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.
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
MAX1534
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
PART
MAX1534ETE
Ordering Information
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C 16 Thin QFN (4mm
×
4mm)
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
V
IN
= +7V TO +24V
POK
BP
SHDN
IN
FB3
PRESET
ILIM
FB1
FB2
V
OUT1
= +3.3V ALWAYS
V
OUT2
= +1.8V ALWAYS
OUT1
OUT2
GND
LDOIN
LX
V
OUT3
= +5V ALWAYS
MAX1534
________________________________________________________________
Maxim Integrated Products
1
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.
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
MAX1534
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 (V
LDOIN
+ 0.3V)
LX to GND.......................................................-2V to (V
IN
+ 0.3V)
OUT1, OUT2 Short Circuit to GND.............................Continuous
Peak IN Current........................................................................2A
Maximum IN DC Current...................................................500mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin Thin QFN (derate 16.9mW/°C
above +70°C)............................................................1349mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= 12V, ILIM = GND,
PRESET
= GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
=
+25°C.)
PARAMETER
Input Voltage Range
Input Supply Current
Input Supply Current in
Dropout
Shutdown Supply Current
Input UVLO Threshold
BUCK REGULATOR
FB3 Voltage Accuracy (Preset
Mode) (Note 1)
FB3 Set Voltage (Adjustable
Mode) (Note 1)
FB3 Bias Current
LX Switch Minimum Off-Time
LX Switch Minimum On-Time
LX Switch Maximum On-Time
LX Switch On-Resistance
LX Current Limit
LX Zero-Crossing Threshold
LX Zero-Crossing Timeout
LX Switch Leakage Current
Dropout Voltage
Line Regulation
Load Regulation
LINEAR REGULATORS
LDOIN Input Voltage
LDOIN Undervoltage Lockout
V
LDOIN
V
UVLO(LDO)
V
LDOIN
rising, hysteresis = 40mV typ
2.5
2.15
5.5
2.4
V
V
LX does not rise above threshold
V
IN
= 24V, not
switching
T
A
= +25°C
T
A
= 0°C to +85°C
250
0.1
0.9
V
FB3
I
FB3
t
OFF(MIN)
t
ON(MIN)
t
ON(MAX)
R
LX
I
LX(PEAK)
V
IN
= 6V
V
IN
= 4.5V
ILIM = IN
ILIM = GND
800
425
-75
30
1
10
9
PRESET
= GND
PRESET
= IN
V
FB3
= 5.5V
0.22
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
4.92
4.90
0.985
0.98
5.00
5.00
1.00
1.00
3.5
0.42
0.50
10
0.5
0.6
1000
500
11
1.0
1.2
1200
575
+75
5.08
5.10
1.015
1.02
6.25
0.62
V
V
µA
µs
µs
µs
Ω
mA
mV
µs
µA
mV
%/V
%
V
UVLO
SYMBOL
V
IN
I
IN
I
IN(DROP)
No load, FB3 = 5.2V, LDOIN = GND
No load, FB3 = V
IN
= 4.5V, LDOIN = GND
SHDN
= GND
V
IN
rising
V
IN
falling
3.6
3.5
CONDITIONS
MIN
4.5
15
60
3.5
4.0
3.9
TYP
MAX
24
30
110
7
4.4
4.3
UNITS
V
µA
µA
µA
V
V
OUT3(DROPOUT)
I
LX(DC)
= 500mA
V
IN
= 8V to 24V, I
LX(DC)
= 200mA
I
LX(DC)
= 80mA to 400mA
2
_______________________________________________________________________________________
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, ILIM = GND,
PRESET
= GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
=
+25°C.)
