BQ27520-G4: BQ27520YZFR-G4, temperature information for gauge algorithm

Vitali Lach

Part Number: BQ27520-G4
Other Parts Discussed in Thread: BQ25611

Hello,

I'm using a fuel gauge BQ27520YZFR-G4 in my design. Since we also have a TI charger BQ25611 with 4.7V REGN LDO voltage, we cannot use both on the same battery thermistor, because the voltage on his TS pin (resistor divider 4K12/16K9, up to 3,77V) would exceed the voltage range of fuel gauge (TS pin (Vadc1, TS, up to 2V).

My questions:

In the case the fuel gauge missing the temperature information, would it make the gauge algorithm imprecise?
The datasheet (page 10) says, the fuel gauge can alternatively receive temperature data from the host processor. Does it mean, we can write temperature information to the gauge fuel via I2C interface, and obtain the regular accuracy again?
In the charging process, the host processor may be powered off. I guess, the fuel gauge cannot get that information from the charger?

Best Regards

Vitali

over 3 years ago

0 Wyatt Keller over 3 years ago

TI__Guru** 102955 points

Hello Vitali,

Yes the temperature is very important for the gauging algorithm and can affect the SOC calculations.

Yes, you can program the temperature with the host, or you can use the internal temperature (of the gauge) if the battery temperatures are expected to be similar or the gauge is very close to the batteries.

No the gauge wouldn't be able to get the information from the charger without the host.

Sincerely,

Wyatt Keller

0 Vitali Lach over 3 years ago in reply to Wyatt Keller

Expert 1120 points

Hello Wyatt,

many thanks for that, that helps a lot.

OK, do you know how to make the charger BQBQ25611 and the fuel gauge BQ27520YZFR-G4 use a common NTC thermistor? In my understanding I need a kind of measuring transducer for NTC thermistor voltage.

Best Regars

Vitali

0 Wyatt Keller over 3 years ago in reply to Vitali Lach

TI__Guru** 102955 points

Hello Vitali,

We don't recommend using a shared thermistor, depending on the charger structure the two can interfere in the measurement or damage each other's TS pins.

Sincerely,

Wyatt Keller

0 Vitali Lach over 3 years ago in reply to Wyatt Keller

Expert 1120 points

Hello Wyatt,

thank you for that. Currently, we are considering an external NTC thermistor, that could be a simpel solution for us.

Best Regards

Vitali

0 Wyatt Keller over 3 years ago in reply to Vitali Lach

TI__Guru** 102955 points

Hello Vitali,

As long as the gauge gets accurate temperature data of the battery an external thermistor should be fine.

Sincerely,

Wyatt Keller

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BQ27520-G4: BQ27520YZFR-G4, temperature information for gauge algorithm