resistor selection for TPS3700DDCR undervoltage circuit

by Aubrey Champagne   Last Updated June 30, 2020 04:25 AM

I am designing an undervoltage circuit for a lipo battery project. I found this tutorial here which lead me to the TPS3700. I am wanting the undervoltage condition to be 3 volts. The part that I am hung up on is choosing the right resistors for the under and over voltage conditions. At the bottom of page 16 of the datasheet, it says Rt=R1+R2+R3 and Select a value for RT such that the current through the divider is approximately 100 times higher than the input current at the INA+ and INB– terminals. I'm having trouble figuring out this value. The max current that would be going through the power rail is 650 milliAmps. Also the equations for R3 and R2 have a term Vit+ which is defined as Positive-going input threshold voltage. Texas Instruments also says it's The input threshold voltage when the input voltage is rising., but this doesn't really give me much detail on how to calculate it. I calculated Vit+ from the tutorial and found this value to be around .4001 I used this value along with their Rt for my resistors and assembled the circuit below: enter image description here

boost gate just leads to a mosfet that controls a 3.7 to 5V boost circuit. Will these resistors cause the undervoltage condition to be 3V? The specific values for the battery I am using is 3.7V 800mAh.



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