PARAMETER
OUT1 Voltage Accuracy
(Preset Mode)
OUT2 Voltage Accuracy
(Preset Mode)
FB1, FB2 Set Voltage
(Adjustable Mode)
FB1, FB2 Bias Current
OUT1, OUT2 Adjustable Output
Voltage Range
Maximum OUT1 Output Current
OUT1 Current Limit
Maximum OUT2 Output Current
OUT2 Current Limit
LDOIN Current
LDO_ Dropout Voltage
LDO_ Line Regulation
FAULT DETECTION
POK Threshold
POK Propagation Delay
POK Output Low Voltage
POK Leakage Current
Thermal Shutdown Threshold
INPUTS AND OUTPUTS
SHDN
Input Trip Level
Input Leakage Current
PRESET,
ILIM Logic Levels
Rising trip level, 100mV hysteresis
V
SHDN
, V
PRESET
, V
ILIM
= 0 or 24V
Low
High
2.2
0.96
-1
1.0
1.04
+1
0.5
V
µA
V
V
OUT1, OUT2, and FB3 rising edge,
1% hysteresis (Note 3)
Falling edge, 50mV overdrive
I
SINK
= 1mA
High state, forced to 5.5V
Typical hysteresis = 15°C
+160
-13
-11
10
0.4
1
-9
%
µs
V
µA
°C
I
OUT1
= I
OUT2
= 0, V
LDOIN
= 5.5V
I
OUT_
= 80mA (Note 2)
V
LDOIN
= (V
OUT_
+ 0.4V) or
+2.5V to +5.5V, I
OUT_
= 1mA
-0.2
I
OUT2(MAX)
Continuous
V
OUT1
,
V
OUT2
I
OUT1(MAX)
SYMBOL
V
OUT1
V
OUT2
V
FB1
, V
FB2
CONDITIONS
PRESET
= GND
PRESET
= GND
PRESET
= IN
I
OUT1
= 100µA to
160mA
I
OUT2
= 100µA to
160mA
I
OUT_
= 100µA to
160mA
MIN
3.20
1.74
0.97
-25
1.0
160
160
160
160
165
120
0
550
265
240
+0.2
550
TYP
3.30
1.80
1.00
MAX
3.37
1.84
1.02
+25
V
LDOIN
UNITS
V
V
V
nA
V
mA
mA
mA
mA
µA
mV
%/V
MAX1534
PRESET
= IN, V
FB1
= V
FB2
= 1.1V
PRESET
= IN
Continuous
_______________________________________________________________________________________
3
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
MAX1534
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= 12V, ILIM = GND,
PRESET
= GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 4)
PARAMETER
Input Voltage Range
Input Undervoltage Lockout
Threshold
BUCK REGULATOR
FB3 Voltage Accuracy (Preset
Mode)
FB3 Set Voltage (Adjustable
Mode)
LX Switch Minimum Off-Time
LX Switch Maximum On-Time
LX Switch On-Resistance
LX Current Limit
LINEAR REGULATORS
LDOIN Input Voltage
LDOIN UVLO
OUT1 Voltage Accuracy (Preset
Mode)
OUT2 Voltage Accuracy (Preset
Mode)
FB1, FB2 Set Voltage (Adjustable
Mode)
OUT1, OUT2 Adjustable Output
Voltage Range
Maximum OUT1 Output Current
OUT1 Current Limit
Maximum OUT2 Output Current
OUT2 Current Limit
LDO_ Dropout Voltage
LDO_ Line Regulation
FAULT DETECTION
POK Threshold
OUT1, OUT2, and FB3 rising edge, 1%
hysteresis (Note 3)
-13
-8
%
I
OUT_
= 80mA (Note 2)
V
LDOIN
= (V
OUT_
+ 0.4V) or +2.5V
to +5.5V, I
OUT_
= 1mA
-0.2
I
OUT2(MAX)
Continuous
V
LDOIN
V
UVLO(LDO)
V
LDOIN
rising, hysteresis = 40mV (typ)
V
OUT1
V
OUT2
V
FB1
, V
FB2
V
OUT1
,
V
OUT2
I
