open-source-silicon.dev

Is there a maximum voltage that the caravan analog io pads can take? I have an analog pad connected to just metal with no circuit components that I want to apply a bias voltage to on the order of a 100V or more

<@U02NGKNUN5V> there are bare metal analog pads on the top of the Caravan harness.

<@U02NGKNUN5V>:  Be aware that the Sky130 process does not have any devices that will tolerate 100V.  That said, I used to play around with floating gate circuits on, I think, a 0.5um process (quite some years ago now) and assuming that required biasing the programming gate to somewhere between 50 and 100V.  So assuming you know what you're doing and you're not exceeding dielectric breakdown then yes, you can get a high voltage through the Caravan pads at the top, because they are not connected to any ESD protection circuitry and so there are no connected devices to break down.  Note that by doing so you inevitably create an antenna, so keep the connection to the pad as short as you can make it.

Thank you for the information. We are interested only in applying a bias voltage a large mesh structure in m5 for the purposes of external charge sensing

image.png

If you're curious, full context is that we have this charge-sensing pixel array through the exposed m5 on the pixels, the pale-blue mesh structure is the pixel guard ring and we want to bias it in order to drift more charge onto our exposed metal

That seems like a perfectly reasonable application for a 100V input.