BQ76PL455A-Q1: Incorrect value of V5VAO

MOHIT KUMAR GUPTA

Part Number: BQ76PL455A-Q1

I have made our own evaluation module for this IC and I'm facing the following issue:
I have 2 signals named VIO-REG and VIO. VIO-REG is generated from emitter of transistor and VIO is the main signal to the chip which powers the RX/Tx and fault_n pins. Now before these two signals are joined , I'm getting correct values of V5VAO, VDIG,NPN_BASE. But the moment I connect VIO and VIO-REG, the V5VAO drops to 3.9V and there is a constant noise which comes from the board.
So why is this happening?

over 5 years ago

0 Andy Li55 over 5 years ago

TI__Intellectual 2520 points

Hello user,

Since you connect RX/TX of 455 to MCU, then VIO should be powered by MCU's power supply.

Is there a digital isolator between MCU's UART and 455's UART? please provide detailed block diagram of your system.

See pin description as below.

Thanks!

Andy

0 MOHIT KUMAR GUPTA over 5 years ago in reply to Andy Li55

Prodigy 100 points

Actually the microcontroller se are using is Nucleof103rb. Also we have tried the communication without connecting VIO and VIO-REG, but in that case IC doesn't communicates.

Also we have 4 other boards ready and we are doing the same( connecting the two signals ) and it's working perfectly fine.