SLVSCM8D May 2015 – August 2021 TPS61088
For good input voltage filtering, TI recommends low-ESR ceramic capacitors. The VIN pin is the power supply for the TPS61088. A 0.1-μF ceramic bypass capacitor is recommended as close as possible to the VIN pin of the TPS61088. The VCC pin is the output of the internal LDO. A ceramic capacitor of more than 1.0 μF is required at the VCC pin to get a stable operation of the LDO.
For the power stage, because of the inductor current ripple, the input voltage changes if there is parasite inductance and resistance between the power supply and the inductor. It is recommended to have enough input capacitance to make the input voltage ripple less than 100mV. Generally, 10-μF input capacitance is sufficient for most applications.
DC bias effect: High-capacitance ceramic capacitors have a DC bias effect, which has a strong influence on the final effective capacitance. Therefore, the right capacitor value must be chosen carefully. The differences between the rated capacitor value and the effective capacitance result from package size and voltage rating in combination with material. A 10-V rated 0805 capacitor with 10 μF can have an effective capacitance of less 5 μF at an output voltage of 5 V.