[FAQ] TMUX1308-Q1: EN and Control inputs termination - AM62P, AM62A use case

Hey Sreenivasa,

Am I understanding properly that the supply will ramp up first then the I/O's (Sx/D) will take a second or 2 to turn on? 
While the I/O's have some time to initialize to a known state, do we have the same restrictions on the control pin. Ideally I would tie the EN pin high to isolate the inputs/outputs of the device until the signals are ready.

Kallikuppa Sreenivasa said:

Are the TMUX tolerant to the inputs being open for some time during power cycle.

Which inputs are you referring to here?
The control inputs (Ax) are tolerant and can take up to 5.5V regardless of the supply voltage. 
Source and Drain inputs Sx and D are recommended to keep between GND and VDD but there are some protection features here that will allow you to exceed those values if you limit the current.

Thanks,
Rami

Hello Rami, 

Thank you for the inputs.

Kallikuppa Sreenivasa said:

Are the TMUX EN and address control inputs A0..2 tolerant to being open for some time ( 1..2 sec)  during power cycle until the SOC IOs are initialized.

I updated the question above,

Rami Mooti1 said:

Am I understanding properly that the supply will ramp up first then the I/O's (Sx/D) will take a second or 2 to turn on? 
While the I/O's have some time to initialize to a known state, do we have the same restrictions on the control pin. Ideally I would tie the EN pin high to isolate the inputs/outputs of the device until the signals are ready.

The SOC IOs controlling the Ax/EN will be in High impedance expected to take 1..2 seconds to be initialized to a known state. The TMUX inputs would be floating during this time.

Any thoughts please.

Regards,

Sreenivasa

Hello Rami, 

Thank you for the inputs.

Understand the recommendations.

In case the /EN is permanently enabled by hard wiring, do you have some recommendations on connecting the A0..A2 if the SOC takes 1..2 seconds to configure the address.

Regards,

Sreenivasa

Hello Rami, 

Thank you.

The TMUX output is typically connected to the ADC input.

Would it be Ok to connect a 100 nF cap directly at the output of the MUX. If not is there a recommended value.

The cap recommended on the supply ranges from 0.1 uF to 10 uF. Could you please guide on the recommended cap value and the rationale to choose the cap value.

Regards,

Sreenivasa

Hey Sreenivasa,

Yes, you can add a 100nF cap directly on the output of the mux. What is the purpose of the cap though?

The cap on the power supply is a decoupling cap that filters out noise on the power supply line. The values are selected so that higher frequency noise (kHz to MHz range) are filtered and your supply signal will be smooth.

Thanks,
Rami

Hello Rami, 

Thank you.

I do not have complete insight but looks like customer is measuring DC voltages and temperature inputs and might want to use the cap as the filter rather than RC.

Any thoughts please.

Regards,

Sreenivasa