TPS568215: Max Output Capacitance

T Kishi

Genius 4425 points

Part Number: TPS568215

My Customer has question.

TPS 568215 has Coutmax of 500 uF.
(Data Sheet Table 5)

Is there any problem when adding more capacity?
The customer must attach about 1000 uF depending on load demand.

Regard

T Kishi

over 7 years ago

0 Gavin Wang (Zejing) over 7 years ago

TI__Expert 3480 points

Bigger output cap may bring the problem for loop. The bigger output cap is, the lower cross frequency is.

0 Vental Mao over 7 years ago

TI__Expert 5745 points

More cap means double pole will push to low frequency. The cross frequency will decrease, will cause loop unstable.
Why your customer want to use such a big cap?

0 T Kishi over 7 years ago in reply to Vental Mao

Genius 4425 points

Hi Vental

Since the load is an FPGA, it is a request of the FPGA.

0 Anthony Lang over 7 years ago in reply to T Kishi

TI__Expert 4875 points

Hi T Kishi,

A workaround solution for the loop is to use a smaller inductor corresponding. Also, try to select a longer soft start time to avoid current limit during soft start. Thanks!

0 Vental Mao over 7 years ago in reply to T Kishi

TI__Expert 5745 points

Does the customer concern about the load transient? or Vout ripple

0 T Kishi over 7 years ago in reply to Vental Mao

Genius 4425 points

Hi Vental

Since it is a request of the FPGA side, I think that both "transient" and "ripple" are considered.

0 Vental Mao over 7 years ago in reply to T Kishi

TI__Expert 5745 points

OK, You can suggest customer to measure his loop respond to double check he can increase cap a little(such 600uF) if the transient and ripple is not good.

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TPS568215: Max Output Capacitance