I'm trying to create a stand alone battery charger for a single 18650 battery.
For this I created the Schematics and PCB found here.
But during the charging only charges with <1A (differential measured over the sense resistor <20mV/20mohm) instead of the calculated 1.6A in constant current mode with an average voltage of 3.90V.
Is there anything I missed while designing the schematic? Because I supply it currently with a lab power supply of 5V and 5A.
I think the schematic looks good. You should make sure that you have some headroom between your input voltage and your battery. For example, be sure that your voltage is not drooping due to resistive losses by the point that it connects to the board.
If you can read registers from the chip, that may help to determine what is going on.
I do see some problems with the layout. For one thing, the thermal relief is not recommended as part of the switcher circuit, or for passing power. I recommend that you remove it from all components that will pass power and caps associated with that path.
There is a recommended layout for this part which is on page 35 of the datasheet.
This looks like a 2-layer board, correct? For this current level, that should be ok, but it looks like your IC's GND paddle does not have vias connecting it to a GND plane.
I'm going to send you design files (privately) for our demo board which is releasing soon. You can use this as a reference.
Thank you for your response,this is indeed a 2 layer board. I used the thermal relief to make it easier to solder by hand.
There is a big hole in the middle of the thermal pad that is connected to the ground plane on the bottom side.
I did some measurements and it seems I need a minimum of 5.4V on my power supply to activate the charging. As soon as I lower it to 5.3V this stops the charging when I measure this voltage with my scope it is on the LTC4162-L 4.92V and with a input of 5.4V it is 5.00V. This is strange because the datasheet states that a minimum of 4.5V is needed.
Sounds like you have some voltage drop on the way to the circuit. Keep an eye out for this in the circuit as well. You may want to look the VIN / VOUT voltages with a scope and trigger on a low voltage to see if there is additional drop when it tries to start charging - that could instantaneously drop below the 4.5V UVLO.
I am devemin from Japan.
I try to make 18650-charger too.
I asked local agency to get demo's design & PCB sample layout files in Japan, but they said that DC2038 is until not release, so I can't get these files.
Can you send me design & sample layout files (privately) ?