Rainbow Electronics MAX8922L - Manual (Page 11)

USB Charge
The universal serial bus (USB) provides a high-speed
serial communications port as well as power for the
remote device. The MAX8922L can be configured to
charge a single Li+ battery at the highest current possi-
ble from the host port. Figure 5 shows the MAX8922L as
a USB battery charger. The microprocessor enumerates
the host to determine its current capability. The system
can program the charge current to 90mA, I
SETI
, or
400mA by EN/SET pulses if the host port is capable. The
MAX8922L also provides an overvoltage-protected 4.94V
LDO output to a low-voltage-rated USB system input.
GSM Test Mode
Figure 6 shows the MAX8922L in a GSM test mode. By
sending three pulses to EN/SET, the MAX8922L goes
into GSM test mode. GSM PA can pull up to 2.3A for
576µs once every 217Hz from the MAX8922L’s output.
The configuration in Figure 6 is used for system devel-
opment, testing, and calibrations in the production or
design stage.
MAX8922L
30V Li+ Linear Battery Charger
with GSM Test Mode in 3mm x 2mm TDFN
______________________________________________________________________________________ 11
USB
CABLE
IN BAT
EN/SET
GND
LDO
EP
POK
CHG
SYSTEM
VBUS
GPIO
GPIO
GPIO
R1
1.87k Ω
C1
1 µF
C2
2.2
µF
C3
1
µF
VI/O
4.2V
Li+
R2
3k Ω
TEST
MAX8922L
MIN
SETI
Figure 5. USB-Powered Li+ Battery-Charger Application