We are using your TS512 with (+/-15V rails) as a low current (1mA), 10V voltage follower.
We have a test case where the output the TS512 is pulled to a 19V/100mA source for just 600us, and I am trying to assess whether this transient could internally damage Q29 or Q30 or anything else in the o amp (referring to TS512 schematics from datasheet, see also below).
My understanding is that during such transient the negative feedback would try to pull the output down to -15V to counter back that transient, hence Q29 would be cut-off and R13 would prevent the B-E junction from breakdown. On the other hand Q30, I think it would be almost fully "on", which would potentially create a differential voltage across R14 of 19-(-15)=34V. The question is:
1. Would the output still limit to 25mA so would R14 be safe -and by extension TS512- during those 600us)?
2. Is there any other considerations to take into account to assess the robustness of this part under this transitory?
NOTE: This question and answer originated from a customer support case which was handled by us. We regularly review support cases and add any helpful ones here for all to benefit from.
1 ACCEPTED SOLUTION
Accepted Solutions
In this case the current will not go through transistors but through internal ESD protection diodes which has current limitation about 10mA. The only way how to reduce this current is to increase output impedance to roughly 400Ohm.
You can take the feedback behind this impedance and use one additional resistor to protect the input as well, see below. In this case your functionality should not be affected.
In cases when overvoltage is too high so that op amp is not able to keep its output below Vcc (Injected current is too big) you may increase output impedance or consider adding Schottky diode from output to Vcc as shown below.
By the way, similar approach is applicable to most ST op amps.
In this case the current will not go through transistors but through internal ESD protection diodes which has current limitation about 10mA. The only way how to reduce this current is to increase output impedance to roughly 400Ohm.
You can take the feedback behind this impedance and use one additional resistor to protect the input as well, see below. In this case your functionality should not be affected.
In cases when overvoltage is too high so that op amp is not able to keep its output below Vcc (Injected current is too big) you may increase output impedance or consider adding Schottky diode from output to Vcc as shown below.
By the way, similar approach is applicable to most ST op amps.
