Can you tell me what behavior I should expect if pin 2 has an input voltage above VIH limits but the VCC to the part is not present yet. So for example, my input voltage on pin 2 is 1.2V but VCC is not powered on yet. Does the input latch to the input supply voltage?
Hi Cassidy,
In the case of Vin > Vcc (for example, Vin = 1.2V, Vcc = 0V), you just need to know if the input has a positive clamp diode. This information can be found in the Absolute Maximum Ratings table - although it requires some interpretation.
In this case, Vin (max) is 3.6V, which indicates that there is no diode. If it had said something like "Vcc + 0.5V" then that would indicate a positive clamp diode.
As for the behavior of the device with Vcc = 0 and Vin = 1.2V, that is described in the electrical characteristics table:
Ioff is the leakage current into any input or output pin when the supply is 0V and the input or output is any voltage up to 2.7V.
Note that this is only valid when Vcc = 0V. Since you said "VCC to the part is not present yet," I cannot be certain of the voltage on the Vcc pin.
