LT1970A ESD protection

Just following up, surely the designer would know this info?

Hi Edirol,

Good day!
Thank you for having interest in using LT1970A.
On the first paragraph, not sure if the enable line will still work on the condition where VEE and VCC are turned off.

What's the condition on your V+ and V- pins when the VCC and VEE drops to zero? Will it be okay to share your schematic to us? and the actual application?

For +in and -in, I don't think you'll have a problem since it's stated on the abs max that it can reach up to 36V given you limit the current to 10mA:

For the rest of the pins such as +/-VSense, filter, etc. your limitation is on the V+ and V- pins.
How long do you think the off condition on your application will last? Since, even if you have a very low current I can't guarantee the robustness of the part because it still violates the abs max rating in terms of voltage. and what's the battery voltage level? I may need this information as I check in with the designer.

For the inputs (+IN and -IN), there's no information if there's an ESD protection but on page 8 it stated that if in your circuit there's a chance that the input may go below VEE-0.3V you may need an external Schottky Diode to provide proper clamping. 

Thanks Edirol.

Best Regards,
Dann

HI Dann, 

Thanks for your reply! The circuit design is similar to the boosted design of DC453bf.pdf. While the circuit is off, the maximum battery voltage I am expecting is 5V. I would hope that this could be sustained indefinitely if the user accidentally turns off the circuit while the battery is still connected,

To answer your questions, the V+ and V- pins will also go to zero since the power will be off to the entire circuit. This means that the current sense pins common mode would also exceed these values (I have a 20k/20k voltage divider halving the VSense+ and VSense- common mode maximum to 2.5V when 5V battery is connected). 

I am also concerned about the output pin (whether it does go to high impedance output or not) when the device is not powered. As per DC453b there is an output resistor here (in my case 40 ohms). I can maybe disconnect the output with a relay when the power is turned off if this is going to be a problem.

You are correct that the +IN and -IN pins should be safe according to the datasheet. I dont expect a voltage below VEE in this situation.

Thanks in advance,

Just following up on this ? We are about a month away from production so this is getting pretty critical. Please let us know. Thank you.

Hi Edirol,

Apologies for the delay in response but thank you for the patience.

I checked the LT1970A but there doesn't seem to have some characterizations on the output current capability, especially during power off. Therefore I won't be able to guarantee if this will be good in the long run because we'll still violate the abs max rating.

The safest is to apply the relay in the output and disconnect it during power off operation.
Thank you!

Best Regards,
Dann

Hi Edirol,

Apologies for the delay in response but thank you for the patience.

I checked the LT1970A but there doesn't seem to have some characterizations on the output current capability, especially during power off. Therefore I won't be able to guarantee if this will be good in the long run because we'll still violate the abs max rating.

The safest is to apply the relay in the output and disconnect it during power off operation.
Thank you!

Best Regards,
Dann

Hi Dann, Okay great I will proceed with this solution.