www.docs.chipfind.ru
General Description
The MAX1572 is a fixed-frequency, synchronous step-
down DC-to-DC converter to power low-voltage micro-
processor/DSP cores in portable equipment requiring
high efficiency in a limited PC board area. The features
are optimized for high efficiency over a wide load range,
small external component size, low output ripple, and
excellent transient response. The input supply voltage
range is from 2.6V to 5.5V, while the output is internally
fixed from 0.75V to 2.5V in 50mV increments with a
guaranteed output current of 800mA. The high 2MHz
switching allows tiny low-cost capacitors and a low-pro-
file inductor, while the power-saving pulse-group mode
reduces quiescent current to 48A (typ) with light loads.
To reduce noise and RF interference, the converter can
be configured to provide forced-PWM operation.
The MAX1572 includes a low on-resistance internal
MOSFET switch and synchronous rectifier to maximize
efficiency and minimize external component count. No
external diode is needed. Other features include soft-
start to eliminate inrush current at startup and a 170ms
(min) RESET output to provide power-on/undervoltage
reset. The MAX1572 is available in a 12-pin, 4mm x
4mm thin QFN package with exposed paddle.
Applications
Cell Phones and Smart Phones
PDAs, Palmtops, and Notebook Computers
MP3 and DVD Players
Digital Cameras and Camcorders
PCMCIA Cards
Hand-Held Instruments
Features
o Up to 97% Efficiency
o 2MHz PWM Switching
o 800mA Guaranteed Output Current
o Low 48A Quiescent Current
o Power-Saving Modes: Pulse-Group, Pulse-Skip,
Forced-PWM Mode
o 0.75V to 2.5V Preset Output Range
(in 50mV Increments)
o Voltage-Positioning Load Transients
o 5mV
P-P
Output Ripple
o Tiny 2.2H Inductor
o 10F Ceramic Output Capacitor
o Low 0.1A Shutdown Current
o No External Schottky Diode Required
o Soft-Start with Zero Inrush Current
o 170ms (min) RESET Output
o Small 12-Pin, 4mm x 4mm Thin QFN Package
MAX1572
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
________________________________________________________________ Maxim Integrated Products
1
MAX1572
12
11
10
7
8
9
PGND
LX
BATT
3
2
1
GND
SS
RESET
4
5
6
EN1
GND
ABATT
EN2
GND
OUT
4mm x 4mm
THIN QFN
TOP VIEW
Pin Configuration
Ordering Information
LX
2.2
H
PGND
OUT
RESET
GND
ABATT
EN1
BATT
MODE
SELECT
INPUT
2.6V TO 5.5V
OUTPUT
0.75V TO 2.5V
800mA
EN2
SS
MAX1572
Typical Operating Circuit
19-2837; Rev 0; 4/03
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.
*xyz is for the output voltage (e.g., MAX1572ETC165 has a
1.65V output). Minimum order quantity is 2500.
**EP = Exposed paddle.
EVALUATION KIT
AVAILABLE
PART
TEMP RANGE
PIN-PACKAGE
MAX1572ETC075
-40
C to +85C
12 Thin QFN-EP**
MAX1572ETC130
-40
C to +85C
12 Thin QFN-EP**
MAX1572ETC150
-40
C to +85C
12 Thin QFN-EP**
MAX1572ETC180
-40
C to +85C
12 Thin QFN-EP**
MAX1572ETC250
-40
C to +85C
12 Thin QFN-EP**
MAX1572ETCxyz*
-40
C to +85C
12 Thin QFN-EP**
Selector Guide appears at end of data sheet.
MAX1572
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
BATT
= 3.6V, T
A
= +0C to +85C, unless otherwise noted. Typical values are at T
A
= +25C.)
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.
ABATT, BATT, EN1, EN2, RESET, OUT,
SS to GND ............................................................-0.3V to +6V
PGND to GND .......................................................-0.3V to +0.3V
LX Current (Note 1) .............................................................
