TPS548B22: Bode plot check

Will Wang47

Part Number: TPS548B22

hi team,

Customer is using TPS548B22 in their project and they find the bode plot as below, could you help check if this is OK? Main concern points are:

1. three times cross the zero line;

2. phase margin is very high when cross the zero line.

Could you help comments?

Best Regards,

Will

over 5 years ago

0 Alec Biesterfeld over 5 years ago

TI__Expert 5310 points

Hi Will,

Could you please share the schematic? I would be happy to provide feedback and review the schematic for stability criteria.

Please also refer to the following application note for the Bode plot analysis of DCAP3 parts:

https://www.ti.com/lit/an/sluaaf4/sluaaf4.pdf?ts=1632933768021&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS548B22

In general, in the DCAP3 control topology, the modulator senses the output voltage node and uses a comparator, which in theory has infinite bandwidth. This can lead to bode plots in which the phase does not necessarily cross zero and the gain crosses over multiple time. Please refer to sections 8.2.3.3.1 for minimum output capacitance and table 7 in the product datasheet as these are the primary adjustments for stability.

Regards,

Alec Biesterfeld

Power management

Power management forum

TPS548B22: Bode plot check