Original question:
Hi,
I have a question about Standby Mode.
If "t > tINACTIVE" and " EN = nSTB = high & VIO > UVIO" become true at the same time, which mode is next?
--2022.10.18 add--
I would like to confirm that "nSBT is always low immediately after transitioning from Standby Mode to Sleep Mode".
If nSTB=H immediately after transitioning from Standby Mode to Sleep Mode, a special operation of setting nSTB=L once and then setting nSTB=H again is required to transition to another Mode.
Hello,
When it comes down to it nothing can truly happen simultaneously. So let me break down what will happen based on which even happens first. Firstly, let's say that you pull up EN and nSTB right before the SWE timer times out. Then you would transition to normal mode just as expected.
Next, let's say that the SWE timer times out before you are able to transition your EN and nSTBY pins high. What happens when the SWE timer times out is it clocks the state of your EN and nSTB pins. It would see that they are both low. So in order to transition out of sleep mode into normal mode the device would need to see a transition of nSTBY from low to high while EN is high. What you should do is you should first pull nSTBY high and then pull EN high. The reason for this is because, only after entering sleep mode with the SWE timer, the device uses the edge on EN to clock the nSTBY pin. So you want to clock the nSTBY pin while it is already high. If you pull EN high first then it will clock the nSTB pin as low and then you would need to pull nSTBY high and send another edge on EN in order to clock that the nSTB pin is high. Then you would need another edge on EN to bring it back high so that you enter normal mode.
We actually describe this behavior in our TCAN1463 datasheet and we are in the process of updating the TCAN1043A datasheet to include this explanation as well.
I highly recommend reading section 9.4 of the TCAN1463 datasheet to understand how this works.
The big takeaway here is that you should always transition your nSTBY high and then your EN high.
Let me know if you have any more questions.
Best,
Chris
But I don't understand "the device uses the edge on EN to clock the nSTBY pin" you mentioned. I think the edge of EN isn't needed, right?
Normally yes this is correct, but when you enter sleep mode due to a SWE timer (that is the t_inactive timer) there are extra conditions in order to leave sleep mode. Here is the snippet from the TCAN1463 datasheet. Like I said we are in the process of adding this to our TCAN1043A datasheet.
So what this is essentially try to say is you need a transition on the EN pin (low to high or high to low) in order for the device to read the state of the nSTBY pin and then transition you out of sleep mode. You are correct that if you enter sleep mode without the SWE timer then you do not need an edge on the EN pin.
Also, in the case of TCAN1043A, the level of EN is reversed when nSTB toggles, right?
I'm not really sure what this means can you elaborate? There is nothing in this device that would reverse the logic level of another pin.
Best,
Chris
>>Also, in the case of TCAN1043A, the level of EN is reversed when nSTB toggles, right?
>I'm not really sure what this means can you elaborate? There is nothing in this device that would reverse the logic level of another pin.
⇒
According to the datasheet of TCAN1043A,
- the transition condition from Sleep Mode to Silent Mode is "EN=low, nSTB=low to high"
- the transition condition from Sleep Mode to Normal Mode is "EN=high, nSTB=low to high".
On the other hand,
according to the figure of TCAN1463,
- the transition condition from Sleep Mode to Silent Mode is "EN=high, nSTB=low to high"
- the transition condition from Sleep Mode to Normal Mode is "EN=low, nSTB=low to high".
The EN levels are inverted between TCAN1043A and TCAN1463.
Best,
Ito
Not exactly,
What you'll notice is what takes it to normal mode is when the EN goes back to high:
Once the device sees the that the nSTB pin is high, then it will look to the next edge of the EN pin to know what state to transition to. In both cases the logic for the EN pin stays the same.
Best,
Chris
