BQ40Z50-R1: Fuel gauge and FET Operation

Sharif Kazwah

Prodigy 10 points

Part Number: BQ40Z50-R1

Hi there!

I have a couple of questions regarding the operation of the fuel gauge and the FETs.

1. Is the fuel gauge powered before or after the discharge of the FETs?

2. What is the FET bias when they are discharged and the cells are dead?

Essentially, I am using a battery (internal) that has this BMS and would like to connect an external battery on the same line as this battery (internal) and BMS, but I would like to understand how FETs behave once the cells are dead.

Kindest regards,

over 4 years ago

0 Wyatt Keller over 4 years ago

TI__Guru** 105590 points

Hello Sharif,

The FETs will be off when the gauge is in shutdown or the internal battery is dead and there's no external power.

The state of the FETs on the gauges wakeup depends on the firmware settings and safety settings.

Sincerely,

Wyatt Keller

0 Sharif Kazwah over 4 years ago in reply to Wyatt Keller

Prodigy 10 points

Hi Wyatt,

Thank you for your response! That clarifies a few things. So if I send a shutdown command and the FETs become disabled, is there a minimum voltage that the FETs need to fire back up? In other words, if I put my 12V on the same line of the battery, while it is "shutdown", will the battery wake up?

Kindest regards,

0 Wyatt Keller over 4 years ago in reply to Sharif Kazwah

TI__Guru** 105590 points

Hello Sharif,

Sorry for the late response.

You will need to apply a voltage on the PACK pin as defined in the Datasheet and TRM to wake the gauge up from shutdown.

Sincerely,

Wyatt Keller

0 Sharif Kazwah over 4 years ago in reply to Wyatt Keller

Prodigy 10 points

Got it. Appreciate the help!

Kindest regards,

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BQ40Z50-R1: Fuel gauge and FET Operation