Negative Inputs for CD74HCT4067-Q1

Hello Rajesh,

Bidirectional means that the device can be configured as a demultiplexer, having 16 inputs and 1 output, or as a multiplexer, having 1 input and 16 outputs.

As for your question about the device accepting negative voltages on the input, unless specified otherwise in the Absolute Maximum section, the inputs of logic devices are typically designed to operate only in the range of -0.5 V to VCC+0.5 V.

Could you please send us a block diagram of your design? We can better recommend a part or solution if we understand your application.

Also, I am moving this thread to the Automotive forum for additional support because the  CD74HCT4067-Q1 is an automotive-qualified part.

James

Hi James,

I need to selectively choose an AC signal (+/- 3V) for detecting its zero crossing point. I don’t mind if the output signal of MUX is distorted if input goes below -0.5V. I have a comparator connected to the output of the MUX to detct the crossing. Will I be able to use the MUX in this scenario? 

Or, can I connect -3.3V to the GND and 3.3V to VCC pins of the MUX and use with negative inputs?

Thank You

Rajesh,

I think you could connect -3.3V to the GND and 3.3V to VCC pins, but if you do that, you are operating near the Absolute Maximum voltage for the part. The Absolute Max is TI's guarantee that the part won't permenantly fail at those conditions. However, the Recommended Operating Conditions specified in the datasheet are the conditions at which the part will operate as expected. That would be between 4.5 V and 5.5 V (or +/- 2.25 to +/-2.75) for the CD74HCT4067-Q1.

Are you looking specifically for an automotive-qualified part? If so, I can leave your post in this forum for someone from the automotive team to respond. If you are not concerned with an automotive qualified part, I can move this to the Signal Switches forum to see if they have any suggestions.

In any case, if you could send a schematic or system block diagram, it would help us to provide an optimal solution. You can send this to me in a private message to me if you like.

James

Hi Rajesh, the apps engineer supporting this device is out this week. the recommended operation for input signal is 0V to VCC relative to GND. I did not support this device before and need to do bench evaluation for this specific application. The absolute max input voltage is 0.5V below GND. I' m not sure if the input has an ESD diode or not. Also 0.5V below ground on input may cause the device to latch up in case of single supply. Please give us until next week to give you an answer.