Hi,
Good Day.
For slow rise 3.3V VCC, 1st input is pulled down to GND, 2nd input is logic high. What will be the Output state when the VCC is rising to 3.3V? Can I expect the output to stay low as one of the inputs is held low when the supply is rising?
Please advise. Thank you very much.
Best Regards,
Ray Vincent
Hi Ray,
It depends on the configuration of your system. The output is not really "on" for the device until the supply is above 1.5V (ie there is not sufficient bias voltage for the output to operate). Once the device is on, then the output can drive significant current and force the node to a known voltage (typically GND or VCC). Only inside the recommended operating voltage range is the operation of the device guaranteed:
If, for example, your system had a pull-up resistor at the output, then I would expect the output to follow VCC until the logic gate turned on, after which it would be low.
The exact turn-on point can change from device to device and is not part of the specification we provide. For maximum system stability, I would recommend to assume that the output is "unknown" until the supply voltage passes 1.65V, after which it will be the expected high or low state, depending on the input voltages.
