MAX8814 MAXIM [Maxim Integrated Products], MAX8814 Datasheet - Page 9

• Manufacturer Part Number: MAX8814
• Description: 28V Linear Li+ Battery Charger with Smart Autoboot Assistant
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 4. USB Battery Charger
Figure 3 shows the MAX8814 as a microprocessor-
cooperated Li+ battery charger. The MAX8814 begins
charging the battery when EN is low. The microproces-
sor can drive EN high to disable the charger. The
MAX8814 generates a POK signal to indicate the pres-
ence of an input supply. By monitoring V
tem can measure the charging current and decide
when to terminate the charge.
The universal serial bus (USB) provides a high-speed
serial communication port as well as power for the
remote device. The MAX8814 can be configured to
charge a battery at the highest current possible from
the host port. Figure 4 shows the MAX8814 as a USB
battery charger. To make the circuit compatible with
either 100mA or 500mA USB ports, the circuit initializes
at 100mA charging current. The microprocessor then
enumerates the host to determine its current capability.
If the host port is capable, the charging current is
increased to 425mA to avoid exceeding the 500mA
USB specification.
USB PORT
Microprocessor-Interfaced Charger
_______________________________________________________________________________________
GND
VBUS
USB-Powered Li-Ion Charger
28V Linear Li+ Battery Charger with
Application Circuits
1μF
C1
ISET
IN
ABI
ABO
GND
, the sys-
EP
Smart Autoboot Assistant
MAX8814
Place the input and output capacitors as close as pos-
sible to the IC. Provide a large copper ground plane to
allow the exposed paddle to sink heat away from the
IC. Connect the battery to BATT as close as possible to
the IC 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
MAX8814 Evaluation Kit to speed designs.
PROCESS: BiCMOS
ISET
R2
15.8kΩ
BATT
POK
EN
N
R5
4.99kΩ
10kΩ
C3
2.2μF
R4
V
I/O
R3
1MΩ
+
Li+
C4
0.1μF
Layout and Bypassing
Chip Information
ON
GPIO
GPIO
ADC
GPIO
SUPPLY
SYSTEM
POWER
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