JAJU299A June 2017 – January 2023
The input voltage that can be applied to an integrated circuit (IC) operating in the inverting buck-boost topology is less than the input voltage for the same IC operating in the buck topology. The reason for this difference is because the ground pin of the IC is connected to the (negative) output voltage. Therefore, the input voltage across the device is VIN to VOUT, not VIN to ground. Thus, the input voltage range of the TPS82130 is 3 to 17 V + VOUT, where VOUT is a negative value.
The output voltage range is the same as when configured as a buck converter, but negative. The output voltage for the inverting buck-boost topology must be set between –0.9 and –6 V. The output voltage is set in the same way as the buck configuration, with two resistors connected to the FB pin. Use the same equation in the TPS82130 data sheet to set the output voltage, keeping both VOUT and VFB as positive values. The TIDA-01457 design sets the output voltage at –5 V, which gives an input voltage range of 3 to 12 V. However, it is not recommended to use a 12-V input voltage because voltage tolerances on the input supply can violate the recommended operating range of the TPS82130.