BQ40Z50-R2: BQ40Z50-R2 – SMBus Communication Failure and No Output Voltage on PACK+, CHG, and DSG Pins

Sumedh Saptarshi

Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQSTUDIO, BQ40Z50, EV2400

Tool/software:

We are currently developing a Battery Management System (BMS) using the BQ40Z50-R2 IC, with SMBus communication for interfacing with BQStudio. The battery pack configuration is 14.8 V, 6600 mAh (4S3P).

We are facing an issue where SMBus communication is unable to establish a connection with BQStudio. The attached screenshot shows the error message encountered.

During PCB-level diagnostics, the following measurements were recorded:

-Voltage between PACK+ and GND: 0 V (expected: ~14–16 V).

-Voltage at CHG (Pin 31) and DSG (Pin 28): 0 V (expected: ~25.95 V).

-Voltage across R20 and at Q3: 0 V (expected: ~14.48 V).

For reference, the schematic is attached.

2046.0043-08-7081 sch.pdf

2 months ago

0 Alan Frias 2 months ago

TI__Mastermind 29245 points

Hello,

This question has been assigned and will be reviewed when possible.

Thank you,
Alan

0 Sumedh Saptarshi 2 months ago in reply to Alan Frias

Prodigy 90 points

Hello Alan,

This is our urgent issue can you please help on this as soon as possible.

0 Sumedh Saptarshi 2 months ago in reply to Alan Frias

Prodigy 90 points

Hello Alan, I would appreciate your assistance in resolving this issue.

0 Miguel Castro Gonzalez 1 month ago

TI__Intellectual 2472 points

Hello Sumedh,

Sorry for delay in response. In order to wake up the gauge, you need to connect a charger or force some voltage on the PACK+ pin.

After this, the device will start powering from BAT pin, and you should be able to communicate.

-Miguel

0 Sumedh Saptarshi 1 month ago in reply to Miguel Castro Gonzalez

Prodigy 90 points

Hello Miguel,

I am following the same procedure but still the problem is there, bq40z50 not able to communicate.
Please help it is very urgent issue.

To wake up we are shorting the PACK+ and 4P so it will wake up.

0 Miguel Castro Gonzalez 1 month ago in reply to Sumedh Saptarshi

TI__Intellectual 2472 points

Hello Sumeth,

I understand. Sometimes BQStudio doesn't acknowledge the host right away, and I try to open it again, and seems to work.

Can connect scope on thermisistor (TSx) pin and see if there is any pulses? Pulses will indicate the FW is running and the part is power up.

Are your pullups on the SMBus on your host side? I didn't see any in your schematic

-Miguel

0 Sumedh Saptarshi 1 month ago in reply to Miguel Castro Gonzalez

Prodigy 90 points

Hello Miguel,

1.Host side means do you mean to say EV2400 board?

like this below image?

2.Will check thermistor on the scope

3.We used below circuit for the design here there are no pull ups
2. tidrjp4.pdf

0 Miguel Castro Gonzalez 1 month ago in reply to Sumedh Saptarshi

TI__Intellectual 2472 points

Yes, I meant the EV2400 board.

You should have some voltage on the PACK. Have you tried to force voltage on the PACK+ with a power supply to check?

-Miguel

Power management

Power management forum

BQ40Z50-R2: BQ40Z50-R2 – SMBus Communication Failure and No Output Voltage on PACK+, CHG, and DSG Pins