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bq24070 and dynamic load switching

chaitanyab
Intellectual 620 points
Other Parts Discussed in Thread: BQ24070

Hi,

 

I am designing for a GSM/GPRS application.Here the Digital load(uC and Modem etc) can take upto 4.0 Volts(absolute Max) and 3.3V recommended.

I am planning to use bq24070 as a charger and give its Vout to my  digital load.

I am planning for Li-ion Single cell 3.6V ,950 mAH Battery.

The Adapter gives 5.0 V DC.

In Case of Adapter Present, can the bq24070 regulate the DC to 3.3 Vout?

When the charger will cutoff the battery ?2.65V?Will it try to boost this voltage on Vout?

Do you recommend any Buck-boost after the Charger my load current and voltage requirement is 3.3V ,2.2A?

 

  • 0
    TI__Mastermind 32400 points

    Hi Chaitanyab,  

    I am planning for Li-ion Single cell 3.6V ,950 mAH Battery.>> This charger should handle this battery.

    The 5V input voltage to the charger is good.

     

    The system load is powered directly from the AC adapter through the internal transistor Q1. The output is regulated at 4.4 V (bq24070). You need to step it down to 3.3V for your digital load.

     

    During a charge cycle, if the battery voltage is below the V(LOWV) (3V) threshold, the bq24070/1 applies a pre-charge current, IO(PRECHG), to the battery. This feature revives deeply discharged cells. The RSET resistor, connected between the ISET1 and VSS pins, determines the pre-charge rate.

     

     

    Thanks!

    Tahar

  • 0 in reply to Tahar Allag
    Intellectual 620 points

    Hi Tahar,

     

    Thanks for a such a quick reply !

    I have further few questions:

    1.The Voltage Regulation for the system power supply on the Vout Pin,Will this be functional when the battery is Switched ON(No adapter input)?How it will regulate or step up if the battery voltage, say 3.2V battery to 4.4V?I don't see any inductor around !I think I will need a buck boost to regulate the voltage to 3.3V. Pls comment !!

    2.The NTC thermistor mentioned,is it has to be the integral part of the battery?Can I mount the NTC externally on the Battery and sense the temperature?Basically why do you require NTC for Charger?

    3.What is the maximum capacity of the battery that can be charged by this charger?

    4.How to determine the charging current?I need to calculate a gross estimation to determine the time required to charge the battery

    5..Do you recommend any Battery manufacturer?Any external battery that is tested with this charger?

    6.It is written that the charger IC will be functional upto 18V VIN, How much is the  Vout  and Iout is supported by the requlator,say if I use 12V Vehicle Battery as a Adapter input?It looks like it is a linear regulator,I have 2.5A load for 4.4 V will this work for 12V VIN? I am trying to save on 1 Buck converter from 12V to 5V as a Adapter in?

    7.Do you recommend any Battery Fuel Gauge?I have a 3.6Li-ion single cell battery 950 -300 AH

    8.Can I use a Power Supply Monito IC Like TPS3808G33 to monitor the Battery voltage,I mean can I keep it connected to  the  Battery and while it is charging in different phases?

  • 0 in reply to chaitanyab
    TI__Mastermind 32400 points

    Hi chaitanyab,

     

    Answers for your questions are included in the attachment.  

     

    Thanks!

    Tahar

    Answers.doc