(ADR3533)What will happen if Vout short to GND?

Hi!

Can anybody help about this?

Best regards.

Kawa

Hi Phil

Thank you for your reply!

Our customer will use ADR3533 for automotive BMS.

The OEM is Japanese famous OEM and our customer have to explain to the OEM what will happen when the output short to GND.

This is kind of FMEA.

So answer to your question, 

  1) How long? How often?

      => I'm not sure about this but I think more than few sec. I mean this is FMEA so it will short to GND forever.

Also their is no specification for the current when Vout short to GND.

So I cannot calculate the temperature.

Anyway , I will wait the persons answer who knows the device structure.

Please do not hesitate asking me about our customer application.

Best regards

Kawa

Hi Kawa-san,

I need to verify this question to the person who knows the device structure. But to give you some inputs, the current output of the device will be maximum when the output is shorted to ground. ADR3533 has max current source of 10 mA while some datasheets also shows short circuit to ground value but that is not necessarily the same. Will the device break? it depends on how long and how frequent , some of our references datasheet specify the short circuit to ground duration or how long will it able to survive when shorted to ground in the absmax section , some datasheets say "indefinite".

Other way to look at this is to make sure we don't violate the absmax. If VIN is 5 volts and let say current out is 10 mA. Then we have 50 mW. Theta-JA of 8 lead MSOP is 132.5 degC/W. Then we will have rise in junction temperature of approximately 7 deg. If we add this number to your ambient temperature, the result should be in the range of the junction temperature range, for ADR3533 it should not be more than 150 degC max.

I would  appreciate if you could share what is your customer application is and what is the nature of the short to ground event? How long, how often and why will it happen?

Regards,

Phil

Hi Phil.

I understood what you said.

So can you tell us the current value when the output connect to GND?

Best regards,

Kawa

Hi Kawa-san,

I have to correct my statement on my previous reply. The 10 mA is minimum spec not maximum, I overlooked the number here. The maximum current can be very much higher than 10 mA.

On the other hand, if the output will be connected to ground for a long time, it will probably break the part forever.

Regards,

Phil

Hi Phil

Also why did you say "On the other hand, if the output will be connected to ground for a long time, it will probably break the part forever."?

Is this because temperature?

What will happen if Ta is low enough?

And which circuit will broke?

Would the output stage circuit will broke?

Best regards.

Kawa

Hi Phil

I measured ADR3533 Vin current when the output short to GND.

The result was 50~60mA.

Also the device didn't broke.

So the wattage will be maybe 300mW.

Junction temperature will rise 40 deg.

So this means ADR3533 will survive if the Ta is low enough.

Is this correct?

I need more detail if the device will broke when the output shorted to GND.

Best regards.

Kawa

Hi Phil

Can you help about this?

Best regards.

Kawa

Hi Kawa-san,

Sorry for the delay.

The ~60 mA you’re getting is valid. This short to ground current is the IDS of the output transistor which is based on the transistor size, VGS, and VDS applied during the short circuit event. At ambient, the device will likely to survive assuming the duration is relatively short. But it will also likely to cause reliability issue.

Regards,

Phil

Hi Phil

Thank you for your reply.

So you mean the Pch-FET at the output side will maybe finally broke?

Best regards.

Kawa