BQ21040: BQ21040

Keith Haydon

Part Number: BQ21040

Hello TI team,

We are using the BQ21040 to charge a 2.6 Ah Li ion battery. We have two LED's connected to the CHG_N with a 1.5 K-ohm pull up resistor to both LED's. We've noticed if the battery is connected to the charger and the battery becomes over-temp (~45C) the red LED stops indicating charge and the green LED turns on indicating not charging as expected. BUT if the battery goes under-temp (~0C) while charging the red LED remains on. According to the datasheet section 8.4.5 TS

"Above 45°C or below 0°C the charge is disabled."

Why does the CHG_N pin not reflect both NTC faults (NTC Hot & NTC cold) ?

over 1 year ago

0 Michael Emanuel35 over 1 year ago

TI__Mastermind 40305 points

Hello,

Can you please confirm the TS voltage at both of these times?

Regards,

Mike Emanuel

0 Keith Haydon over 1 year ago in reply to Michael Emanuel35

Prodigy 130 points

Below are two (2) scope pics showing both NTC Hot & NTC Cold response. CH1 is the Charge_N pin and CH2 is the TS pin

NTC Cold TS pin 1.46 Vdc

NTC Hot TS pin ~ 0 Vdc

0 Michael Emanuel35 over 1 year ago in reply to Keith Haydon

TI__Mastermind 40305 points

Hello,

Can you measure the TS pin with a multimeter? It is possible you are going into Termination and Timer Disable Mode (Section 8.4.6).

Regards,

Mike Emanuel

0 Keith Haydon over 1 year ago

Prodigy 130 points

We will get you the DMM measurement. I don't think we should be going into TTDM as both measurements were taken with the same setup. The only difference was forcing the thermistor hot ( heat gun) and forcing the thermistor cold (freeze spray). The battery was never removed.

0 Michael Emanuel35 over 1 year ago in reply to Keith Haydon

TI__Mastermind 40305 points

Hello,

If the thermistor gets too cold and the voltage on TS rises too high you will go into TTDM.

Regards,

Mike Emanuel

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BQ21040: BQ21040