The TPS7H1111 is optimized for a single tantalum output capacitor of 220 μF or two 100 μF capacitors. The complete range of acceptable capacitance, ESR, and ESL are specified in the Recommended Operating Conditions. Make note to verify the selected capacitors meet the requirements across all operating conditions. Additionally, a single 0.1 μF ceramic capacitor can be included. Place the one or more tantalum capacitors near the output of the TPS7H1111 and place the ceramic capacitor near the point of load.

ESR (equivalent series resistance) is an important parasitic element to take into account that varies significantly across frequency for capacitors. ESR values for tantalum capacitors are generally given at 100 kHz, and the values in the Recommended Operating Conditions table approximately correspond to values at 100 kHz. However, in reality the ESR at the loop crossover frequency is primarily what affects the stability of the TPS7H1111 control loop. The loop crossover frequency can be higher or lower than 100 kHz. Therefore, the range of ESR values can be considered a good guideline, but additional verification of stability is prudent.

Also note that the capacitance, ESR, and ESL requirements are for the entire bulk capacitance. If 2x100 μF capacitors each with 40 mΩ ESR and 2 nH ESL are used, the resulting capacitance is 200 μF with 20 mΩ ESR and 1 nH ESL. The single ceramic capacitor should not be taken into account when considering these ESR and ESL requirements.

Ceramic capacitors larger than 0.1 µF are generally not allowed due to their lower resonance frequency. This lower resonance frequency is likely within the loop bandwidth of the TPS7H1111 regulator (which can be nearly 10 MHz). Therefore, the low resonance point, combined with the low ESR, negatively impacts the loop bandwidth and device stability. The lower bandwidth negatively affects PSRR, therefore negating any potential benefit of additional ceramic capacitance.

However, if ceramic capacitors above 0.1 µF must be used, it is recommended the ceramic capacitor has a resonance frequency one to two decades above the loop bandwidth. Alternatively additional series resistance can be added to increase the ESR. This prevents a strong resonance point.

TI has measured gain and phase margin of various space grade capacitors to demonstrate good stability margin. See Section 9.3 for additional information.

When capacitors other than the standard bulk capacitance and a single 0.1 µF capacitor are utilized, it is recommended to simulate the capacitors and complete system. It is also suggested to create a Bode plot and perform load steps on the actual system to verify sufficient stability margin.