2.1A
Output Short-Circuit Duration ............................................Infinite
Continuous Power Dissipation (T
A
= +70
C)
12-Pin Thin QFN (derate 16.9mW/
C above +70C)...1349mW
Operating Temperature Range ...........................-40
C to +85C
Junction Temperature ......................................................+150
C
Storage Temperature Range .............................-65
C to +150C
Lead Temperature (soldering, 10s) .................................+300
C
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
BATT Input Voltage
2.6
5.5
V
Undervoltage Lockout Threshold
V
BATT
rising and falling, 1% hysteresis
2.20
2.35
2.55
V
EN1 = GND, EN2 = BATT, no switching
48
80
Quiescent Supply Current
EN1 = BATT, EN2 = GND, no switching
700
A
Shutdown Supply Current
EN1 = EN2 = GND, T
A
= +25C
0.1
1
A
Maximum Output Current
800
mA
OUT Bias Current
6
9
A
No load, EN1 = EN2 = BATT
1.2
3.2
100mA load
-0.4
+0.8
+2.0
300mA load
0
550mA load
-1
Output-Voltage Accuracy
(Voltage Positioning)
800mA load
-2
%
Line Regulation
0.3
%/V
V
BATT
= 3.6V
0.28
0.45
P-Channel On-Resistance
I
LX
= 180mA
V
BATT
= 2.6V
0.33
V
BATT
= 3.6V
0.18
0.30
N-Channel On-Resistance
I
LX
= 180mA
V
BATT
= 2.6V
0.20
P-Channel Current-Limit Threshold
1.00
1.25
1.65
A
N-Channel Current-Limit Threshold
EN1 = EN2 = BATT
-0.68
-0.52
-0.37
A
N-Channel Zero-Crossing Threshold
EN1 = BATT, EN2 = GND
15
40
65
mA
LX Output Current
(Note 2)
1.4
A
RMS
LX Leakage Current
EN1 = EN2 = GND
0.1
10
A
Maximum Duty Cycle
100
%
EN1 = BATT, EN2 = GND or
EN1 = GND, EN2 = BATT
0
Minimum Duty Cycle
EN1 = EN2 = BATT
16.7
17.3
%
Switching Frequency
1.8
2
2.2
MHz
SS Output Impedance
65
100
150
k
Note 1: LX has internal clamp diodes to PGND and BATT. Applications that forward bias these diodes should take care not to
exceed the IC's package power dissipation limits.
MAX1572
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 3.6V, T
A
= +0C to +85C, unless otherwise noted. Typical values are at T
A
= +25C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SS Discharge Resistance
EN1 = EN2 = GND
100
200
V
ABATT
> 4.2V
1.6
EN_ Logic Input High
V
ABATT
4.2V
1.4
V
EN_ Logic Input Low
0.4
V
EN_ Logic Input Current
0.1
1
A
RESET Threshold
Percent of nominal, measured at OUT
87
90
93
%
RESET Timer Delay Time
From V
OUT
> 90% to RESET = HI
170
200
230
ms
RESET Output Low Level
I
SINK
= 1mA
0.015
0.075
V
RESET Internal Pullup Resistance to OUT
9
14
20
k
Thermal-Shutdown Threshold
T
J
rising
160
C
Thermal-Shutdown Hysteresis
20
C
ELECTRICAL CHARACTERISTICS
(V
BATT
= 3.6V, T
A
= -40C to +85C, unless otherwise noted.) (Note 3)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
BATT Input Voltage
2.6
5.5
V
Undervoltage Lockout Threshold
V
BATT
rising and falling, 1% hysteresis
2.20
2.55
V
Quiescent Supply Current
EN1 = GND, EN2 = BATT, no switching
80
A
Shutdown Supply Current
EN1 = EN2 = GND
3
A
Maximum Output Current
800
mA
OUT Bias Current
9
A
No load, EN1 = EN2 = BATT
3.2
Output-Voltage Accuracy
(Voltage Positioning)
100mA load
-1.2
+2.8
%
P-Channel On-Resistance
I
LX
= 180mA
0.45
N-Channel On-Resistance
I
LX
= 180mA
0.3
N-Channel Current-Limit Threshold
EN1 = EN2 = BATT
-0.68
-0.22
A
N-Channel Zero-Crossing Threshold
EN1 = BATT, EN2 = GND
10
65
mA
LX Output Current
(Note 2)
1.4
A
RMS
LX Leakage Current
EN1 = EN2 = GND
10
A
Maximum Duty Cycle
100
%
Minimum Duty Cycle
EN1 = EN2 = BATT
17.3
%
Switching Frequency
1.8
2.2
MHz
SS Output Impedance
65
150
k
SS Discharge Resistance
EN1 = EN2 = GND
200
V
ABATT
> 4.2V
1.6
EN_ Logic Input High
V
ABATT
4.2V
1.4
V
MAX1572
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
4
_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 3.6V, T
A
= -40C to +85C, unless otherwise noted.) (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
EN_ Logic Input Low
0.4
V
EN_ Logic Input Current
1
A
RESET Threshold
Percent of nominal, measured at OUT
87
93
%
RESET Timer Delay Time
From V
OUT
> 90% to RESET = HI
170
230
ms
RESET Output Low Level
I
SINK
= 1mA
0.2
V
RESET Internal Pullup Resistance to OUT
9
20
k
Note 2: Guaranteed by design, not production tested.