OUT1(MAX)
PRESET
= GND
PRESET
= GND
PRESET
= IN
PRESET
= IN
Continuous
I
OUT1
= 100µA to
160mA
I
OUT2
= 100µA to
160mA
I
OUT_
= 100µA to
160mA
2.5
2.15
3.20
1.74
0.97
1.0
160
160
160
160
550
250
+0.2
550
5.5
2.40
3.40
1.86
1.03
V
LDOIN
V
V
V
V
V
V
mA
mA
mA
mA
mV
%/V
V
FB3
t
OFF(MIN)
t
ON(MAX)
R
LX
I
LX(PEAK)
V
IN
= 6V
V
IN
= 4.5V
ILIM = IN
ILIM = GND
800
425
PRESET
= GND
PRESET
= IN
4.85
0.97
0.22
8
5.15
1.03
0.62
12
1.0
1.2
1200
575
V
V
µs
µs
Ω
mA
SYMBOL
V
IN
V
UVLO
V
IN
V
IN
rising
V
IN
falling
CONDITIONS
MIN
4.5
3.6
3.5
TYP
MAX
24
4.4
4.3
UNITS
V
V
4
_______________________________________________________________________________________
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, ILIM = GND,
PRESET
= GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 4)
PARAMETER
INPUTS AND OUTPUTS
SHDN
Input Trip Level
PRESET,
ILIM Logic Levels
Rising trip level, 100mV hysteresis
Low
High
2.2
0.96
1.04
0.5
V
V
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1534
Note 1:
The output voltage at light loads has a DC regulation level higher than the error comparator threshold by half the ripple volt-
age.
Note 2:
The dropout voltage is defined as V
LDOIN
- V
OUT_
when V
LDOIN
= V
OUT_(NOM)
. Specification only applies when V
OUT_
≥
2.5V.
Note 3:
OUT1, OUT2 DC set point, FB3 set point at the DC trip threshold of buck regulator.
Note 4:
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= +12V,
PRESET
= GND, T
A
= +25°C, unless otherwise noted.)
BUCK OUTPUT VOLTAGE
vs. LOAD CURRENT, CIRCUIT 1
MAX1534 toc01
BUCK EFFICIENCY
vs. LOAD CURRENT, CIRCUIT 1
MAX1534 toc02
BUCK EFFICIENCY
vs. LOAD CURRENT, CIRCUIT 2
95
90
EFFICIENCY (%)
85
80
75
70
65
60
V
IN
= 20V
V
IN
= 12V
V
IN
= 7V
MAX1534 toc03
5.20
5.15
5.10
V
OUT3
(V)
5.05
5.00
4.95
4.90
4.85
ILIM = IN
4.80
0
V
IN
= 6V
(t
ON
LIMITED)
V
IN
= 20V
V
IN
= 12V
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0.1
100
V
IN
= 6V
V
IN
= 12V
V
IN
= 20V
ILIM = IN
1
10
I
OUT3
(mA)
100
1000
55
50
0.1
1
10
I
OUT3
(mA)
ILIM = GND
100
1000
50 100 150 200 250 300 350 400 450 500
I
OUT3
(mA)
BUCK EFFICIENCY vs. LOAD CURRENT
CIRCUIT 1, V
IN
= 12V
89
87
EFFICIENCY (%)
85
83
81
L = 10µH
79
77
ILIM = IN
75
0.1
1
10
I
OUT3
(mA)
100
1000
L = 15µH
MAX1534 toc04
SWITCHING FREQUENCY
vs. V
IN
, CIRCUIT 1, ILIM = IN
180
160
FREQUENCY (kHz)
140
120
100
80
60
40
20
0
6
10
14
V
IN
(V)
18
22
26
I
OUT3
= 100mA
I
OUT3
= 50mA
I
OUT3
= 10mA
I
OUT3
= 250mA
I
OUT3
= 500mA
MAX1534 toc05
200
L = 22µH
_______________________________________________________________________________________
5
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