THS4531: Input over voltage protection

Hello Mehri,

While this may help with your input current limitation, you will still need to be wary of exceeding the input pin ratings of (VS–) – 0.7 to (VS+) + 0.7.

Best,

Hasan Babiker

Dear Hasan,

Then what is the purpose of internal protection diode?

It does not make sense to me. If we limit their current they should not burn meanwhile we are safe.

regards,

Hi Mehri,

can you show a schematic?

Kai

Morning Mehri

The first set of R's should be adequate to protect the current into the input pins for 60V input. That spec is set by the ESD steering diodes from each pin up and down to the supplies. You do need to be a little careful about losing phase margin due to input C and the feedback network, I tried to explain all that in this designing attenuators article, 

https://www.planetanalog.com/are-inverting-attenuators-with-voltage-feedback-op-amps-inherently-unstable-and-why-might-you-want-to-apply-them-insight-11/

Thanks, Michael,

Can I always consider that there is a protection diode on the inputs when I see the absolute maximum input voltage as below?

Vin max = VS(+) + 0.2 V or 0.7V and VS(-) - 0.2 V or 0.7V

I think this 0.2V or 0.7V implies on the presence of diode, isn't it?

Best regards,
Mehri

Hello Mehri,

This is correct, the 0.7V limit on the abs max implies diodes on the pins. I would not recommend thinking of these as protection diodes though as these are diodes aren't designed to handle continuous currents greater than 10mA (as shown in the abs max). The diodes are designed for ESD signals, typically meant for higher currents in the range microseconds or less.

Best,

Hasan Babiker