A problem about TJA1021 from power-on mode go to normal mode

[Woody1]

Hello;

        I have a problem about TJA1021 in electrical properties test.

First:  The MCU set the SLP to low before go to sleep .

Second: Vbat come down from 9V to 1V.

Third: Vbat turn back from 1V to 9V.

       After these step MCU cant wake up from sleep mode. I found that TJA1021 didt translate the

singalfrom LINBUS to RXD. So MCU cant wake up by LIN singal.

      Because of TJA1021 go to reset is faster then MCU. When the Vbat come down and turn back TJA1021 has been reset but MCU didnt reset yet by some capacitance.  The SLP always keep LOW states. At that time TJA1021 is in power-on mode and RXD is floating.

     How can I slove this preblem? please give me some suggests.

Thanks.

[guoweisun]

If VBAT drops below Vth(VBATL)L, a protection circuit disables the output driver. The driver is
enabled again when VBAT > Vth(VBATL)H and a recessive level is present at pin TXD.