LM5146: Suggestion on Capacitor/Inductor/Resistor for COMP

Jack Shen2

Part Number: LM5146
Other Parts Discussed in Thread: LM5145

Dear,

We are using LM5146 with the PD controller. The output voltage will be different depending on the configure.

Here is the list of different output voltage

OUTPUT	5V	3A
	9V	3A
	15V	3A
	20V	2.25A

The frequency is set to 400khz
The input voltage is 37V ~ 54V.
FB pin is using 200k and 38.3K resistors.

Since in this application, the output voltage will be different, may I have your suggestion on the values of the capacitor/Inductor/Resistor for COMP pin?

Thank you.

over 3 years ago

0 Timothy Hegarty over 3 years ago

TI__Guru 73072 points

Hi Jack,

I recommend using the LM5145 quickstart calculator to derive component values. Note the effective output capacitance will vary with voltage (for ceramic), so this affects compensation.

Regards,

Tim

0 Jack Shen2 over 3 years ago in reply to Timothy Hegarty

TI__Expert 4445 points

Hi Tim,

Thanks for the comments.

Does that mean we cannot use one fix values of capacitor/inductor/resistor for COMP pin to meet different output voltages?

Thanks.

Jack

+1 Timothy Hegarty over 3 years ago in reply to Jack Shen2

TI__Guru 73072 points

Hi Jack,

It shouldn't be a problem. Just design the compensation for max Vout (min Cout value) and crssocheck the lower Vout setpoints where Cout is higher. You can keep the upper FB resistance constant so that the compensator is unaffected.

Regards,

Tim

0 Jack Shen2 over 3 years ago in reply to Timothy Hegarty

TI__Expert 4445 points

Got it. Thank you very much for the support.

0 Timothy Hegarty over 3 years ago in reply to Jack Shen2

TI__Guru 73072 points

Thanks for the question.

Power management

Power management forum

LM5146: Suggestion on Capacitor/Inductor/Resistor for COMP