Note 3: Specifications to -40C are guaranteed by design and not production tested.
100
90
40
1
1000
EFFICIENCY vs. LOAD CURRENT
WITH 2.5V OUTPUT
60
50
80
70
MAX1572toc01
LOAD CURRENT (mA)
EFFICIENCY (%)
10
100
V
IN
= 2.6V
V
IN
= 3.6V
V
IN
= 5V
100
90
40
1
1000
EFFICIENCY vs. LOAD CURRENT
WITH 1.8V OUTPUT
60
50
80
70
MAX1572toc02
LOAD CURRENT (mA)
EFFICIENCY (%)
10
100
V
IN
= 2.6V
V
IN
= 3.6V
V
IN
= 5V
100
90
40
1
1000
EFFICIENCY vs. LOAD CURRENT
WITH 1.5V OUTPUT
60
50
80
70
MAX1572toc03
LOAD CURRENT (mA)
EFFICIENCY (%)
10
100
V
IN
= 2.6V
V
IN
= 3.6V
V
IN
= 5V
100
90
40
1
1000
EFFICIENCY vs. LOAD CURRENT
vs. MODE
60
50
80
70
MAX1572toc04
LOAD CURRENT (mA)
EFFICIENCY (%)
10
100
FORCED-
PWM MODE
PULSE-
SKIP MODE
PULSE-
GROUP MODE
1.58
1.56
1.40
0
800
OUTPUT VOLTAGE
vs. LOAD CURRENT
1.48
1.46
1.44
1.42
1.54
1.50
1.52
MAX1572toc05
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
200
400
600
T
A
= +85
C
T
A
= +25
C
T
A
= -40
C
1.55
1.45
2.5
5.5
OUTPUT VOLTAGE vs. INPUT VOLTAGE
WITH 100mA LOAD
1.49
1.47
1.53
1.51
MAX1572toc06
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.0
3.5
4.5
5.0
4.0
T
A
= +85
C
T
A
= +25
C
T
A
= -40
C
Typical Operating Characteristics
(V
BATT
= 3.6V, V
OUT
= 1.5V, EN1 = GND, EN2 = BATT, T
A
= +25C, unless otherwise noted.)
MAX1572
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
_______________________________________________________________________________________
5
60
0
2.0
5.5
INPUT CURRENT vs. INPUT VOLTAGE
WITH NO LOAD
30
10
20
50
40
MAX1572toc07
INPUT VOLTAGE (V)
INPUT CURRENT (
A)
2.5
3.0
4.0
4.5
5.0
3.5
HEAVY-LOAD SWITCHING WAVEFORMS
MAX1572 toc08
V
LX
I
L
V
OUT
RIPPLE
10mV/div
500mA/div
2V/div
200ns/div
I
LOAD
= 500mA
LIGHT-LOAD SWITCHING WAVEFORMS
MAX1572 toc09
V
LX
I
L
V
OUT
RIPPLE
20mV/div
500mA/div
2V/div
2
s/div
I
LOAD
= 20mA
SOFT-START/SHUTDOWN WAVEFORMS
MAX1572 toc10
V
EN2
I
IN
V
OUT
1V/div
100mA/div
2V/div
200
s/div
RESET WAVEFORM
MAX1572 toc11
V
EN2
I
IN
V
RESET
V
OUT
1V/div
1V/div
100mA/div
2V/div
100ms/div
LOAD TRANSIENT, FORCED-PWM MODE
MAX1572 toc12
I
LOAD
V
OUT
500mA/div
100mV/div
4
s/div
I
LOAD
= 20mA TO 550mA
Typical Operating Characteristics (continued)
(V
BATT
= 3.6V, V
OUT
= 1.5V, EN1 = GND, EN2 = BATT, T
A
= +25C, unless otherwise noted.)
PDF 
ZIP