LTC4124 EVB Charging Problem (DC2770A-B KIT)

I have purchased and tested an EVM board (DC2770A-B Kit) for LTC4124 100 mA, but the charging current is only 30 to 40 mA.
If you have released the assessment board, you may have previously charged to 100 mA.

Question 1) The configuration of the assessment that the charging current of the assessment board is 100 mA and the results of the test that confirmed that 100 mA is being charged

Question 2) The evaluation board for 50 mA charging is charged using the full bridge method using SW2. The evaluation board for 100 mA is charged using the Half Bridge method instead of SW2.
I'd like to know why I made a 100 mA evaluation board using the above method.

Test Condition : DC2770A-B KIT + BAT(470mA, 4.2V) 

  • 0
    •  Analog Employees 
    on Nov 25, 2019 4:12 PM

    Hi Mike,

    Could you check the BAT pin voltage on your LTC4124 board when you see 30 to 40mA of charge current? The impedance of the cable you used to connect the battery may cause the BAT pin to be close to 4.2V when charging. According to the charging profile of LTC4124, this could cause the LTC4124 to reduce the charging current. 

    Answers to question 1) I'm not quite sure what your question is. In the lab I do see 100mA for the 100mA board.

    Answers to question 2) You are right that the 50mA uses the full-bridge of LTC4125 while the 100mA version uses only the half-bridge of the LTC4125. That is becauce the 100mA uses optimum power search method of the LTC4125, and it requires a finer step voltage size for LTC4125 to make it work better. Please also check our technical article below for a more detailed explanation. 

    https://www.analog.com/en/technical-articles/complete-efficient-100-ma-wireless-charging-solution-with-optimum-power-transfer-and-safety-features.html

    Thanks,

    Wenwei.