Comments on Does preventing CMOS latchup with a diode in VCC path prevents protection diodes from working?
Post
Does preventing CMOS latchup with a diode in VCC path prevents protection diodes from working?
I want to use ADG726 multiplexer for an application where the multiplexer inputs could have potential on them before ADG726 is powered up. Seeing that ADG726 is a CMOS device, it seems it might be susceptible to latchup. One way to prevent it according to theory is to put a diode in series with the power rail, blocking current path when the device is powered off:
However, doesn't doing this also void input protection when the device is powered on? Looking at Absolute Maximum Ratings table it looks like the digital and analog inputs are clamped:
If the inputs exceed the VCC by the forward voltage of the input protection diode, the current cannot flow into the VCC rail due to the series diode. Is this indeed the case, and what better ways are there to protect against latchup while still maintaining input protection?
1 comment thread