TJA1043 state after power-on

[nexy_sm]

Hi all,

I am using TJA1043 in my project, and the issue I am experiencing is the following:

On power-on, only Vbat is present, despite that, in the first moment, INH signal is set high and only after about 200ms it is set floating.

My question is why TJA1043 does not immediately go to sleep-mode after power-on when only Vbat is present? How can I force it to do that?

Our setup is pretty simple, and the circuit is identical to the one provided in the application note.

[reyes]

Hi,

The only way to put the TJA1043 into Sleep Mode is via Go-to-Sleep mode, and with an under-voltage detection on either VCC or VIO:

1. Using the Go-to-Sleep Mode (STBN to LOW, EN to HIGH).

If it is selected for longer than the minimum hold time of go-to-sleep command th(min) (20 us), the transceiver is automatically forced into Sleep Mode switching the pin INH to floating.

2. By an under-voltage detection on VIO or VCC.

When the under-voltage detection time (350ms) on either VCC (Vuvd(VCC) = 3.5V) or VIO (Vuvd(VIO) = 1.8V) elapses before the relevant voltage level has recovered.

Have a great day,
Jose

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[nexy_sm]

Hi,

in my use case, when I switch the board on, only Vbat is present. What I measure is that INH is active for 200ms after which it goes floating, and I assumed that TJA1043 is in one of the states, and in parallel it measures the absence of the supply voltage.

Is there any chance to send it directly to the sleep-mode, before it actually starts with measuring 350ms until UVnom flag is set? Since this can be done only by STB_N and EN pins, I wonder which condition has priority, undervoltag or pins?

Thanx

[reyes · Accepted solution]

Hi,

No, if you are using under voltage to go to sleep mode, the 350ms time window with undervoltage condition should pass before going to sleep mode.

Using the Go-to-Sleep Mode (STBN to LOW, EN to HIGH pins), first, the device should be in functional mode.

Have a great day,
Jose

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[nexy_sm]

Thank you very much