MAX1552 Datasheet, PDF (8/12 Pages) Maxim Integrated Products – Complete Power IC for Low-Cost PDAs

Complete Power IC for
Low-Cost PDAs
AC ADAPTER INPUT
3.5V TO 7V
DC
1µF
USB INPUT
3.5V TO 6.0V
USB
1µF
MAX1551
BATT
POK LOW WHEN ^PG
EITHER USB OR DC
IS ABOVE UV AND
ABOVE BATT
GND
BATTERY
CHARGER
V_IN
C1
1µF
TO MAIN
POWER
PRESENT
(EITHER DC
OR USB)
SDIG
ON
OFF
COR2
ON
OFF
LCD
ON
OFF
IN
MAIN
SWIN
SDIG
MAX1552
C8 ^REF
0.1µF
COR1
ENSD
COR2
ENC2
SW
ENLCD
MAIN
LX
R3
R4
1MΩ
1MΩ
LFB
RESET OUT
RS
LOW BATT OUT
LBO
GND
3.3V, 300mA
C3
4.7µF
3.3V, 200mA
C5
4.7µF
1.5V, 200mA
C4
4.7µF
1.8V, 20mA
C6
1µF
L1
10µH
D1
C7
30pF
C9
4.7µF
LCD 20V, 1mA
R1
1.5MΩ
C2
1µF
R2
100kΩ
CONNECTION FOR
PWM-CONTROLLED
LCD BIAS
R_W
R_D
V_WOUT
C10
Figure 1. Typical Operating Circuit with Charger and External PWM LCD Control
Voltage Monitors (LBO)—System Sleep
The MAX1552 monitors the battery voltage at IN. When
V_IN falls below 3.6V, LBO goes low, typically putting the
system (µP) into a sleep state. The MAX1552 remains
fully functional in this state and all outputs maintain nor-
mal operation. However, when in sleep mode, the sys-
tem (µP) typically drives ENSD, ENC2, and ENLCD low,
turning off COR2, SDIG, and the LCD boost output.
Sleep can be set by the system (µP) even without a low
battery event. The MAX1552 consumes 50µA when the
system is in sleep mode. The LBO output is deasserted
when the battery voltage rises above 3.8V
All regulated outputs turn off when V_IN falls below 3V.
The MAX1552 resumes normal operation when V_IN
rises above 3.4V.
Reset Output (RS)
Reset (RS) asserts when V_IN goes below 3V. The reset
output remains asserted until V_IN rises above 3.4V. RS
is an open-drain, active-low output. Connect a 1MΩ
resistor from RS to MAIN.
Applications Information
LDO Output Capacitors (MAIN, SDIG,
COR1, and COR2)
Capacitors are required at each output of the MAX1552
for stable operation over the full load and temperature
range. See Figure 1 for recommended capacitor values
for each output. To reduce noise and improve load
transients, use large output capacitors, up to 10µF.
Surface-mount ceramic capacitors have very low ESR
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