Simple, Efficient, 1-Cell Li+ Pulse Charger
MAX1879
Functional Diagram
CURRENT-LIMITED
VOLTAGE SOURCE
(800mA)
PFET
REVERSE-CURRENT
PROTECTION DIODE
IN
GATE
MAX1879
PRECHARGE
CURRENT
(8mA)
5mA
CHG
BATT
10kΩ
TSEL
SEE TABLE 2
FOR PULSE-WIDTH
OPTIONS
TIMER
STATE
MACHINE
1.4V
R
ADJ
**
SINGLE
Li+
CELL
1:3
ADJ
2.2µF
1nF
BATT REMOVED
5V
30kHz
OSCILLATOR
HOT
QUAL
TEST
CURRENT
COLD
QUAL
TEST
CURRENT
1.4V
THERM
NTC THERMISTOR
*
*
OPTIONAL—REPLACE WITH 10kΩ RESISITOR IF NOT SENSING TEMPERATURE.
**
R
ADJ
= 410kΩ
±1%
FOR 4.1V CELL; LEAVE OPEN FOR 4.2V CELL.
6
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