MAX1559 Datasheet, PDF (8/14 Pages) Maxim Integrated Products – 5-Output Power-Management IC For Low-Cost PDAs

5-Output Power-Management IC For
Low-Cost PDAs
Pin Description
PIN
FUNCTION
1
COR1 1V, 250mA LDO Output for CPU Core. COR1 turns off when V_IN < 3V or MAIN < 3.1V.
2
IN
Input Voltage to the Device. Bypass to GND with a 1µF capacitor.
3.3V, 400mA LDO Output for Secure Digital Card Slot. SDIG has reverse current protection so SDIG
3
SDIG can be biased when no power is present at IN. SDIG output turns off when V_IN < 3V or when ENSD
goes low.
4
ENSD
SDIG Enable Input. Drive ENSD low to turn off SDIG and high to turn on. SDIG cannot be activated
when V_IN < 3V.
5
REF
1.25V Reference. Bypass with 0.1µF to GND.
6
RS
Reset Output. RS is an active-low, open-drain output that goes low when V_MAIN falls below 3.1V. RS
deasserts when V_MAIN goes above 3.2V. Connect a 1MΩ pullup resistor from RS to MAIN.
7
N.C.
Not Connected
8
GND
Ground
9
LX
LCD Boost Switch. Connect to a boost inductor and Schottky diode. See Figure 1.
10
SW
LCD True Shutdown Switch Output. SW is the power source for the boost inductor. SW turns on when
ENLCD is high. For best efficiency, bypass SW with 4.7µF to GND.
11
SWIN
LCD True Shutdown Switch Input. The SWIN-to-SW switch turns off when ENLCD goes low or when
V_IN < 3V. Connect SWIN to IN.
12
LFB
LCD Feedback Input. Connect LFB to a resistor-divider network between the LCD output and GND.
The feedback threshold is 1.25V.
13
ENLCD ^{Enable Input for LCD (Boost Regulator). Drive ENLCD high to activate the LCD boost. Drive ENLCD}
low to shut down the LCD output. The LCD cannot be activated when V_IN < 3V.
14
ENC2
Enable Input for Secondary Core LDO (COR2). Drive ENC2 high to turn on COR2 and low to turn off.
COR2 cannot be activated when V_IN < 3V.
15
COR2 1.8V, 30mA LDO Output for Secondary Core. COR2 turns off when V_IN < 3V or when ENC2 goes low.
16
MAIN 3.3V, 500mA LDO Output for Main Supply. MAIN output turns off when V_IN < 3V.
Detailed Description
Linear Regulators
The MAX1559 contains all power blocks and voltage
monitors for a small PDA. Power for logic and other
subsystems are provided by four LDOs:
• MAIN—Provides 3.3V at a guaranteed 500mA with a
typical current limit of 900mA.
• SDIG—Provides 3.3V at a guaranteed 400mA for
secure digital cards with a typical current limit
of 630mA.
• COR1—1V for CPU core guarantees 250mA and a
typical current limit of 450mA.
• COR2—1.8V for CODEC core guarantees 30mA and
a typical current limit of 50mA.
Note that it may not be possible to draw the rated cur-
rent of MAIN and SDIG at all operating input voltages
due to the dropout limitations of those regulators. The
typical dropout resistance of the MAIN regulator is 0.7Ω
(350mV drop at 500mA), and the typical dropout resis-
tance of the SDIG regulator is 0.85Ω (340mV drop at
400mA).
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