Datasheet

MAX8808X/MAX8808Y/MAX8808Z
USB-Powered Li+ Charger
The universal serial bus (USB) provides a high-speed
serial communication port as well as power for the
remote device. The MAX8808X/MAX8808Y/MAX8808Z
can be configured to charge a battery at the highest
current possible from the host port. Figure 5 shows the
MAX8808X as a USB battery charger. To make the cir-
cuit compatible with either 100mA or 500mA USB ports,
the circuit initializes at 100mA charging current. The µP
then enumerates the host to determine its current capa-
bility. If the host port is capable, the charging current is
increased to 425mA to avoid exceeding the 500mA
USB specification.
Layout and Bypassing
Place the input capacitor as close to the device as pos-
sible. Provide a large copper ground plane to allow the
exposed paddle to sink heat away from the device.
Connect the battery to BATT as close to the device as
possible to provide accurate battery voltage sensing.
Make all high-current traces short and wide to minimize
voltage drops. A sample layout is available in the
MAX8808 evaluation kit to speed designs.
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
10 ______________________________________________________________________________________
MAX8808XETA
INVBUS
GND
4.2V
Li+
C2
1µF
C1
1µF
USB PORT
ISET
EN
CHG
SYSTEM
VL
BATT
R2
13kΩ
R4
100kΩ
GND
C3
0.47µF
N
V
I/O
V
I/O
ACOK
R3
100kΩ
R1
4kΩ
HIGH: 425mA, LOW: 100mA
D+
D-
Figure 5. USB Battery Charger