TPS650250: Any value in having feedforward capacitor

Reed,

For TPS650250 and most other PMICs, the compensation is internal as you pointed out.

With internal compensation, it is not always necessary to add a feed-forward capacitor, Cff, and it is not a common practice.

A couple devices have Cff recommended in the datasheet. The LM26480 comes to mind as an example.

However, for PMICs such as TPS650250 I would only recommend adding Cff if the load transient response is poor (too slow) or possibly if the output inductance and capacitance are modified heavily from the recommended values. If such changes are made, you would typically measure the frequency response of the regulator to determine if you have accidentally created a less stable circuit.

If you do determine Cff is needed for a DC-DC or LDO, feel free to review these App Notes for recommendations on how to use:

Feedforward Capacitor to Improve Stability and Bandwidth With Internally Compensated Converters

Pros and Cons of Using a Feedforward Capacitor with a Low-Dropout Regulator