BQ76952: Schematic check request

Statham Su

Genius 4990 points

Part Number: BQ76952

Hello Sir:

Please help to check our schematic.

Our battery pack is using 13s type.

We don't need to drive MOSFET, just used the DCHG and DDSG signal for our MCU detected status.

DTF01_2nd Protected_V04.pdf

The other does BQ76952 has functional safety manual or other UL certification?

If yes, can you share it for us?

Looking forward your feedback.

Thanks a lot.

over 2 years ago

0 Andria McIntyre over 2 years ago

TI__Expert 8526 points

Hi Statham,

Here are a few notes on the schematic:

I am assuming that the 0Ohm NC resistors are for the purpose of shorting unused cell inputs. If this is the case, please refer to this FAQ for notes on which cell connects should/ should not be shorted: [FAQ] BQ76952: Connecting battery cells to the BQ769x2 family of monitors - Power management forum - Power management - TI E2E support forums.
C138 should be 22nF
Depending on the pack voltage and current drive of the REG pins, the power dissipation on R355 will vary. I recommend ensuring that this resistor will be able to dissipate enough power for your system. You may need multiple resistors.
It is recommended to connect a 10MOhm resistor from BREG to VSS.
C141 should be removed, but C17 should stay.
I recommend using a 1uF capacitor for C20 to maintain BAT pin voltage level and a 100pF capacitor for C18 to filter noise.
Since you are not controlling any high-side NFETs with the BQ76952, you can remove C24 and leave the CP1 pin connected directly to BAT. If you remove C24, please disable the charge pump in the register settings.
If you want to enter SHUTDOWN mode, then please do not connect a resistor to the TS2 pin. If the TS2 pin is pulled down, then the device will never enter SHUTDOWN mode.
If you are not controlling protection FETs with the BQ76952, then the CHG and DSG pins should be left unconnected.
In typical applications, the LD pin should have at least 10kOhm resistance connected in series, but if you are not using CHG and DSG FET control, then the LD pin can also be connected to VSS.
If i2c communication is used, the SDA and SCL pins should be connected with pull-up resistors.

We have an FMEDA for the BQ76952 covered under NDA. I will notify someone to reach out to you regarding that information.

Best,

Andria

0 Statham Su over 2 years ago in reply to Andria McIntyre

Genius 4990 points

Hi Andria:

Please refer our feedback as below and we also updated our schematic, please kindly help to check again.

Andria McIntyre said:
I am assuming that the 0Ohm NC resistors are for the purpose of shorting unused cell inputs. If this is the case, please refer to this FAQ for notes on which cell connects should/ should not be shorted: [FAQ] BQ76952: Connecting battery cells to the BQ769x2 family of monitors - Power management forum - Power management - TI E2E support forums.

Yes, we followed it, and in our application, we want to short VC15 to VC14 and VC9 to VC8 by using R31.

Andria McIntyre said:
C138 should be 22nF

OK, I will let it within 15 to 27nF.

Andria McIntyre said:
Depending on the pack voltage and current drive of the REG pins, the power dissipation on R355 will vary. I recommend ensuring that this resistor will be able to dissipate enough power for your system. You may need multiple resistors.

It is recommended to connect a 10MOhm resistor from BREG to VSS.

OK, we will change to 10Mohm.

Andria McIntyre said:
C141 should be removed, but C17 should stay.

Ok, we will change C17 and C16 to 1uF, and removed C15.

Andria McIntyre said:
I recommend using a 1uF capacitor for C20 to maintain BAT pin voltage level and a 100pF capacitor for C18 to filter noise.

Since you are not controlling any high-side NFETs with the BQ76952, you can remove C24 and leave the CP1 pin connected directly to BAT. If you remove C24, please disable the charge pump in the register settings.

OK, we will follow your recommendations, C18 use 100pF, removed C24 and let CP1 (pin46) connect to BAT (pin47)

Andria McIntyre said:
If you want to enter SHUTDOWN mode, then please do not connect a resistor to the TS2 pin. If the TS2 pin is pulled down, then the device will never enter SHUTDOWN mode.

This 76952 are using on standalone mode, if so, can you let me know what should we do on TS2?

Andria McIntyre said:
If you are not controlling protection FETs with the BQ76952, then the CHG and DSG pins should be left unconnected.

In typical applications, the LD pin should have at least 10kOhm resistance connected in series, but if you are not using CHG and DSG FET control, then the LD pin can also be connected to VSS.

We will connect to test points on CHG/DSG pins, and reserve the LD functions.

Andria McIntyre said:
If i2c communication is used, the SDA and SCL pins should be connected with pull-up resistors.

OK, we will do it on MCU board.

Andria McIntyre said:
We have an FMEDA for the BQ76952 covered under NDA. I will notify someone to reach out to you regarding that information.

Please help to send the e-mail for me. statham.su@arrow.com

Thanks a lot.

+1 Andria McIntyre over 2 years ago in reply to Statham Su

TI__Expert 8526 points

Hi Statham,

In response to your edits:

Statham Su said:
Ok, we will change C17 and C16 to 1uF, and removed C15.

Please do not change the C17 and C16 values. Please do not remove C15. Remove C141.

Statham Su said:
This 76952 are using on standalone mode, if so, can you let me know what should we do on TS2?

SHUTDOWN mode can be used when the BQ76952 is standalone or used with an MCU, so this information does not tell me if you will use this mode or not. Configure TS2 pin according to whether you will use SHUTDOWN mode or not. If yes: TS2 pin should not be pulled down at all times. If no: TS2 pin can be connected however you would like.

Best,

Andria