LMR38010-Q1: High Vout operation with Electrolytic caps?

Allen Wachter

Part Number: LMR38010-Q1

My customer has two applications for the LMR38010-Q1 where the output voltages are 20V and 30V. They are looking at using an electrolytic capacitor output instead of ceramic capacitors because the ceramic caps derate so much with DC bias. The data sheet defines a minimum output capacitance (15μF after derating – page 19, Figure 9-1, using 24V out). The assumption is the table assumes ceramic capacitors are used. The issue with an electrolytic capacitor is the cap esr is much higher than a ceramic cap. So two questions:

1.) Is there addition information or equations available for the LMR38010-Q1 so we can see how higher ESR output capacitors impacts stability?

2.) Assuming some ceramics are required, do we have a formula or procedure for mixed electrolytic & ceramic operation?

Thanks!

over 1 year ago

0 Frank De Stasi over 1 year ago

TI__Guru 64095 points

Hello

I will speak with the application engineer for this device and get back to you as soon as possible.

Thanks

0 Frank De Stasi over 1 year ago in reply to Frank De Stasi

TI__Guru 64095 points

Hello

You can use a combination of ceramic and Al.

In this case you could try a

0 Frank De Stasi over 1 year ago in reply to Frank De Stasi

TI__Guru 64095 points

Hello

If you can tell me your input voltage, output voltage, load current, and switching frequency

I can run a simulation with a combination of ceramic and Al. output capacitors.

Thanks

0 Allen Wachter over 1 year ago in reply to Frank De Stasi

TI__Expert 6450 points

Hello Frank,

Vin is regulated 56V, Vout is 20V (and 30V) at 1A max. Switching frequency is 500kHz.

Can you come up with a solution which use a ceramic and electrolytic parallel combination on the output?

Do we have any apps notes for calculating an equivalent capacitance for this parallel combination? I seem to remember something like this a while ago.

Thanks!