MAX1534 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers

19-2662; Rev 0; 10/02
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
General Description
The MAX1534 is a high-efficiency, triple-output power
supply for keep-alive (always on) voltage rails. The
500mA buck regulator with an internal current-limited
0.5Ω PMOS steps down the battery or wall adapter
supply rail to a fixed 5V or an adjustable output voltage.
Two integrated low-voltage linear regulators follow this
output and provide two independent preset output volt-
ages of 3.3V and 1.8V, or adjustable output voltages.
The buck regulator utilizes a peak current-limit, pulse-
frequency modulation (PFM) architecture for highest
light-load efficiency to conserve battery life. High
switching frequencies (up to 200kHz) allow the use of
tiny surface-mount inductors and output capacitors.
Operation to 100% duty cycle minimizes dropout volt-
age (250mV at 500mA).
The low-dropout linear regulators use an internal
P-channel metal-oxide (PMOS) pass transistor to mini-
mize supply current and deliver up to 160mA each of
continuous current.
The MAX1534 includes a power-OK (POK) signal that
indicates all outputs are in regulation. The 4% accurate
threshold of the SHDN input permits its use as a low-
battery detector.
The MAX1534 is available in a small 16-pin thin QFN
(4mm ✕ 4mm) package, occupying 33% less board
space than discrete solutions.
Applications
Notebook and Sub-
Notebook Computers
Wake-On LAN
2 to 4 Li+ Cells Battery-
Powered Devices
Hand-Held Devices
Keep-Alive Supplies
Standby Supplies
Features
o One Switching and Two Linear Regulators
o Switching Regulator
+4.5V to +24V Input Voltage Range
Over 95% Efficiency
Up to 500mA Output Current
Up to 200kHz Switching Frequency
Fixed 5V or Adjustable Output Voltage
Internal 0.5Ω PMOS Switch
100% Maximum Duty Cycle for Low-Dropout
Operation
o Two Low-Dropout Linear Regulators
Up to 160mA Output Current (Each)
3.3V/Adj Output Voltage for OUT1
1.8V/Adj Output Voltage for OUT2
o ±1.5% Accurate Output Voltage
o ±4% Accurate Shutdown for Low Battery
Detection
o Thermal Shutdown Protection
o POK Output
o 1mW Typical Standby Power
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX1534ETE -40°C to +85°C 16 Thin QFN (4mm × 4mm)
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
V_OUT1 = +3.3V ALWAYS
V_OUT2 = +1.8V ALWAYS
POK ^SHDN
BP
IN
FB3
PRESET
ILIM
FB1
LX
MAX1534
FB2
OUT1
OUT2
LDOIN
GND
V_IN = +7V TO +24V
V_OUT3 = +5V ALWAYS
________________________________________________________________ Maxim Integrated Products 1
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