I completed my circuit design with the help of the schematic found on the datasheet of the MP2639B and the datasheet of the EV2639B-R-00A Evaluation Kit. The following are my design schematic:
The three batteries are connected parallel to each other, so they act as single cells. The CHGOK led is blinking on the circuit right now.
I don’t know what I should do. If you can help I’d appreciate it. I also have a few more questions.
First, it seems that the MP2639B’s datasheet has a connection to the NTC pin by the GND of the battery. But the EV2639B-R-00A schematic does not have this connection. Should I connect the battery’s GND to the NTC pin? I made this connection with an external cable, but still the CHGOK led continued to blink.I marked the ties I mentioned in red.
Another question is that the EV2639B-R-00A schematic used normal resistor in RNTC1 and RNTC2. So, based on this, I used a normal resistor. I don’t understand if I need to use my ntc resistor here or a normal resistor.
Thanks in advance for your help.
The evaluation board essentially disables the NTC function by dividing the reference voltage to a midpoint that keeps the NTC fault from tripping. It won’t matter where the ground is for the NTC reisistor if you do that. The actual function will have the NTC resistor placed at next to a battery cell to monitor the temperature at that point. For your test purposes leaving the fixed resistors in place with the board ground is OK. Use a DVM and measure the voltage at the NTC pin to make sure its in the correct range. With the CHGOK light blinking and NTC voltage OK, that means the charging time has expired, so check that the TMR capacitor is connected and value is correct, and that the battery hasn’t been charging longer than the timer set time.