USB-Powered Li+ Charger
Use a larger input bypass capacitor for high input volt-
ages or high charging current to reduce supply noise.
Charging from AC Adapters
The MAX1811 also operates from sources other than
USB ports. The full charging input voltage range is
4.35V to 6.5V. When charging in the 500mA mode with
an AC adapter, rely on the thermal loop to limit the
power dissipation by limiting the charge current at
higher input voltages if limited PC board area is avail-
able to dissipate heat.
Chip Information
TRANSISTOR COUNT: 1907
PROCESS: BiCMOS
Capacitor Selection
Use a minimum of 2.2µF placed close to BATT for prop-
er stability. Bypass IN to GND with a 4.7µF capacitor.
HOST OR
POWERED HUB
LOW-POWER
FUNCTION
BUS-POWERED
HUB
4.375V
4.625V
*4.400V
4.640V
0.110V
4.750V
4.397V
0.003V
4.378V
0.002V
4.735V
0.015V
4.500V
4.350V
0.000V
0.000V
0.125V
0.025V
REFERENCED REFERENCED
TO SOURCE TO HUB
*UNDER TRANSIENT CONDITIONS, SUPPLY AT HUB CAN DROP FROM 4.00V TO 4.070V.
Figure 3. USB Voltage Specification
TO LOAD
BATT
SINGLE
Li+
CELL
IN
4.35V TO 6.5V
4.2V
SELV
4.1V
TO IN
ON
MAX1811
LED
EN
OFF
CHG
GND
GND
500mA
CHG
LOGIC OUT
SELI
100mA
10k
Figure 4. Charging from a USB Port
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
