L4970a Output Oscillates

[adco]

Posted on March 04, 2014 at 09:46

I need the following: 24V vehicle input. Allow for 28V. 13.8V @ 10A output. I used an L4970a. My circuit delivers the load, no problem.

On initial switch on with no load, the output is stable. When I place a load up to 10A, it works. When I remove the load, the output oscillates between Vin and 7.5V at 13Hz (75mS) with a sawtooth function. If I place the load on again, it works perfectly.

I searched on the internet and saw a suggestion that I place a load of 0.2A across the output as an offset stabiliser. That didn't work. It also generates another 2.6W of heat. Not so good.

So, the problem occurs after a load is removed. I cannot guarantee that there will always be a load on the output.

I have followed the layout guide-lines from the ST app notes.

#l4970a

[SMuru]

HI,

I'm also having same issue. My input is 15V, output is 12/9Amp. I have tested with 1Amp load, that didn't work.