ESD protection for Temperature Diode

[alpha999]

Is there any way to protect a normal diode between two pads that is intended for temperature measurements ?

If normal esd diode to vcc/gnd and power clamp protection style is used there will always be the problem that if the device is off and you inject a current for calibration of the temperature diode that the current can go parallel to the temperature diode through the ESD diode to VCC and then GND and so influencing the measurement.

 

[erikl]

You could use a second protection diode (self-polarizing its extra n-well) in series with the ESD diode to VCC. 2 diodes in series shouldn't disturb the measurement any longer.

 

[ESDSolutions]

Or you can use an alternative ESD protection approach: Take out the diode between IO and Vcc (which is causing the problem) and replace it with a local protection clamp between IO and Vss. You could just use the same cell as the powerclamp if the dual-diode + powerclamp is effective (ESD protection) in the current IC implementation. The diode between Vss and IO can stay.

This approach is used for other IO's like 'hot-swap', 'overvoltage tolerant' or many other names where the IO signal voltage can be higher than the Vcc voltage level.

Hope this works!

ES