LM5118: How to slow a response speed of feedback in LM5118

Hirotoshi Mitsui

Part Number: LM5118

Dear,

I am trying to generate FB signal for LM5118 with LTC2645 (12bit PWM to Vout DAC) in order to output multi-level voltage on buck-boost.

I would like to slow a response speed of LM5118 but I could not make it by changing a smaller gain of error amplifier (COMP).

Could you tell me how a response speed of feedback should be slowed in LM5118?

Kind regards,

Hiro

over 4 years ago

0 Brigitte over 4 years ago

TI__Guru 65340 points

Hello Hiro,

In general I recommend to close the loop with standard resistor dividers and then use the method described in this short article: Adjusting VOUT in USB Type-C™ and wireless charging applications, part 2 - Power management - Technical articles - TI E2E support forums

If you want to slow down the reaction to the feedback node, you could add a small capacitor (in the pF range) from FB to GND. Be careful this will cause a slow reaction on load transients on the output and could cause instability.

0 Hirotoshi Mitsui over 4 years ago in reply to Brigitte

Prodigy 20 points

Hello Brigitte,

Sorry for the late reply. Thank you for giving any information.

It was hard for me to build a stable feedback with DAC module or adding a small capacitor between FB and GND.

I could make a solution with digital potentiometer generating FB signal.

Kind regards,

Hiro

Power management

Power management forum

LM5118: How to slow a response speed of feedback in LM5118