LP2985-30 application check-Important!

Sulyn ZHANG

Other Parts Discussed in Thread: LP2985

Hi Team,

My customer which is top power automation customer is using our LP2985-30, they want to double check with us that if these is some problem with their schematic and application? Pls see below schematic, customer use a 1uF cap at the R14 position. And LP2985-30 will always work at about 70C temp, will this be stable or is these any risk to use like this? Thanks a lot for your support!

If these is risk, can you help give some recommended schematic?

Best regards,

Sulyn Zhang

over 8 years ago

0 Sulyn ZHANG over 8 years ago

TI__Expert 8700 points

Hi Team,
Can anyone help look into this application question? Thanks a lot!

Best regards,
Sulyn Zhang

0 Donald Jones over 8 years ago

TI__Mastermind 22610 points

Not directly under my umbrella, but close enough...

1) The 10nF capacitor from the Vout pin to the Bypass pin is not a good idea. That will feed any noise from Vout back into the band-gap circuitry which is positive feedback. This could lead to excessive ringing, or oscillation.

2) I don't see any Cout, so I can't comment beyond that it's not shown here. Cout should be at least 2.2uF direct from the Vout pin to the GND pin

3) The 1uF from Bypass to GND (R14 RES) is a huge value. Expect extended start-up times.

Please refer to the schematic in "Section 8.1.1 Typical Application" in the LP2985 datasheet.

www.ti.com/.../lp2985-30.pdf

0 Sulyn ZHANG over 8 years ago in reply to Donald Jones

TI__Expert 8700 points

Hi Jones,

Many thanks for your support!

Best regards,

Sulyn zhang

Power management

Power management forum

LP2985-30 application check-Important!