19-2837; Rev 1; 11/04
KIT
ATION
EVALU
BLE
AVAILA
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
General Description
Features
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Up to 97% Efficiency
2MHz PWM Switching
800mA Guaranteed Output Current
Low 48µA Quiescent Current
Power-Saving Modes: Pulse-Group, Pulse-Skip,
Forced-PWM Mode
0.75V to 2.5V Preset Output Range
(in 50mV Increments)
Voltage-Positioning Load Transients
5mV
P-P
Output Ripple
Tiny 2.2µH Inductor
10µF Ceramic Output Capacitor
Low 0.1µA Shutdown Current
No External Schottky Diode Required
Soft-Start with Zero Inrush Current
170ms (min)
RESET
Output
Small 12-Pin, 4mm x 4mm Thin QFN Package
MAX1572
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 48µA (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.
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX1572ETC075
-40°C to +85°C
12 Thin QFN-EP**
MAX1572ETC130
-40°C to +85°C
12 Thin QFN-EP**
MAX1572ETC150
-40°C to +85°C
12 Thin QFN-EP**
MAX1572ETC180
-40°C to +85°C
12 Thin QFN-EP**
MAX1572ETC250
-40°C to +85°C
12 Thin QFN-EP**
MAX1572ETCxyz*
-40°C to +85°C
12 Thin QFN-EP**
*xyz
is for the output voltage (e.g., MAX1572ETC165 has a
1.65V output). Minimum order quantity is 2500.
**EP
= 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
Selector Guide appears at end of data sheet.
Typical Operating Circuit
INPUT
2.6V TO 5.5V
BATT
LX
2.2µH
OUTPUT
0.75V TO 2.5V
800mA
Pin Configuration
LX
8
TOP VIEW
9
EN1
10
11
12
1
RESET
PGND
7
6
EN2
GND
MAX1572
ABATT
PGND
GND
BATT
MAX1572
5
4
ABATT
MODE
SELECT
EN1
EN2
SS
GND
OUT
RESET
OUT
2
SS
3
GND
4mm x 4mm
THIN QFN
________________________________________________________________
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.
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
MAX1572
ABSOLUTE MAXIMUM RATINGS
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 +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
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.
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
(V
BATT
= 3.6V,
T
A
= +0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
BATT Input Voltage
Undervoltage Lockout Threshold
Quiescent Supply Current
Shutdown Supply Current
Maximum Output Current
OUT Bias Current
No load, EN1 = EN2 = BATT
100mA load
Output-Voltage Accuracy
(Voltage Positioning)
300mA load
550mA load
800mA load
Line Regulation
P-Channel On-Resistance
N-Channel On-Resistance
P-Channel Current-Limit Threshold
N-Channel Current-Limit Threshold
N-Channel Zero-Crossing Threshold
LX Output Current
LX Leakage Current
Maximum Duty Cycle
Minimum Duty Cycle
Switching Frequency
SS Output Impedance
EN1 = BATT, EN2 = GND or
EN1 = GND, EN2 = BATT
EN1 = EN2 = BATT
1.8
65
EN1 = EN2 = BATT
EN1 = BATT, EN2 = GND
(Note 2)
EN1 = EN2 = GND
100
0
16.7
2
100
17.3
2.2
150
MHz
kΩ
0.1
I
LX
= 180mA
I
LX
= 180mA
V
BATT
= 3.6V
V
BATT
= 2.6V
V
BATT
= 3.6V
V
BATT
= 2.6V
1.00
-0.68
15
-0.4
V
BATT
rising and falling, 1% hysteresis
EN1 = GND, EN2 = BATT, no switching
EN1 = BATT, EN2 = GND, no switching
EN1 = EN2 = GND, T
A
= +25°C
800
6
1.2
+0.8
0
-1
-2
0.3
0.28
0.33
0.18
0.20
1.25
-0.52
40
1.65
-0.37
65
1.4
10
0.30
0.45
%/V
Ω
Ω
A
A
mA
A
RMS
µA
%
%
9
2.7
+2.0
%
CONDITIONS
MIN
2.6
2.20
2.35
48
700
0.1
1
TYP
MAX
5.5
2.55
80
UNITS
V
V
µA
µA
mA
µA
2
_______________________________________________________________________________________
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 3.6V,
T
A
= +0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SS Discharge Resistance
EN_ Logic Input High
EN_ Logic Input Low
EN_ Logic Input Current
RESET
Threshold
RESET
Timer Delay Time
RESET
Output Low Level
RESET
Internal Pullup Resistance to OUT
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
T
J
rising
Percent of nominal, measured at OUT
From V
OUT
> 90% to
RESET
= HI
I
SINK
= 1mA
9
87
170
0.1
90
200
0.015
14
160
20
CONDITIONS
EN1 = EN2 = GND
V
ABATT
> 4.2V
V
ABATT
≤
4.2V
1.6
1.4
0.4
1
93
230
0.075
20
MIN
TYP
100
MAX
200
UNITS
Ω
V
V
µA
%
ms
V
kΩ
°C
°C
MAX1572
