LM2598SX-12/NOPB Not Regulating to 12V

Rob Greenewald

Hello, I am trying to regulate from 24V to 12V using the LM2598SX-12/NOPB. I followed the design process in the datasheet, but I am getting an output that wanders from 1.8V to 3.2V. My estimated max current output is 750mA @ 12V. Below is a diagram of my circuit.

BOM:

C8 = Panasonic EEH-ZA1H680P

C13 = Kemet C0805C104K3RACTU

C9 = Vishay / Sprague 595D127X0020R2T

D2 = Diodes Inc ZHCS2000TA

L1 = Bourns SRN1060-151M

Any help getting the output to 12V is appreciated. Thank you,

Rob

over 12 years ago

0 Richard Elmquist over 12 years ago

TI__Mastermind 45250 points

Rob,

Can you verify that the device is the 12V fixed version. It is almost acting like this is the adjustable version.

Can you post the switching waveforms that you are seeing the output?

I will do some more research and get back to you if I have further questions.

Richard Elmquist

0 YangZhang over 12 years ago in reply to Richard Elmquist

TI__Genius 11085 points

Would you also measure the input voltage right at the input pins of the IC and the input current to the IC? Just to make sure there is no damage or mal connection on the IC or board.

Posting SW node waveform would help us debuging.

Yang

0 Rob Greenewald over 11 years ago in reply to YangZhang

Prodigy 190 points

Hi Yang, I got the switcher working. I just have to remove the soft start capacitor, and adjust the timing on the other switcher that it was powering. Thanks,

Rob

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LM2598SX-12/NOPB Not Regulating to 12V