TS3A27518E: Eliminate false ON of NC, NO, and COM when starting up the power supply (Vcc)

Hello Shinichi,

1. We do not recommend using the device within its absolute maximum ratings. This can cause damage to the device. 

The TS3A27518E has the power-down feature that whenever the device is off all of the switch paths are in high impedance mode. So when the supply is off the is no signal passing through the device and no damage will be caused.

2. So according to the graph you mentioned (as seen below) with Vcc = 1.65V at ~0.6V the IN pin is going to toggle high and we will see an output signal, which in this case is 1.65V. 

While the 0.6V might seem as the threshold for the control pin to toggle the switch, I believe it is in the unknown region of VIH and VIL. We have an FAQ about it explaining what is that unknown region and what does it mean, but I will also explain below. 

In the example shown below the case is with Vcc = 1.8V. The red region is that unknown region I mentioned earlier, which means while the IN pin is in that voltage range. The switch behavior is not predictable. So when we spec VIH and VIL we provide some breathing room to guarantee device behavior. As shown in the capture below the VIH can be at 1.17V, but we can't really guarantee that every device in that case will toggle high so there is extra breathing room provided and the VIH will be specked at 1.35V instead to guarantee device behavior. Same idea with the VIL case, but the opposite. 

This whole explanation was for to basically say that while 0.6V does toggle the device on, it is not a guarantee and probably ~0.85V is where the actual VIH spec is.  

So to your question, the device is enable low, so if there is a 1.2V signal on the EN pin then NC, NO, or COM will not turn ON. 

Your understanding is correct. 

Thanks,

Nir

Hello Shinichi,

There seems to be a slight misunderstanding. The power down feature makes all switches paths to be in high impedance mode when Vcc = 0V, not when its sets to some voltage. 

For clarification, can you please elaborate on what will the voltage level on the input of the device before the supply voltage settles? At least an estimate?

From my understanding you will have a voltage input on the mux greater than the supply, because the voltage on the supply won't settle fast enough to match the input voltage; which might cause a false on. If that is the case then I can recommend the TMUX2889. It can pass signals greater than its supply up to 5.5V. 

Thanks,

Nir 

Hello Shinichi,

In general we don't recommend using our devices under absolute maximum conditions. But as you mentioned: "When the absolute maximum rating is specified as a voltage, the device should not be damaged even if the power is turned off." - you are correct because of the power-down feature the device has.

Signals can be inputted to the device while its turned off without the risk of damaging it, since the switch paths go into high-impedance state. 

Thanks,

Nir 

Hello Shinichi,

Power-down mode is activated when Vcc = 0. If Vcc > 0, then the device is not in power-down mode anymore and the device is not in high impedance. I want to clarify that and make sure there is an understanding. 

The TS3A27518E is an enable low device, meaning in order to enable the switch a signal of 0V (low) needs to be sent to the enable pin. NC, NO, and COM will not be on if a positive voltage signal is sent to the EN pin. 

IN1 and IN2 have different logic though.

Thanks,

Nir 

Hello Shinichi,

We can't guarantee device behavior outside of the recommended voltage range.

Area 3 in question is in the range outside of the recommended operation spec. I can't provide solid answers since the device behavior is unpredictable at that voltage range. 

1. The device might turn on below the recommended range, this is something that we can't predict.

2. This might happen, but again we can't guarantee device behavior outside the recommended operating range. 

3. Again, this might occur but we can't predict it.

Thanks,

Nir