ELECTRICAL CHARACTERISTICS
(V
BATT
= 3.6V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 3)
PARAMETER
BATT Input Voltage
Undervoltage Lockout Threshold
Quiescent Supply Current
Shutdown Supply Current
Maximum Output Current
OUT Bias Current
Output-Voltage Accuracy
(Voltage Positioning)
P-Channel On-Resistance
N-Channel On-Resistance
N-Channel Current-Limit Threshold
N-Channel Zero-Crossing Threshold
LX Output Current
LX Leakage Current
Maximum Duty Cycle
Minimum Duty Cycle
Switching Frequency
SS Output Impedance
SS Discharge Resistance
EN_ Logic Input High
EN1 = EN2 = GND
V
ABATT
> 4.2V
V
ABATT
≤
4.2V
1.6
1.4
EN1 = EN2 = BATT
1.8
65
No load, EN1 = EN2 = BATT
100mA load
I
LX
= 180mA
I
LX
= 180mA
EN1 = EN2 = BATT
EN1 = BATT, EN2 = GND
(Note 2)
EN1 = EN2 = GND
100
17.3
2.2
150
200
-0.68
10
-1.2
V
BATT
rising and falling, 1% hysteresis
EN1 = GND, EN2 = BATT, no switching
EN1 = EN2 = GND
800
9
3.2
+2.8
0.45
0.3
-0.22
65
1.4
10
CONDITIONS
MIN
2.6
2.20
TYP
MAX
5.5
2.55
80
3
UNITS
V
V
µA
µA
mA
µA
%
Ω
Ω
A
mA
A
RMS
µA
%
%
MHz
kΩ
Ω
V
_______________________________________________________________________________________
3
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
MAX1572
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 3.6V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
EN_ Logic Input Low
EN_ Logic Input Current
RESET
Threshold
RESET
Timer Delay Time
RESET
Output Low Level
RESET
Internal Pullup Resistance to OUT
Percent of nominal, measured at OUT
From V
OUT
> 90% to
RESET
= HI
I
SINK
= 1mA
9
87
170
CONDITIONS
MIN
TYP
MAX
0.4
1
93
230
0.2
20
UNITS
V
µA
%
ms
V
kΩ
Note 2:
Guaranteed by design, not production tested.
Note 3:
Specifications to -40°C are guaranteed by design and not production tested.
Typical Operating Characteristics
(V
BATT
= 3.6V, V
OUT
= 1.5V, EN1 = GND, EN2 = BATT, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
WITH 2.5V OUTPUT
MAX1572toc01
EFFICIENCY vs. LOAD CURRENT
WITH 1.8V OUTPUT
MAX1572toc02
EFFICIENCY vs. LOAD CURRENT
WITH 1.5V OUTPUT
MAX1572toc03
100
90
EFFICIENCY (%)
80
70
60
50
40
1
10
100
100
90
EFFICIENCY (%)
80
70
60
50
40
V
IN
= 2.6V
V
IN
= 3.6V
V
IN
= 5V
100
90
EFFICIENCY (%)
80
70
60
50
40
V
IN
= 2.6V
V
IN
= 3.6V
V
IN
= 5V
V
IN
= 2.6V
V
IN
= 3.6V
V
IN
= 5V
1000
1
10
100
1000
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
vs. MODE
PULSE-
GROUP MODE
MAX1572toc04
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1572toc05
OUTPUT VOLTAGE vs. INPUT VOLTAGE
WITH 100mA LOAD
MAX1572toc06
100
90
EFFICIENCY (%)
80
70
60
50
40
1
10
100
PULSE-
SKIP MODE
FORCED-
PWM MODE
1.58
1.56
1.54
OUTPUT VOLTAGE (V)
1.52
1.50
1.48
1.46
1.44
1.42
1.40
T
A
= +25°C
T
A
= -40°C
T
A
= +85°C
1.55
1.53
OUTPUT VOLTAGE (V)
T
A
= +85°C
1.51
T
A
= -40°C
T
A
= +25°C
1.49
1.47
1.45
0
200
400
600
800
2.5
3.0
3.5
4.0
4.5
5.0
5.5
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
1000
LOAD CURRENT (mA)
4
_______________________________________________________________________________________
800mA, 2MHz, PWM DC-to-DC
Step-Down Converter with
RESET
MAX1572
Typical Operating Characteristics (continued)
(V
BATT
= 3.6V, V
OUT
= 1.5V, EN1 = GND, EN2 = BATT, T
A
= +25°C, unless otherwise noted.)
INPUT CURRENT vs. INPUT VOLTAGE
WITH NO LOAD
MAX1572toc07
HEAVY-LOAD SWITCHING WAVEFORMS
MAX1572 toc08
60
50
INPUT CURRENT (µA)
40
30
20
V
LX
2V/div
V
OUT
RIPPLE
10mV/div
I
L
10
I
LOAD
= 500mA
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
200ns/div
INPUT VOLTAGE (V)
500mA/div
LIGHT-LOAD SWITCHING WAVEFORMS
MAX1572 toc09
SOFT-START/SHUTDOWN WAVEFORMS
MAX1572 toc10
V
LX
2V/div
V
EN2
2V/div
V
OUT
V
OUT
RIPPLE
20mV/div
1V/div
I
L
I
LOAD
= 20mA
2µs/div
I
IN
500mA/div
100mA/div
200µs/div
RESET WAVEFORM
MAX1572 toc11
LOAD TRANSIENT, FORCED-PWM MODE
MAX1572 toc12
V
EN2
2V/div
V
OUT
100mV/div
V
OUT
1V/div
V
RESET
I
IN
100ms/div
1V/div
I
LOAD
I
LOAD
= 20mA TO 550mA
4µs/div
500mA/div
100mA/div
_______________________________________________________________________________________
5
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