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BQ24040: TS pin functionality

Anand M
Prodigy 230 points
Part Number: BQ24040


Hi Team, 

I have a few doubts regarding battery charger IC functionality..

Q1>  We are planned to use BQ24040 Battery charger IC in one of our design. During initial board bring-up, battery charging section will be tested using a normal rechargeable battery (Ex: 18650 without NTC pin).

I have a concern whether the IC still can charge the battery with having TS pin unconnected (left floating).

Q2> What happens if Battery charger IC OUT(output) is bypassed by another supply (say 5V DC) to drive the circuit without connecting a battery & NTC?

  • 0
    TI__Guru* 76736 points

    Hello

    Q1.) -- "I have a concern whether the IC still can charge the battery with having TS pin unconnected (left floating)." -- Bill J -- If the TS pin is floating the unit works similar to a power supply and will charge a battery --- BUT will not terminate and remove power long term this may cause problems for battery.  Check with battery manufacture.  Short term, initial bring-up should be ok.

    Q2.) -- "What happens if Battery charger IC OUT(output) is bypassed by another supply (say 5V DC) to drive the circuit without connecting a battery & NTC?" -- Bill J -- This will not work.  The charger needs to see a voltage in the range of a battery 3V to 4.2V but also needs to deliver current (resistor).

    See Quick Start application note -- SLUA901

  • 0 in reply to Bill Johns
    Prodigy 230 points

    Hi John, Thanks for the Information.

    I am cleared with Q1, where the battery charger goes into TTDM mode if TS pin left open.

    About Q2, I framed it wrongly.

    Actual scenario is : For my BQ battery operated design, I have connected a 10K thermistor to TS pin and connected a two pin battery (without NTC pin) at the OUT. In normal condition (with battery connected at the OUT pin) this works fine as expected. What happens if I just remove the battery connected to OUT pin with retaining 10K thermistor at the TS pin. Whether I will get power at the OUT pin based on the calculated ISet values or NO output??     

  • 0 in reply to Anand M
    TI__Guru* 76736 points

    Hello

    In the configuration with TS 10k separate from battery (OUT).  Remove the battery the and the BQ24040 will go into a battery detect mode.  In this mode current is applied to the OUT for 25mS then for next 25mS device will sink current from OUT.

  • 0 in reply to Bill Johns
    Prodigy 230 points

    Hi Bill Johns, 

    Thanks for the information.