MAX4945 might be the wrong choice for this design #1
Description
MAX4945 is an under/overvoltage lockout circuit used to protect the headstage. It turns on with the range 4.15 to 5.8V, which seems perfect. But there is an interesting issue that occurs when using a long and thin tether. Because of the series resistance of the tether, the voltage under no load needs to be quite high (e.g. like 7.5V). This way when the headstage starts to draw current and voltage is dropped on the tether, it settles at 5 or so volts at the headstage input. However, when using the MAX4945, 7.5V is too high for the headstage to ever turn on and we enter a deadlock. Choosing a version of this chip with a much wider range is probably a good idea (e.g. MAX4943 which has 7.4V overvoltage lockout) or it might just need to be bypassed. Alternatively, lower DC resistance tethers can be used (e.g. like the ones on the miniscope).