I am connecting TMUX1108 to electrochemical input of AD5941.AD5941 has only three GPIO pins.These GPIO lines will be connected to address lines of the MUX.No pin is available with AD5941 to control the EN pin of the TMUX1108.All are working at 3.3V

My intention is during power on the MUX should be disabled.Initially I thought of connecting a pull down resistor and control the EN using GPIO,unfortunately I don't have enough GPIO's.Below is the block diagram of my circuit.


I need the mux needs to be enable after the power is stable.May I know can I connect an RC circuit to EN as shown below.
I want to define the ststes properly during power up.That is my intention.

 

That will work, however, given the presence of C1, R2 isn't needed. EN will be held off around 4mS depending on how fast the 3.3v rail rises.
C1 shouldn't be larger than necessary. When the power rail collapses C1 will discharge through R1 and also through the internal diode from EN to VCC, which is a much lower impedance than R1 and therefore can cause damage if the discharge current too great (normally ±10mA, though this device is spec'd at ±30mA) . 1uF is fine, with R1=10k and R2=inf.

 

I am connecting TMUX1108 to electrochemical input of AD5941.AD5941 has only three GPIO pins.These GPIO lines will be connected to address lines of the MUX.No pin is available with AD5941 to control the EN pin of the TMUX1108.All are working at 3.3V

My intention is during power on the MUX should be disabled.Initially I thought of connecting a pull down resistor and control the EN using GPIO,unfortunately I don't have enough GPIO's.Below is the block diagram of my circuit.

View attachment 357338
I need the mux needs to be enable after the power is stable.May I know can I connect an RC circuit to EN as shown below.
I want to define the ststes properly during power up.That is my intention.
View attachment 357339

Hi,

What I would do is first remove R2. Then, place that in series with the cap and TMUX chip. That puts some impedance between the cap and the IC chip EN pin. Without that, a TMUX protection diode could power everything for some time, which may not allow some things to shut down properly. Also, strictly speaking, in theory that diode could see a large current surge when the power is disconnected. The series resistor going to the EN pin will prevent that from being too high. A 1k resistor would limit the max current to less than 5ma during shutdown. This partly depends on the other loads on the Vcc buss also.

The other thing to think about is the timing between a turn on and turn off and then back on again. This would normally be long enough but to be sure you want the cap to discharge to low value like say 0.2v or lower before turning back on.