BQ40Z50-R1: VCC 100 Ohm Resistor - Can this be increased to 150 Ohms

Joseph DeWitt

Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQ40Z50

Hi,

In regards to the 100 Ohm resistor that is connected to the VCC pin of Texas Instrument BQ40Z50-R1, can this resistor be increase to 150 Ohms without negatively impacting the performance of the IC?

Best regards,

Joe DeWitt

over 2 years ago

0 Wyatt Keller over 2 years ago

TI__Guru** 105770 points

Hello Joe,

This depends on the number of series cells, with 1S application I would not recommend increasing the series VCC resistor to 150Ohm due to the voltage drop that could occur across this pin during flash write/erase which is maximum 15mA, which could cause the gauge to brownout. 2S and above it would be very unlikely to have a brownout due to the high voltages.

Sincerely,

Wyatt Keller

0 Joseph DeWitt over 2 years ago in reply to Wyatt Keller

Intellectual 320 points

Hi Wyatt,

I hope you're doing well.

The application will involve three 3.6 nominal voltage cells in series. Also attached is a screenshot of the resistor (R9) that is connected to the VCC pin that I am referring to in the BQ40Z50 BMS circuit which I am hoping can be increased to 150 ohms from 100 ohms for confirmation purposes.

Best regards,

Joe DeWitt

+1 Wyatt Keller over 2 years ago in reply to Joseph DeWitt

TI__Guru** 105770 points

Hello Joe,

With a 3s battery design I don't think you should have any issues increasing the VCC resistor from 100ohm to 150ohm.

Sincerely,

Wyatt Keller

0 Joseph DeWitt over 2 years ago in reply to Wyatt Keller

Intellectual 320 points

Wonderful, thanks so much for the help as always Wyatt. Much appreciated.

Best regards,

Joe DeWitt

0 Joseph DeWitt over 2 years ago in reply to Wyatt Keller

Intellectual 320 points

Hi Wyatt,

Quick follow up question. Seems like 200 Ohms resistors are in greater supply for the power rating I'm looking for. Would a 200 Ohm resistor also be acceptable for this purpose (R9 in the image below upstream of the VCC pin)?

Thanks in advance for you guidance.

Best regards,

Joe DeWitt

+1 Wyatt Keller over 2 years ago in reply to Joseph DeWitt

TI__Guru** 105770 points

Hello Joe,

Under worst case of 15mA with 200Ohm would be ~3V drop. With a 3s system your min voltage is probably around 9V, so the gauge would be at 6V which is above the operational voltage.

Sincerely,

Wyatt Keller

0 Joseph DeWitt over 2 years ago in reply to Wyatt Keller

Intellectual 320 points

Hi Wyatt,

Wonderful.

Thank you for the feedback and electrical design explanation as well. Super helpful and insightful as always.

Best regards,

Joe DeWitt

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BQ40Z50-R1: VCC 100 Ohm Resistor - Can this be increased to 150 Ohms