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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

Features

♦ One Switching and Two Linear Regulators

♦ 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

♦ 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

♦ ±1.5% Accurate Output Voltage

♦ ±4% Accurate Shutdown for Low Battery

Detection

♦ Thermal Shutdown Protection

♦ POK Output

♦ 1mW Typical Standby Power

MAX1534

High-Efficiency, Triple-Output, Keep-Alive

Power Supply for Notebook Computers

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-2662; Rev 0; 10/02

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART

TEMP RANGE

PIN-PACKAGE

MAX1534ETE

-40°C to +85°C

16 Thin QFN (4mm × 4mm)

MAX1534

POK

PRESET

ILIM

OUT1

= +3.3V ALWAYS

OUT3

= +5V ALWAYS

= +7V TO +24V

OUT2

= +1.8V ALWAYS

FB1

FB2

OUT1

OUT2

LDOIN

FB3

SHDN

GND

Typical Operating Circuit

Notebook and Sub-

Notebook Computers

Wake-On LAN

2 to 4 Li+ Cells Battery-

Powered Devices

Hand-Held Devices

Keep-Alive Supplies

Standby Supplies

Pin Configuration appears at end of data sheet.

Summary of content (16 pages)

PAGE 1
9-2662; Rev 0; 10/02 High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers Features 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 voltages of 3.3V and 1.
PAGE 2
MAX1534 High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers ABSOLUTE MAXIMUM RATINGS IN, ILIM, PRESET, SHDN to GND...........................-0.3V to +25V FB1, FB2, FB3, LDOIN, BP to GND..........................-0.3V to +6V OUT1, OUT2, POK to GND ...................-0.3V to (VLDOIN + 0.3V) LX to GND.......................................................-2V to (VIN + 0.3V) OUT1, OUT2 Short Circuit to GND.............................Continuous Peak IN Current......................
PAGE 3
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers (Circuit of Figure 1, VIN = 12V, ILIM = GND, PRESET = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS OUT1 Voltage Accuracy (Preset Mode) VOUT1 PRESET = GND IOUT1 = 100µA to 160mA 3.20 3.30 3.37 V OUT2 Voltage Accuracy (Preset Mode) VOUT2 PRESET = GND IOUT2 = 100µA to 160mA 1.74 1.80 1.
PAGE 4
MAX1534 High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers ELECTRICAL CHARACTERISTICS (Circuit of Figure 1, VIN = 12V, ILIM = GND, PRESET = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 4) PARAMETER Input Voltage Range Input Undervoltage Lockout Threshold SYMBOL VIN VUVLO CONDITIONS MIN TYP MAX UNITS V VIN 4.5 24 VIN rising 3.6 4.4 VIN falling 3.5 4.3 PRESET = GND 4.85 5.15 V PRESET = IN 0.97 1.03 V 0.22 0.
PAGE 5
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers MAX1534 ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VIN = 12V, ILIM = GND, PRESET = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 4) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS INPUTS AND OUTPUTS SHDN Input Trip Level Rising trip level, 100mV hysteresis 0.96 1.04 V 0.5 V Low PRESET, ILIM Logic Levels High 2.
PAGE 6
Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = +12V, PRESET = GND, TA = +25°C, unless otherwise noted.) NO-LOAD SUPPLY CURRENT vs. VIN, CIRCUIT 1, ILIM = GND SWITCHING FREQUENCY vs.
PAGE 7
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers LDO DROPOUT VOLTAGE vs. LOAD CURRENT LDO DROPOUT VOLTAGE vs. VOUT1 100 DROPOUT VOLTAGE (mV) 80 70 60 50 40 30 20 MAX1534 toc13 90 DROPOUT VOLTAGE (mV) 120 MAX1534 toc12 100 80 60 40 20 IOUT1 = 80mA 10 0 0 0 10 20 30 40 50 60 70 80 2.5 2.6 2.7 2.8 2.9 3.0 3.1 IOUT1 (mA) VOUT1 (V) LDO PSRR vs. FREQUENCY LDO LOAD TRANSIENT 3.2 3.
PAGE 8
