LM2576HV: Problems with used on/off key for LM2576HV

Reza sD

Part Number: LM2576HV

hello,
We use a LM2576HV-Adj IC for power supply. Cin 100uf/ Cout 330uf/ L 330uH/ Diode SK39A/ Vin 60V/ Vout 12V.
we used one switch for on/off the output voltage. we connect pin5 of LM (ON/OFF pin) with R 4.7K to Vin and with Switch to GND.

Applying 60V input:

When the switch is connected, pin 5 from the IC is connected to ground and we have 12V output voltage. By disconnecting the switch, the output voltage is zeroed correctly.
But:When we reconnect the switch; to have voltage at the output, a problem occurs and the IC burns out and also draws 1 amp from the input.
We have installed only one LED series a resistance of 10 kg for the output load.

What is our problem? Is 60V too high for the ON/OFF pin IC?
Thanks

over 5 years ago

0 Andy Chen over 5 years ago

TI__Mastermind 34875 points

Hi Reza,

Is the diode SK39 still function OK while IC burn out?

Please the Pin2 Output waveform at about 48V input to see if there is too high spike and over shoot.

How about saturation current of 330uH?

B R

Andy

0 Andy Chen over 5 years ago

TI__Mastermind 34875 points

Hi Reza

Do you fixed the problem?

B R

Andy

0 Reza sD over 5 years ago in reply to Andy Chen

Prodigy 130 points

Hi Andy,

Yes, diode SK39 still function OK . If we replace the IC, the output voltage will appear correctly with the new IC. (With Applying 60V input: When we reconnect the switch; to have voltage at the output, a problem occurs and the IC burns out and also draws 1 amp from the input.)(And interestingly, the IC does not heat up at all.)

We used an inductor with a current of 2 amps. Of course, we do not have a load at the output and we will not have any current flow. We have only one LED.

0 Reza sD over 5 years ago in reply to Andy Chen

Prodigy 130 points

Hi Andy
No fixed the problem.

We want to change the value of the inductor to 100UH- 3A, then perform the test again from 48 volts to 60 volts.
We will announce the result.
Thanks.

0 Andy Chen over 5 years ago in reply to Reza sD

TI__Mastermind 34875 points

Hi Reza,

Can you upload the PCB layout for checking?

B R

Andy

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LM2576HV: Problems with used on/off key for LM2576HV