TMUX1219: Why tmux1219 does not work normally?

What exactly do you mean with "does not work normally"? Does it switch the wrong channel? Is the output voltage no the same as S1/S2?

What are the characteristics of SW.VEX.SEL?

Hi

Adding to what Clemen's asked, Could you also check what does the signal look like if you remove the mux  (U13) and short the signal path

Can you provide details on "often does not work" - What is the behavior you see when it does not work?

Can you take scope shots at inputs and output of the mux?

Are you using 5.5V supply for the mux?

Regards

Saminah

In some times, I can not switch S2 to D when SEL pin is high, it is always switch on S1 whether  SEL pin is high or low, and the D pin is always 2.5V. 

In other some times, the D pin is always 2.58V whether   SEL pin is high or low. 

SW.VEX.SEL is a GPIO from stm32 MCU, I measured the signal, it can be set to 0V or 3.3V according my intention.

When I remove U13 and short the signal path, the circui work normal. 

U13's power supply is 5.4V.

When I weld a new tmux1219 chip, it is work normal at once, it can switch to S1 or S2, and the D pin is 2.5V or 5V accordingly. But, after a period of time(for example one day or 5 days) it can not work normal and can not be recovered  again.

Hi,

Can you share the scope shots at input and output pin of U13 (both when working and non-working).

When you say "it can not work normal and can not be recovered  again" - what signal do you see at "D"?

Can you make sure you are following the design recommendations for the TMUX1219 as shown below:

Regards

Saminah

Indeed, the decoupling capacitors is not placed, and the weak pulld-own or pull-up resistor is not placed. But these can not damage the tmux1219 chip, only effect the stability.  Why many tmux1219 chip is gamaged?

Hi,

It is ok to not have the decoupling and pullup/pull down resistors on select pins buy you need to make the device is performing under recommended operating conditions

Can you confirm if your  supply to TMUX1219 is  5.4 V - the schematic shows VCC + A5V4

When the U13 is not working as required, can you probe VDD, GND and select pins of U13 as I mentioned earlier and share the scope shots - it could be the device is losing ground and you don't see it functioning after some time.

Regards

Saminah

When the U13 is damaged , I measured that VDD is 5.37V, GND is 0V，SEL is 0 or 3.3V. The GND pin is connected to AGND directly, it can not lose ground.