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers MAX1534 Pin Description PIN NAME FUNCTION Shutdown Control Input. Drive SHDN above 1V to start up, and below 0.9V to shut down. LX is high impedance in shut down, and supply current reduces to 3.5µA. Connect SHDN to IN for automatic startup. SHDN can be connected to IN through a resistive voltage-divider to implement a programmable undervoltage lockout. 1 SHDN 2 POK Open-Drain Power-OK (POK) Output.
PAGE 9
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers MAX1534 VIN = +7V TO +24V 10µF IN SHDN POK L1 BP COUT3 D1 0.01µF PRESET 100kΩ VOUT3 = +5V ALWAYS LX MAX1534 ILIM FB3 FB1 FB2 VOUT1 = +3.3V ALWAYS OUT1 VOUT3 = +5V ALWAYS LDOIN VOUT2 = +1.8V ALWAYS OUT2 2.2µF 2.2µF 2.2µF GND NOTE: SEE TABLE 1 FOR RECOMMENDED COMPONENT VALUES. SEE TABLE 2 FOR COMPONENT SUPPLIERS. Figure 1.
PAGE 10
MAX1534 High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers Table 1. Recommended Components CIRCUIT 1 Input voltage CIRCUIT 2 7V 24V 7V 24V Max frequency 73kHz 175kHz 71kHz 160kHz On-time 8.8µs 1µs 9µs 1µs Buck output 5V, 500mA 5V, 250mA IN GND L1 15µH, 57mΩ, 1.60A Sumida CDRH6D38R-150 33µH, 124mΩ, 1.10A Sumida CDRH6D38R-330 D1 1A, 30V Schottky Nihon EP10QY03 0.5A, 30V Schottky Nihon EP05Q03L 47µF, 6.3V, ceramic TDK C3225X5R0J476M 33µF, 6.
PAGE 11
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers MAX1534 IN 1V MAX1534 VL REG BP REF 0.01µF LX TSDN STARTUP VL IPEAK GND 1V PMOS DRIVER VL ZX VL ENABLE 1V SHDN FB3 POK OUT3_OK LDOIN OUT2_OK PRESET PRESET OUT1_OK 0.9V LDOIN PMOS DRIVER 1V 1V OUT2_OK PMOS DRIVER OUT1 OUT2 LDOIN 0.9V OUT1_OK FB1 FB2 0.9V PRESET PRESET PRESET PRESET Figure 2. MAX1534 Functional Block Diagram down, the supply current drops to 3.5µA, maximizing battery life.
PAGE 12
MAX1534 High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers ous operation, do not exceed the absolute maximum junction temperature rating of TJ = +150°C. Operating Region and Power Dissipation The MAX1534’s maximum power dissipation depends on the thermal resistance of the case and circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow.
PAGE 13
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers PRESET OUT1 VOUT3 50mV/div AC-COUPLED MAX1534 VOUT1 VIN = +7V TO +24V IN RTOP1 FB1 10V MAX1534 VLX 10V/div 0 RBOT1 VOUT3 LX RTOP3 VOUT2 1A OUT2 ILX 500mA/div FB3 RTOP2 RBOT3 0 FB2 4µs/div RBOT2 GND VIN = 12V, IOUT3 = 300mA Figure 3. Normal Buck Operation voltage. For optimum performance, select an inductor with the lowest possible DC resistance that fits in the allotted dimensions.
PAGE 14
MAX1534 High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers input capacitor that exhibits less than +10°C temperature rise at the RMS input current for optimal circuit longevity. Diode Selection The current in the external diode (D1 in Figure 1) changes abruptly from zero to its peak value each time the LX switch turns off. To avoid excessive losses, the diode must have a fast turn-on time and a low forward voltage.
PAGE 15
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers FB3 PRESET FB2 FB1 16 15 14 13 Chip Information TRANSISTOR COUNT: 1512 PROCESS: BiCMOS SHDN 1 12 BP POK 2 11 OUT1 GND 3 10 LDOIN ILIM 4 9 OUT2 MAX1534 5 6 7 8 LX IN IN LX 16 THIN QFN ______________________________________________________________________________________ 15 MAX1534 Pin Configuration
PAGE 16
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 24L QFN THIN.EPS MAX1534 High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers PACKAGE OUTLINE 12,16,20,24L QFN THIN, 4x4x0.8 mm 21-0139 A PACKAGE OUTLINE 12,16,20,24L QFN THIN, 4x4x0.