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TLV3401: Low battery cutoff for discharge management

Ibrahim Qasim
Intellectual 680 points
Part Number: TLV3401
Other Parts Discussed in Thread: TPS61030, BQ24650, , TLV3012, TPS3700EVM-114

Hello,

I have recently purchased the TLV 3401 to ensure my 3.7 V 6000mah battery does not overdischarge by adding a low battery cutoff and release at 3.2 V and 3.3 V respectively to disable my loads.

Here is the schematic of my entire design:

Schematic_Final base model_2020-10-28_12-38-22.pdf

My solution looks at disabling voltage coming into pin 8 of the TPS61030 converters (U4 and U8) by attaching a comparator at the VBat output of my BQ24650 charger. How would I implement a noninverting comparator with hysteresis with the use of the TLV3401 for my battery??

I have attached a simpler diagram of my configuration: ( Please disregard the 3V trinket. The MCU being used will be an arduino nano powered by one of my TPS61030 boost converters)

LTC config (3).pdf

  • 0
    TI__Genius 10455 points

    Hi, 

    This cookbook will help you implement external hysteresis with the TLV3401. Please reply with any additional questions you have.sboa313a.pdf

    Thanks,

    Joe

  • 0 in reply to Joe Vanacore
    Intellectual 680 points

    Hello Joe,

    I have seen this cookbook before, I just was not sure how to implement it... I did however refer to the schematic and section 9.2:  

    I am aware that the TLV 3401 does not have a built in internal reference so I simulated it with a 5 V source and a resistor divider of R1 = 220k and R2 = 470k. I also powered the comparator directly from the battery and connected it to my pullup resistor connected at Vout. How would I add hysteresis to this and is a regulator/internal reference necessary for my application?? My voltage source alters between 2.4V to 4.2V and I have an overvoltage protection from the BQ24650. The TLV3401 was purchased as a means of testing out a simple prototype to interface with my design and see if this fixes my low battery cutoff issue. Should I scrap using this comparator for a different one such as the TLV 4021R1??

    Note: I do not have a stable voltage source in my project, my solar panel and battery voltage vary all the time. For the output of my battery I require currents of up to 3 A with minimal losses

  • 0 in reply to Ibrahim Qasim
    TI__Genius 10455 points

    Hi,

    To implement external hysteresis, you do not need a built-in internal reference. I will attach an excel tool to help you calculate the resistor values that you need for external hysteresis in your design. From what I can tell the 5V source will be your reference voltage?

    If the supply voltage for the device is below the recommended operating voltage then the operation of the TLV3401 is not warrantied. If the voltage goes below 2.5V or 2.7V, depending on the version of the part, it is outside of the recommended range.

    If you need a comparator with a wider supply range and an internal reference, then you could use the TLV4041R1.

    4532.comparator_hyst_tool.xlsx

    Regards,

    Joe

  • 0 in reply to Joe Vanacore
    Intellectual 680 points

    Good morning,

    Thanks for the excel tool, it helped immensely in the design process. I do however have some questions regarding the input voltages of the comparator.

    I have a 3.7V 6000 mah battery and I am using the comparator as an undervoltage detector. With a VL output cutoff, I presume I am looking for a noninverting topology. In this case, am I looking at connecting my battery inputs to Vdiv Vcc and Vpu?? Also, if those are the inputs to which my battery is connected, what is the Vin at the non inverting input for?? 

    Thanks,

    Abe

  • 0 in reply to Ibrahim Qasim
    TI__Genius 10455 points

    Hi Abe,

    I am glad that the excel tool helped.

    In regards to your question, it sounds like you don't intend on using an external reference. Thus, I recommend using the TLV3012 with a 1.242V internal reference. It is a push-pull device as well so there is no need for a pull-up resistor.

    This would allow you to supply the comparator with the battery and use it as an input to the device.

    On page 8 of the TLV3012 datasheet, there is an example "Battery Level Detect Circuit".

    Regards,

    Joe

  • 0 in reply to Joe Vanacore
    Intellectual 680 points

    Joe,

    Thank you very much for your help! I have ordered the TPS3700EVM-114 for testing purposes with my system to see how the discharge and charging with my battery charger would take place. I will go ahead and swap out R1 in that system with a 604kOhm resistor to better match my required threshold. I shall take the TLV3012 into consideration for the final model. 

    Thanks again!

    Abe