We have a design using the LTC4065L with an 820-Ohm PROG resistor. According to the datasheet for the LTC4065L this should provide about 250mA of charge current when the LTC is in constant current mode. There is a circuit drawing about 2mA of power with the battery while the battery is charging from a 5V dc source. We have a current meter in series with the battery to measure charge current.
I'm having trouble understanding what I'm seeing when we enable charging. First, the maximum charge current on a deeply discharged (3V) single Lipo battery is only 177mA as measured by the current meter. Second, the LTC4065L always seems to be in constant voltage mode. I never see a constant charge current into the battery. The measured current starts at 177mA and slowly decreases as the battery charges. I expected to see a constant charge current into the battery until the battery approached about 4.1V and then see the current start to drop.
I know I must be missing something important or I'm misunderstanding my measurement setup. Might someone there have some idea what I'm missing?
Thank you.