LM2576: Will LM2576 be damaged if reverse voltage is applied to OUTPUT pin(Pin2)?

Tanaka-san,

I don't believe VOUT > VIN will cause an issue on this part but I will double check and return with an answer tomorrow or the next day.

Typically VOUT > VIN can cause the device to sink current to bring the output voltage down but this device is non-synchronous so this is not an issue.

The other typical issue is that the body diode of the high-side FET will conduct which will push current from VOUT to VIN. But this device has an internal BJT, not a MOSFET so I don't think this should be an issue either.

I'll let you know when I confirm.

-Sam

Dear Samuel san,

I appreciate your rapid response.

>We do not recommend this.

I understand it is possible that "reverse voltage", which here means

the condition that the voltage higher than the vltage on VIN pin(Pin1) is applied to OUTPUT pin(Pin2),

damages LM2576.

>There is a possibility that the base-emitter junction can break down and create a path from base to collector.

And, please let me have one more question.

Is it possible to guess what will happen if "a path from base to collector" is generated?

According to the block diagram shown on the datasheet, base is connected to DRIVER of the transistor,

so, I easily guess that internal circuits of LM2576 will be broken.

But if possible, I want to know how the circuit will be broken, e.g. Pin2 will be short-circuited to GND, etc.

The answer may be "it is difficult to know what happens inside LM2576", and if so, please let me know it

and no further investigations are needed. I'll close this question.

Best regards,

Shinsuke Tanaka

Dear Samuel san,

I appreciate your rapid response.

I understand that the "reverse voltage" may damage BJT and DRIVER inside LM2576.

>This current may cause damage to the BJT (and driver) which may result in an open or short circuit from VIN to OUTPUT and/or VIN to GND.

I'm sorry for my repeated questions, but please let me have one more question.

Hopefully this will be the last question on this topic.

Do you think there is a possibility that the "reverse voltage" may cause short-circuit between OUTPUT pin(Pin2) and GND pin(Pin3)?

The short-circuit is not included in your response "open or short circuit from VIN to OUTPUT and/or VIN to GND",

so I want to clarify this, just in case.

The reason why I ask this is as follows;

  On our failed product, it was found that LM2576 is broken and the condition of it is that OUTPUT pin(Pin2) is short-circuited to GND.

     Note : Please make sure that the failure on the LM2576 was NOT caused by the problem of LM2576 itself.
                We conclude that the failure on LM2576 was caused externally.

  I now guess that the short-circuit between LM2576 OUTPUT pin(Pin2) and GND was cause by the "reverse voltage"
  considering any other conditions on our failed product. And I want to confirm if my guess is not irrevant through the above question.

Best regards,

Shinsuke Tanaka