LM5574, LM5575 / maximum soft start capacitance

Ryuji

Guru 20090 points

Other Parts Discussed in Thread: LM5574

Hello,

Is there soft start capacitance limitation for LM5574/5?
If there is, please let me know the maximum capacitance value.

Best Regards,
Ryuji Asaka

over 10 years ago

0 Anston Lobo over 10 years ago

TI__Genius 16025 points

Ryuji-san,

I need to check with the designer before I can provide a reply. Thank you for your patience.

-Anston

0 Anston Lobo over 10 years ago in reply to Anston Lobo

TI__Genius 16025 points

Ryuji-san,

It seems like you have a specialized application. What soft start time are you targeting and what capacitor value are you looking at? This will help us figure this out faster.

Thanks,

Anston

0 Ryuji over 10 years ago in reply to Anston Lobo

Guru 20090 points

Hello Anston san,

Thank you for the reply.
Capacitor value is 1uF.

Best Regards,
Ryuji Asak

0 Anston Lobo over 10 years ago in reply to Ryuji

TI__Genius 16025 points

Ryuji san,

I tested an LM5574 on a stock eval board with a 1uF SS capacitor at 25C with an input voltage of 18V and output of 5V under no load. The soft start time was 120msecs and there were no issues during startup. I've attached the scope shot showing this. I can only confirm that this works for the conditions mentioned. Hope this is sufficient.

Thanks,

Anston

0 Ryuji over 10 years ago in reply to Anston Lobo

Guru 20090 points

Hello Anston san,

Thank you very much for your support.
I understood.

Best Regards,
Ryuji Asaka

Power management

Power management forum

LM5574, LM5575 / maximum soft start capacitance