Issue: I'm noticing that when feeding a square wave to a 74VHC4020FT IC at a reasonable amplitude and frequency (amplitude: 0-3V or 0-5V, frequency: tried 1 kHz, 100 kHz, and 80 MHz) , the output from Q4 is not what I expect and strongly depends on the supply voltage. The Q4 output should divide the signal by 16, which occurs for a supply voltage between 2 V to ~3 V. Above this, there is a ~0.5 V window between ~3V and ~3.5V where the Q4 output divides by eight. Above ~3.5V the output is the supply voltage. I have tried this on several chips and measured the same behavior. Any advice would be welcome!
Manual: The chip should operate with a supply voltage (Vcc) between 2-5.5 V. The input voltage should be between 0-5.5 V (independent of the supply). The high level input voltage and low level input voltage depend on Vcc. For a Vcc of 2V, the high is above 1.5 V and the low below 0.5 V. For a Vcc between 3-5.5V, the high is above 0.7*Vcc and the low is below 0.3*Vcc.
Context: I grounded the CLR and GND pins, attached CK to a function generator, and Vcc to the power supply. The chip is soldered to a TSOOP-16 adapter and wires connect the ports to BNCs. The chip does not draw significant current.
Manual: The chip should operate with a supply voltage (Vcc) between 2-5.5 V. The input voltage should be between 0-5.5 V (independent of the supply). The high level input voltage and low level input voltage depend on Vcc. For a Vcc of 2V, the high is above 1.5 V and the low below 0.5 V. For a Vcc between 3-5.5V, the high is above 0.7*Vcc and the low is below 0.3*Vcc.
Context: I grounded the CLR and GND pins, attached CK to a function generator, and Vcc to the power supply. The chip is soldered to a TSOOP-16 adapter and wires connect the ports to BNCs. The chip does not draw significant current.