I am trying to make a simple Schmitt trigger circuit with the TLV9302. Input voltage is 5V. On the non-inverting input, I have a voltage divider from the 5V supply using two 10k resistors, with a 1M hysteresis resistor. The inverting input has a signal that measures a temperature using a 1k thermistor. The unused op-amp in the dual package is set up as a voltage follower with the non-inverting input connected to GND.
According to simulations and calculations, this should give a window of ~25mV centered at 2.5V. However, the midpoint reads ~2.4V. This does not seem like a huge difference, but 100mV will make a difference in my application.
I removed the hysteresis resistor, and just measured the voltage of the divider. The top resistor (VDD5 to input pin) reads 2.6V, the bottom resistor (input pin to GND) reads 2.4V. I confirmed the divider resistors are a solid 10k by removing them from the board, and also using brand new resistors for a second attempt (they are 0.1% tolerance, so I am not surprised they read properly)
There are no other connections to the node, except the non-inverting input of the op-amp. By my calculations, this means that ~20uA is apparently flowing into the non-inverting input of the op-amp??
As far as I can tell, the board is free of shorts. The op-amp inputs are not clamped to each other internally (one reason I chose this part). I'm a bit at a loss of what's going on here. The only thing I can think of at this point (the last bastion of a troubled designer) is the op-amp is damaged somehow; I may try replacing it.
Anyone have any ideas?? Thanks!
Edit: here's a screenshot of the PCB design in Altium. The standard trace thickness is 25 mils. I ordered boards from OSH Park. C2 and C3 are not populated (I removed them from the schematic screenshot for clarity), they were included for potential noise filtering.
