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bq27510 without external thermistor... and other basics

Jakub Pilat
Prodigy 20 points
Other Parts Discussed in Thread: BQ27510, BQ27510-G2

Hi

It is my first post here, and i have few pretty basic questions. I am working on project that is going to use bq27510 as fuel gauge. Datasheet gives quite solid info about this IC but it does not clearly explain the configuration without external thermistor (useing internal one instead). I know how to reconfigure it to use internal temperature measurment, but what am i supposed to do with remaining TS pin. I guess that i can leave it unconnected,  not sure though. Additionally in recommended design the BI/TOUT pin is pulled up through 1.8M resistor to 2.5V Vcc, and through battery pack thermistor to GND (cell connection pulls BI/TOUT low = battery connected). Because my battery  won't have built in thermistor, can I just connect BI/TOUT pin to battery GND (in my opinion it will work the same as with thermistor)?

Ps. Beacause it is a single device project, i am not going to buy EV2300 just to calibrate one bq27510 with bqeasy soft, so could anybody approximately describe its accuracy without additional calibration? Is it possible not to do it?

Anyway, thanks in advance for any answear.

Kuba

  • 0
    TI__Expert 4050 points

    Kuba,

     

    The TS connection not only for temperature measurement but also serve as part of the BI detection through the thermistor network. Since you are using int temp sensor, I would connect a 10k from TS to ground. If your battery will never be removed, i.e, you don't need a battery insertion (BI) detection then just connect 18k from TOUT to TS. 

    The calibration is required as it will affect the gauging accuracy.

     

    Thanks

    Ming

  • 0 in reply to Ming Yu
    Prodigy 20 points

    Hello again

    I have returned to my project after a short break:), and i am still willing to use bq27510, but have a new question. Is it possible to power the  IC  (the REGIN pin) from different source than battery? The bat pin obviously will be connected to battery (if inserted), but i want to connect the REGIN input to some other power supply, not necessary equal to battery voltage but within recommended 2.7V-5.5V. Got to design it like that, otherwise after battery removal, the IC will be powered down and I won't be able to use  BI/TOUT pin for battery removal detection (BI/TOUT=high), when there is no battery...

    Thanks for any reply

     

    Kuba

  • 0 in reply to Jakub Pilat
    TI__Expert 4050 points

    yes, you can use other voltage source than battery. The gauge will be powered up even if battery is removed. BI/TOUT is still working even with battery connected to REGIN because that is part of the gauge power up initialization process.

  • 0 in reply to Ming Yu
    Prodigy 10 points

    Hey,

    I'm trying to use the bq27510-g2  in my product and we built our first boards.  

    I hooked the battery termisor to the charger, and planned on using the internal temp sensor.  But I didn't know TS was part of battery detection with BITOUT.   I have BITOUT connected, to a resistor network that looks like a termistor is present, but I left TS floating.    The problem is we aren't seeing any updates, it just shows 0V, 293K, no goot OCV reading, basically nothing.    Is the TS floating causing this?  Is there any workaround is firmware?

     

    Thanks,