TLV62585PEVM-030: Transient performance and CFF design

Tiger Yeh

Expert 4535 points

Part Number: TLV62585PEVM-030
Other Parts Discussed in Thread: TPS56637

Hi~

Currently, customer is evaluating TLV62585XDRL and found its transient is not good enough.

His test condition are

1. Input: 5V or 3.3V

2. Output: 1.2V/3A

3. Inductor: 1uH

4.Output cap: 22uF x2

5. Transient from 0A to 3A

This result 80mVp-p and add 22pF will improve to 68mVp-p

And 33pF is around 65mVp-p.

Is there any suggestion for LC and CFF design?

over 5 years ago

0 Excel Regidor over 5 years ago

TI__Mastermind 28756 points

Hi Tiger,

Can you share the resistor divider across FB so I can give recommendation on the max Cff value?
What is the max Vp-p specs?

Best regards,
Excel

0 Tiger Yeh over 5 years ago in reply to Excel Regidor

TI__Expert 4535 points

Hi Excel,

Currently, customer is using 100K-100K for 1.2V output.
Actually, it is better to have table for different output configurations.

The max Vp-p spec is +/-5% of Vout and it is better to have enough margin.

0 Excel Regidor over 5 years ago in reply to Tiger Yeh

TI__Mastermind 28756 points

Hi Tiger,

Thanks for your quick response.

There are two options to reduce the voltage deviation during transient load: 1) increasing Cout < 100uF and/or 2) increase Cff. In both cases, loop stability needs to be checked so phase margin => 45deg. I attached the app note for optimizing the Cff according to your application.

Best regards,

Excel

feedforward cap_slva289b.pdf