Rainbow Electronics MAX8903A - Manual (Page 13)

MAX8903A
2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power
______________________________________________________________________________________ 13
The IC includes a full-featured charger with thermistor
monitor, fault timer, charger status, and fault outputs.
Also included are power-OK signals for both USB and
DC. Flexibility is maintained with adjustable charge
current, input current limit, and a minimum system volt-
age (when charging is scaled back to hold the system
voltage up).
The MAX8903A prevents overheating during high ambi-
ent temperatures by limiting charging current when the
die temperature exceeds +100°C.
DC Input—Fast Hysteretic
Step-Down Regulator
If a valid DC input is present, the USB power path is
turned off and power for SYS and battery charging is
supplied by the high-frequency step-down regulator
from DC. If the battery voltage is above the minimum
system voltage (V
SYSMIN , Figure 4), the battery charger
connects the system voltage to the battery for lowest
power dissipation. The step-down regulation point is
then controlled by three feedback signals: maximum
PG
PG
DC
DC
BST
LX
LX
CS
CS SYS
SYS
BAT
BAT
FLT
UOK
DOK
FAULT
OUTPUT
USB PWR OK
DC PWR OK
TO VL
R PU
4 x 100k Ω
18
19
8
24
23
21
20
1
2
3
4
6
27
28
25
26
17 USB
ISET
IDC
R ISET
R
IDC
DCM
THM
CEN
IUSB
GND
NTC
10k
Ω
USUS
5
9
16
12
CHARGE ON
OFF
100mA
500mA
USB SUSPEND
14
7
15
TO SYSTEM
LOAD
CHG
22 CHARGE
INDICATOR
C DC
4.7 μF
CT
C CT
0.15 μF
L1
1 μH
C BST
0.1 μF
13
11
10
RT
10k
Ω
TO SYSTEM LOGIC
1-CELL
LI+
C BAT
10 μF
C SYS
10 μF
VL
MAX8903A
VBUS
D-
D+
ID
GND
SERIES
MINI-B
C VL
1 μF
Figure 3. Typical Application Circuit Using a Mini 5 Style Connector or Other DC/USB Common Connector