Data Sheet

FB
CN3083
BAT
4.7uF
8
5
Rx
Vbat
4.7uF
GND
VIN
3
4
Input Voltage
Figure 5 Adjusting Regulation Voltage in Constant Voltage Mode
In Figure 5, the regulation voltage in constant voltage mode will be given by the following equation:
Vbat ＝ 4.2＋3.04×10
-6
×Rx
Where,
Vbat is in volt
Rx is in ohm
Programming Charge Current
The formula for the battery charge current in constant current mode is:
I
CH
= 1800V / R
ISET
Where:
I
CH
is the charge current in ampere
R
ISET
is the total resistance from the ISET pin to ground in ohm
For example, if 500mA charge current is required, calculate:
R
ISET
= 1800V/0.5A = 3.6kΩ
For best stability over temperature and time, 1% metal film resistors are recommended. If the charger is in
constant-temperature or constant voltage mode, the charge current can be monitored by measuring the ISET pin
voltage, and the charge current is calculated as the following equation:
I
CH
= (V
ISET
/ R
ISET
) × 900
Combine Two Power Inputs
Although the CN3083 allows charging from a solar power supply, a wall adapter or a USB port can also be used
to charge Li-Ion/Li-polymer batteries. Figure 6 shows an example of how to combine 2 power inputs. A
P-channel MOSFET, M1, is used to prevent back conducting into the 2
nd
power supply when the 1
st
power
supply is present and Schottky diode, D1, is used to prevent 2
nd
power supply loss through the 1kΩ pull-down
resistor.
REV 1.1 8