Microchip Technology MCP73871DM-VPCC Manual Do Utilizador

DS51812B-page 12

© 2009 Microchip Technology Inc.

The MCP73871 Demo Board with Voltage Proportional Current Control is fully 
assembled and tested for charging a single-cell Li-Ion or Li-Polymer battery with or 
without system load.

2.3.1.1

POWERING THE MCP73871 DEMO BOARD WITH VOLTAGE 
PROPORTIONAL CURRENT CONTROL

1. Connect the positive battery terminal to V

BAT

+ (TP4) and negative battery 

terminal to GND (TP1 or TP5).

2. Connect the 5V – 6V DC power supply Negative Terminal to GND (TP1 or TP5).
3. Connect the 5V – 6V DC power supply Positive Terminal to V

DD

 (TP2).

4. Connect positive of load to OUT (TP3) on the board and negative of load to GND 

(TP1 or TP5). The system load can be a power resistor or E-Load.

5. The maximum current that system load requires should not violate the 

specification of Li-Ion battery manufacturer (typical at 1C or less) or 1A for safety 
and performance concerns.

6. You should initiate the battery charging cycle when turning CE switch of S1 OFF. 

Turning the CE switch ON disables the Li-Ion battery charger function.

7. The S1 switch #1 in OFF position (SEL - “AC-DC”) allows maximum input current 

of 1.8A to support both system load and Li-Ion battery charger at 1000 mA fast 
charge current rate.

8. The S1 switch #1 in ON position (SEL - “USB”) limits the input current to meet 

USB specifications.

9. If switch SEL is in ON position (PROG2), the user has two options for switch #2:

- OFF - limits the total input current to 500 mA
- ON - for maximum input current at 100 mA.

10. If DC power is removed, the load should be supported by the Li-Ion battery.

The resistors that connected at R

PROG1

 and R

PROG3

 pins select the maximum charge 

current in constant current mode from ac-dc adapter and termination current, 
respectively. The relationship between fast charge current and value of R

PROG1

 

resistor is illustrated in Figure 2-1. The correspondence of R

PROG1

 on MCP73871 

Demo Board with Voltage Proportional Current Control is R

1

. The default value is 1 kΩ, 

which sets the maximum charge current at 1A.
For R

PROG3

, the correspondent resistor is R

2

. A 10 kΩ resistor sets the charge 

termination current at 100 mA and a 100 kΩ value results a 10 mA termination point. 
Read carefully the additional information on the schematic in A.2 “Board – Sche-
matic”. The boards comes with R

2

 =10 kΩ.

Note 1: For setup/configuration follow the information in Table 2-2.

2: Fast Charge Current and Termination Current can be easily programmed 

with various resistors based on Figure 2-1.

3: The Li-Ion battery pack can be replaced with test circuit or electronic load 

that can sink current with DC power supply. Refer to Figure 2-2

for 

details.