 25μH, 5A Coiltronics
CTX5-5-FR
Coiltronics
L2 1 CTX5-5-FR Inductor, 5μH, 5A Coiltronics
LT1074CT
Linear Technology
VR1 1 LT1074CT Switching Regulator, 100kHz LTC
UPL1V390MAH
Nichicon
C5 1 UPL1V390MAH Cap, Alum Elect, Low ESR, 39μF, 35V Nichicon
6038B-TT
Thermalloy
HS2 1 6038B-TT Heat Sink Thermalloy
7020B-MT
Thermalloy
HS1 1 7020B-MT Heat Sink Thermalloy
LXF10VB272M12X30LL
United Chemi-Con
C2 1 LXF10VB272M12X30LL Cap, Alum Elect, Low ESR, 1000μF, 10V United Chemicon
100V
AVX
C4 1 CKO5BX473K Cap, Ceramic, 0.047μF, 100V AVX
100V
AVX
C3 1 CKO6BX103K Cap, Ceramic, 0.01μF, 100V AVX
35V
Nichicon
C5 1 UPL1V390MAH Cap, Alum Elect, Low ESR, 39μF, 35V Nichicon
50V
Nichicon
C1 1 UPL1H221MPH Cap, Alum Elect, Low ESR, 220μF, 50V Nichicon
| MBR745 | Motorola | D1 1 MBR745 Diode, Schottky, 7A, 45V Motorola |
| UPL1H221MPH | Nichicon | C1 1 UPL1H221MPH Cap, Alum Elect, Low ESR, 220μF, 50V Nichicon |
| CKO5BX473K | AVX | C4 1 CKO5BX473K Cap, Ceramic, 0.047μF, 100V AVX |
| CKO6BX103K | AVX | C3 1 CKO6BX103K Cap, Ceramic, 0.01μF, 100V AVX |
| CTX 25-5-52 | Coiltronics | L1 1 CTX 25-5-52 Inductor, 25μH, 5A Coiltronics |
| CTX5-5-FR | Coiltronics | L2 1 CTX5-5-FR Inductor, 5μH, 5A Coiltronics |
| LT1074CT | Linear Technology | VR1 1 LT1074CT Switching Regulator, 100kHz LTC |
| UPL1V390MAH | Nichicon | C5 1 UPL1V390MAH Cap, Alum Elect, Low ESR, 39μF, 35V Nichicon |
| 6038B-TT | Thermalloy | HS2 1 6038B-TT Heat Sink Thermalloy |
| 7020B-MT | Thermalloy | HS1 1 7020B-MT Heat Sink Thermalloy |
| LXF10VB272M12X30LL | United Chemi-Con | C2 1 LXF10VB272M12X30LL Cap, Alum Elect, Low ESR, 1000μF, 10V United Chemicon |
| 100V | AVX | C4 1 CKO5BX473K Cap, Ceramic, 0.047μF, 100V AVX |
| 100V | AVX | C3 1 CKO6BX103K Cap, Ceramic, 0.01μF, 100V AVX |
| 35V | Nichicon | C5 1 UPL1V390MAH Cap, Alum Elect, Low ESR, 39μF, 35V Nichicon |
| 50V | Nichicon | C1 1 UPL1H221MPH Cap, Alum Elect, Low ESR, 220μF, 50V Nichicon |