BQ76PL455A: VP1, VDIG and NPN transistor (Q17) not working

Hi Vikram,

Are you using the GUI, and can you communicate to the bottom board?

Please check that both actuators of SW2 are set to "SINGLE" for the board connected to the MCU/PC and set to "DIFF" for the top board.

Can you check that the cable is connected to J5 (DIFF COMM HIGH) on the bottom board and J4 (DIFF COMM LOW) for the top board?

I would also advise double checking that COMMH+ of the bottom board is connected to COMML+ of the top board, and COMMH- to COMML-. You can use the continuity or ohmmeter functions on a DMM for this.

Can you also measure the voltages on S0, S1, S2.... S16 for me please? On both boards, I just want to be sure.

Hi Vikram,.

You are welcome...

So you are testing two boards individually, and one of the boards does not wake up?

Are you testing with a PC? I would put a scope on WAKEUP, RX, TX and watch for activity.

Could you also measure the voltage across R52 and R54 (the two 200 ohm resistors in series with the VP regulator) when you try to wake up the part?

I am curious about what you would see if you scope the supplies (VP, 5VAO, Vref, etc) while trying to wake up.

Have you tried any modifications to the board, or have you plugged in cells recently? I am wondering if the IC has been damaged. You may consider checking continuity at the pins and look for shorts as well.

Yes testing them individually to start with. I have not modified the board at all. Have both options Using TMS570LS04x launchpad with BQ EVM and with PC.
Both the resistors seems to be measuring 0V's. The VP Vref are both 0V and V5VAO is at 4.49V.
When i try to connect it with the PC the gui responds with cannot open the port. I have also replaced the IC today. Have doe that and in same situation again.

Vikram,

Thank you for the info.

Can you try to watch the wakeup signal on the board? I would be concerned with U2, C67, and C45. If these devices are damaged the wakeup signal will not get through, as well.

C67 measures 5.16V and C45 measures 0V, the output of U2 VCC measures 5.16 and Wakeup is down to 0 ?

you mean the C45 is shorted to ground ?

It seems to make the noise so does that mean the CAP is shorted to ground ?

Hi Vikram,

That seems to be the case! Try replacing it with a 0.1uF cap. If you don't have one on-hand, the board should still be functional without it, i think... that would at least get you up and running

Thank you so much David thats been great help thanks a lot. Can we be in touch ?

You are welcome!

If you have any pl455 related questions, you can always post on the forum. It is helpful, as it builds somewhat of a "database" for others to find. I try to respond to pl455 related questions withing 24-48 hours, but sometimes fall behind depending on workload

If you have material that you are uncomfortable sharing you can reach out to d-wiest@ti.com

Hi David,

I have now sorted out all issues with the board and now want to use two BQ EVM's for series communication (i only want to test the software for communication working) do i need to get any hardware changes on top BQ EVM in stack to get both of them working as daisy chain and communicate ?

I have not even series'd the cell connections from bottom board to top board. Do i need to do any changes also ?

All i have done now is connected the J5 of bottom device to J4 of top device for daisy chain communication and 2 nobs on SW2 is set to direct towards diff side.

Am i missing something ?



Kind Regards

Vikram Jain

Hi Vikram,

Glad you are making progress.

I would recommend double checking the wiring conenctions of your daisy chain cable, just for good measure.

Those should be the only hardware changes you need for the EVM.

FYI, when we do most of our testing we use a resistor ladder consisting of 16 100ohm resistors in series and a power supply to emulate the cell voltage drops. This lets us do most of the testing without live cells.

Since the communications are AC coupled, you could use two boards stacked to measure just a 16 cell stack (or R ladder). This will let you keep the voltage to a minimum (64V vs 128V) while testing if you are interested. Just a couple things to think about.

Once you stack the cells in series, just remember that the GND of the top board will be at the same voltage as TOP of the bottom board, since they are stacked.

i have cross checked all the diff comms connections and they seems to be okay ? What else could be wrong ? any hardware issues that i can look for ? So J5 Pin 1 to 4 are connected to J4 pins 4 to 1 on top device

Vikram,

Do both boards wake up when you send the wakeup pulse?

How do the supply/cell voltages measure for the top board (and the bottom board if it isn't working)

Hi David,

I am current using it BQ GUI and not micro controller. Both the boards are connected to individual cells stacks and cell 15+ve of bottom stack is connected to cell 1 -ve of top stack for series connection.

When you open the GUI and connect the serial connector the LED on bottom board lits up and the top board doesn't. But i have checked individual boards connecting with the Gui and both of them work okay.

Also when the diff comm is connected only the bottom boards wakes up and not the top and the GUI confirm only 1 board in the network

Just to make sure...

On the bottom board, you switched both actuators of SW2 back to Single?

Yes and on the top there are towards diff