BQ2004: C°/min value of Delta T/ Delta t termination condition

Hi Kevin,

   BQ2004 samples the voltage at the TS pin (which corresponds to temperature increase) every 34s and compares it to two samples before (1 minute). For nimh, as the cell is overcharged temperature will start to increase, which is why this is a valid termination scheme. This depends on the battery and charge current, as battery will heat up quite quickly depending on how much current you are charging with. You can control the voltage at TS as the thermistor is essentially just a resistor in parallel with the bottom resistor of the voltage divider. As the temperature increases, the resistance of the thermistor will change, which will change the voltage on TS and this is the 16mV/min change that BQ2004 is monitoring for termination of fast charge.

  Essentially for the rate of 0.6C/min you want to observe the resistance change from your thermistor datasheet that occurs between 0.6C and equate it to the TS voltage changing by 16mV so that you can size your top and bottom resistors of your voltage divider accordingly.