TPS7A7300: Feedforward Capacitor Value

Mark Ackerson

Part Number: TPS7A7300

Customer is using TPS7A7300 to power a cell modem. The VDD_CELL rail has 2 x 100uF 1210 package ceramic capacitors. These are big ceramics (GRM32ER61A107ME20L). What should the feed-forward capacitor value be? The data sheet states "For output capacitors from 47 μF to 200 μF a feed-forward capacitor of at least 220 pF must be used." Customer is using a 1 uF Cff.

They are having an issue that the current draw of the cell modem through the TPS7A7300 is pulling down the 5V rail and causing processor reset or lock-up.

Any design suggestions here? I can send schematics via email.

Thanks,
Mark

over 7 years ago

0 Ryan Eslinger over 7 years ago

TI__Guru 55940 points

Hi Mark,

The maximum recommended Cff is 100 nF.

Could you help me better understand the conditions of the current draw and output voltage droop? How much current is the modem pulling? Is it pulsed or constant? Please provide a scope shot of Vin, Vout, and Iout.

Very Respectfully,

Ryan

0 Ryan Eslinger over 6 years ago in reply to Ryan Eslinger

TI__Guru 55940 points

Hi Mark,

Since it has been several weeks without a reply, I assume that this thread is resolved. If this is not correct, please feel free to post again.

Very Respectfully,
Ryan

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TPS7A7300: Feedforward Capacitor Value