Negative Voltage Design with Buck Circuits: How to Generate Negative Voltage Using the TPS5430 as an Example
The TPS5430 is originally a synchronous step-down Buck converter that only generates positive voltages relative to ground. By redefining the chip’s reference ground potential, it can be reconfigured into an inverting Buck-Boost topology to produce a stable negative output voltage with respect to system ground.
Native Standard Positive-Output Buck Circuit of TPS5430 (Reference Benchmark)
Circuit Potential Reference
This is the native positive-output step-down Buck circuit provided in the TPS5430 datasheet, where all potentials are referenced to the system GND (0 V).
(Images sourced from Texas Instruments, TI)
Power Path
VIN (Pin 7) → PH (Pin 8) → Power Inductor L → Positive VOUT Terminal → Negative terminal of output capacitor connected to ground
Freewheeling Mechanism
The high-side and low-side MOSFETs operate synchronously. The high-side switch turns on to store energy, while the low-side MOSFET conducts for freewheeling. No external diode is required, and the synchronous topology delivers high efficiency.
BOOT Circuit
A 0.01 µF ceramic capacitor bridges BOOT (Pin 1) and PH to supply floating gate drive power for the high-side MOSFET.
Feedback Network
The upper divider resistor connects to the positive VOUT rail, the lower divider resistor connects to 0 V ground, and the divider midpoint feeds into VSENSE (Pin 4).
Negative Voltage Circuit Based on TPS5430
This circuit adopts the Inverting Buck-Boost architecture. It modifies the standard step-down TPS5430 to output a stable -5 V relative to system ground with a +5 V DC input, intended for negative rail power supply of analog circuits such as op-amps and DACs.
(Images sourced from Texas Instruments, TI)
Core Modification Principle
Connect the chip’s internal reference ground (GND pin + PowerPAD thermal pad) to the -5 V negative output rail instead of the system 0 V ground. Shifting the chip’s potential reference in this way achieves negative voltage generation.
Related Document
Related Part Number
Further Reading on Negative Voltage Fundamentals
- Negative Voltage Basics: What Is Negative Voltage?
- Negative Voltage Basics: Voltages in Communication Circuits
- Negative Voltage Basics: Why Op-Amp & Audio Analog Circuits Require Positive/Negative Power Supplies
- Negative Voltage Basics: Charge Pump Implementations
- Negative Voltage Basics: Positive and Negative Voltage Design for Buck Circuits
- Negative Voltage Basics: Negative Rail Supply for Precision Op-Amp AC Signal Amplification