This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TIDA-010030: wake up circuit

Part Number: TIDA-010030
Other Parts Discussed in Thread: BQ76940

I tried to power up the board without installing the batteries. With pack+ 38V, I saw voltage on right side of C18 is 38-18=20V, but left side is 0v, meaning Cell13=0V. C1 is also 0v. After pressing S1, I didn't see TS1 rising edge trigger and thus no REGOUT. That I believe is due to C1=0V. 

Since I can't get REGOUT, I don't have 5V and no 3.3V that can power up MCU.

Question are

(1)why Cell13 is 0V? When batteries are not installed, should we see some voltage distributed among C13 to C1? Not all 0V? Is there any short circuit path from left side of C18 to GND? 

(2)Do we always need to install batteries or some resistors in order to power up the system?

(3)What is the initial PACK+ voltage you recommend to power up the board? 38V?

  • Hi, can anyone answer my questions? 

    I added 13 of 220 Ohm resistors to simulate 13 batteries. Result is still the same. I got Cell13=0V still.

  • Hi Eric, 

    It is necessary to install batteries to power on BQ76940 before adding voltage on PACK+ to wake up the system. As you mentioned, C1 is necessary to pull high TS1 and if no batteries or DC source on Cell13 or resister divider, C1 will be always 0V. Furthermore, BQ76940 require power to output REGOUT power, so you can try to install batteries or DC source + resister divider firstly and then install Pack+ to see if any improvement. Pack+ voltage should be >5V larger then Cell13 to make sure Q15 is on when installing Pack+.

    Thanks. 

  • Hi Ryan,

    Thanks for your info.

    So I can't just put resistors (220 Ohm) to replace batteries without DC source? If DC source is needed, how does connection look like? Which points are to connect DC VCC and GND?

  • Hi Eric,

    You are correct. Please connect your DC source between Cell13 to GND. 

    Please click "This resolved my issue" if no more questions.

    Thanks.

     

    Best Regards,

    Ryan Tan