For TJA1080A, how to connect VBAT pin when not using it？

[boyajiang]

im using TJA1080a to design the flexray transceiver circuit without external battery supply, so how to connect VBAT pin when not using it？left open or connect it to VCC with capacitor？i can't find information for this application in the datasheet of TJA1080A, it only told me that VBAT should be powered at 6.5V~60V, but there is no external battery in my Flexray circuit.Also for the WAKE pin that is not used, should tie it to GND to keep the WAKE Flag be set all the time？

[guoweisun]

We suggest the VBAT = 6.5 V to 60 V with the undervoltage detection
voltage on pin VBAT is 4.5V.

[boyajiang]

thanks ,now it is clear for me that i can't floating the VBAT pin. I have used 3.3v and 5.0v supplies for TJA1080a in my TJA1080a system, the 3.3v supply is used for VIO pin and the 5.0v is used  for VCC and VBUF pins, so i wonder whether i can  directly connect the VBAT pin to the 3.3v or 5.0v supply with bypass capacitor instead external battery?  If the answer is yes, which one is better?3.3v or 5.0v?

[guoweisun]

Please get note that you can't floating the VBAT pin in your TJA1080 system.

Please connect TJA1080 VBAT pin without requirement level.

[boyajiang]

thanks, now it is clear for me that i can't floating the VBAT pin. I have used 3.3v and 5.0v supplies for TJA1080a in my TJA1080a system, the 3.3v supply is used for VIO pin and the 5.0v is used  for VCC and VBUF pins, so i wonder whether i can  directly connect the VBAT pin to the 3.3v or 5.0v supply with bypass capacitor instead external battery?  If the answer is yes, which one is better?3.3v or 5.0v?