Electronics > Beginners
LiPo charger MCP73831 indication LED
khiworld:
Hi.
I am using the MCP73831 Battery charger for my design. I decided to add 2.7k ohm resistor at the PROG pin. So, Ireg is set to 370mA.
LTST-C195KG, dual color chip led is connnected between the VDD and STAT pins for status indicator.
Pin2 and 4 - RED
Pin1 and 3 - Green
When testing the circuit, I got three different cases..
1. The red LED lights when charging and green when finished.
2. The red LED is on when charging and the red light wont turn green.
3. Red while charging, both Red and green when charged.
Any thoughts?
Peabody:
What is the function of the resistor labeled "21" which appears to be a load resistor? You've used the MCP73831, which has no load sharing circuitry. So you can't have any load current while the battery is charging - it can confuse the charger if the load current is more than the cutoff current to terminate charging, so it would never stop charging. That could be case #2. I don't know what #3 is all about.
The MCP73871 has load sharing, which permits running the device while charging the battery. It might be a better choice.
You can't have the charger not terminate charging. That's a safety issue because it can lead to explosions.
khiworld:
Hey Peabody,
Thanks for the reply. The labeled "21" is not a load resistor. It is the symbol for the Li-ion battery. I am sorry to confuse you.
Peabody:
Sorry I was confused.
According to the datasheet, scenario #1 is the normal result when charging is successful. Scenario #2 would indicate that charging has not completed. Scenario #3 occurs in shutdown mode, which is when the supply voltage is too low. See Section 4.
khiworld:
Yes, I agree with you opinion. but, I would like to figure out what causes case #2.
While charging, LDO(MIC5504) is working..It means that the current is drained from LDO so the charge never ends.. As you can see the attached file, the input current of LDO is sum of I_load and I_GND.
The amount of current drained from LDO cannot be ignored....this is what I am guessing..
If I am right, the solution would be adding pmos between J2 and C3.
Please correct me.
Navigation
[0] Message Index
[#] Next page
Go to full version