• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 1851 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Single cell Li-ion charger with power path function for GSM based device

Rohan Devardekar
Prodigy 40 points
Other Parts Discussed in Thread: LM22670, BQ24074, BQ24250, BQ24616, BQ24618, BQ24266, BQ24070

Hi,

I am working on project Vehicle tracking system which include main component as GSM module, GPS module and MCU. I have seen some post regarding my requirement but failed to clear my quires. 

I required Single cell Li-ion based battery backup power supply with function of power path management.   

    Requirements for power system:-

Input - Car battery 12Vdc / 24Vdc

output - 3.8Vdc - 4.2Vdc / 2A continues current

Battery used - 3.7V / 1100mAh to 2200mAh Li-ion 

Out of 2A for system most of current required for GSM as 1.5A bust mode while data transmission which will happened after every 10S and in burst mode Current 1.5A required for 577us in 4.615ms For detail i have attached File with this post named as "Burst

Functionality Required:

1) The system should design in the way, it will give 4Vdc when main supply is available and simultaneously charge the battery.

2) When supply cutoff the load aromatically shifted on battery.

3) Two voltage levels required 4V/1.5A for GSM and 3.3V/100mA For GPS and MCU.

4) Charging IC should work Standalone.

Project status:

As mentioned above requirements i have collect data and prepare one logic for this system as 

BQ24074 Liner charger IC followed by Buck of LM22670 and for one LDO TPS79333 

Problem or quries:

1) According to Datasheet BQ24074 will provide current upto 1.5A online supply if the load required more current and the extra current will drawn from battery.

2) The burst mode of GSM will affect the charging topology of battery?

3) Is this system gives proper supply for my device? If not what can i do means like some reservoir CAP at GSM Vcc Pin?  

4) Our should i preferred other component like BQ24250 main reason to avoid this is increase in Pin count and component count required alone with cost also.  

Awaiting for your valuable feedback on this post please give me some solution on this quire. 

    If any other details or any information u want please let me know.

 

Thanks & Regards,

Rohan        

 

  • 0
    TI__Guru*** 144000 points
    The bq24074 maximum operating input voltage is 10.2V so it will not function above that voltage. Even it would function, the power dissipation of a linear charger from a 12V input supply down to 4.2V at 1.5A would be so high that the charger would likely run in thermal limit, thereby reducing the allowed current flow. I suggest a switching charger. The bq24266 with up to 13.5V operating input voltage might be a good option. If you need up to 24V input, then I suggest you look at bq24616 or bq24618.
  • 0 in reply to Jeff F
    Prodigy 40 points

    Its not the issue of of input voltage because i m using Buck regulator before bq24074 to convert 12Vdc / 24Vdc to 5Vdc which is input for bq24074.

    The main problem is the online current limit of bq24074 is 1.5A but in my system GSM module alone req 1.5A burst current but its not continuous as i mentioned in my quires.

    So is it possible to use bq24074 for this application which has max current of 1.6A?  

  • 0 in reply to Rohan Devardekar
    TI__Guru*** 144000 points
    We cannot warranty the operation above the 1.5A rating per the datasheet. I suggest oversizing the capacitance on the OUT pin to help supply the additional current when a battery is not present and the IC cannot enter supplement mode.
  • 0 in reply to Jeff F
    Prodigy 40 points

    Thank you Jeff for your valuable reply,

    but still i am Confused to use BQ24074 for my application. can you please insure about its working with GSM module which is pick of 1.5A some times and some extra current of less than 100mA for Other components    

    The GSM module will take these current burst while start-up and data send / receive which event going to happen after every 10 Seconds say for 3 to 4 sec.

    For these 3 to 4 sec also it is not continuous 1.5A  but in terms of pick pulses for 577us after every 4.615ms as i mentioned earlier. Please suggest me some rigid solution.

     

  • 0 in reply to Jeff F
    Prodigy 40 points

    Thank you Jeff for your valuable reply,

    but still i am Confused to use BQ24074 for my application. can you please insure about its working with GSM module which is pick of 1.5A some times and some extra current of less than 100mA for Other components    

    The GSM module will take these current burst while start-up and data send / receive which event going to happen after every 10 Seconds say for 3 to 4 sec.

    For these 3 to 4 sec also it is not continuous 1.5A  but in terms of pick pulses for 577us after every 4.615ms as i mentioned earlier. Please suggest me some rigid solution.

     

  • 0 in reply to Rohan Devardekar
    TI__Guru*** 144000 points
    If a battery is present, then the IC will go into supplement mode and provide the additional current from the battery. If a battery is present, then the IC will enter current limit during the 3 to 4 sec pulse. You could need a capcaitor sized as C = (Ipulsepeak - 1.5A)*dv/4 sec where dv is the voltage droop you are willing to accept. You might consider moving to the bq24070 IC, which allows for up to 2-A input current limit.