Hi all, can anyone please tell me what is the estimated parasitic capacitance of a bond pad in caravan wrapper? I have a comparator circuit whose output current is only around 30nA and pulse width is 100us. Will it be able to charge the capacitor of pad? Should I put a buffer circuit with more current capacity? The issue is that I need to design a comparator with very low static current consumption but it should be able to drive 150 ohm ESD resistance and bond pad capacitance. Is there any solution for this issue, Or my concept regarding buffer and driver is not clear. Please help me with the issue. Thank you.

Considering your comparator has a digital signal output, you shouldn't be concerned about it. The digital IO pins are buffered. If you route its output to an analog pad, it won't work. But you must have some kind of load while simulating it. Try the technology smallest inverter logic gate.

Thank you so much for your answer @Luis Henrique Rodovalho. I have analog output therefore I need to put buffers in my circuit. Firstly I tried simulating my circuit with load of 150 ohms (ESD) and 1pF capacitor. I wanted to see the current through the capacitor load which is charging it but I got the following results. The current is zero and there is not much change in the output. How is load capacitor charging and discharging? I am just confused. Can you please have a look?

What you need is to measure the current from you buffers power supply and measure its RMS value. It seems to be very low, because you have peaks of current, and almost no current during the off state. That is a non issue.

@Luis Henrique Rodovalho I connected one more buffer in my circuit (Bigger W/L). I gave it a separate supply to calculate the RMS current. I used the following command

meas tran rms_cur RMS i(VDD2) from=0u to=230u

. The RMS current is 13.7u but I think it is because of high short circuit current of inverter. If I calculate the RMS current for period when output is high, it is zero. The output current is still zero when output is high. Why I can not see the capacitor charging current?

Hi Naina, I use a load capacitance of 10pf when I am modeling the capacitance an output bond pad. The ESD structure by itself is typically 4pf. For a typical PC board trace the capacitance is about 1pf for a for 2.5 cm of length of trace. If your output can drive a 10pf load, you should be good. Generally, I use the standard digital I/O circuitry that is in the standard cell library to drive the output bond pad. The standard cell library digital I/O circuitry should have the ESD structure built into the I/O output driver.

HI @Larry Harris, Thank you so much for your answer. Can you please point me to the sky130 i/o output driver? I am not able to find it.

I don't know the name of the I/O output driver. David Mitchell Bailey, please point Naina to the I/O output driver cell name.

Hi @Mitch Bailey Can you please point me to sky130 IO cell.

@naina singhal You can find the schematics for gpiov2 here.

Ok @Mitch Bailey. Sorry I thought there is a separate IO Cell present in library.

I would use 10pf.