MAXIM MAX1953, MAX1954, MAX1957 Technical data
General Description
The MAX1953/MAX1954/MAX1957 is a family of versatile, economical, synchronous current-mode, pulse-width
modulation (PWM) buck controllers. These step-down
controllers are targeted for applications where cost and
size are critical.
The MAX1953 operates at a fixed 1MHz switching frequency, thus significantly reducing external component
size and cost. Additionally, excellent transient response
is obtained using less output capacitance. The MAX1953
operates from low 3V to 5.5V input voltage and can supply up to 10A of output current. Selectable current limit is
provided to tailor to the external MOSFETs’ on-resistance
for optimum cost and performance. The output voltage is
adjustable from 0.8V to 0.86VIN.
With the MAX1954, the drain-voltage range on the highside FET is 3V to 13.2V and is independent of the supply
voltage. It operates at a fixed 300kHz switching frequency and can be used to provide up to 25A of output current with high efficiency. The output voltage is adjustable
from 0.8V to 0.86V
HSD
.
The MAX1957 features a tracking output voltage range of
0.4V to 0.86V
IN
and is capable of sourcing or sinking
current for applications such as DDR bus termination
and PowerPC™/ASIC/DSP core supplies. The MAX1957
operates from a 3V to 5.5V input voltage and at a fixed
300kHz switching frequency.
The MAX1953/MAX1954/MAX1957 provide a COMP pin
that can be pulled low to shut down the converter in
addition to providing compensation to the error amplifier.
An input undervoltage lockout (ULVO) is provided to
ensure proper operation under power-sag conditions to
prevent the external power MOSFETs from overheating.
Internal digital soft-start is included to reduce inrush current. The MAX1953/MAX1954/MAX1957 are available in
tiny 10-pin µMAX packages.
Applications
Printers and Scanners
Graphic Cards and Video Cards
PCs and Servers
Microprocessor Core Supply
Low-Voltage Distributed Power
Telecommunications and Networking
Features
♦ Low-Cost Current-Mode Controllers
♦ Fixed-Frequency PWM
♦ MAX1953
1MHz Switching Frequency
Small Component Size, Low Cost
Adjustable Current Limit
♦ MAX1954
3V to 13.2V Input Voltage
25A Output Current Capability
93% Efficiency
300kHz Switching Frequency
♦ MAX1957
Tracking 0.4V to 0.86V
IN
Output Voltage Range
Sinking and Sourcing Capability of 3A
♦ Shutdown Feature
♦ All N-Channel MOSFET Design for Low Cost
♦ No Current-Sense Resistor Needed
♦ Internal Digital
†
Soft-Start
♦ Thermal Overload Protection
♦ Small 10-Pin µMAX Package
MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-2373; Rev 0; 4/02
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.
Pin Configurations
Pin Configurations continued at end of data sheet.
†Patent Pending
PowerPC is a trademark of Motorola, Inc.
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-PACKAGE
MAX1953EUB -40°C to +85°C 10 µMAX
MAX1954EUB -40°C to +85°C 10 µMAX
MAX1957EUB -40°C to +85°C 10 µMAX
TOP VIEW
ILIM
COMP
1
2
MAX1953EUB
3
FB
4
5
µMAX
10
BST
9
LX
8
DH
7
PGNDGND
DLIN
6
MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
IN, FB to GND...........................................................-0.3V to +6V
LX to BST..................................................................-6V to +0.3V
BST to GND ............................................................-0.3V to +20V
DH to LX....................................................-0.3V to (V
BST
+ 0.3V)
DL, COMP to GND.......................................-0.3V to (V
IN
+ 0.3V)
HSD, ILIM, REFIN to GND ........................................-0.3V to 14V
PGND to GND .......................................................-0.3V to +0.3V
I
DH
, IDL................................................................±100mA (RMS)
Continuous Power Dissipation (T
A
= +70°C)
(derate 5.6mW/°C above +70°C)..................................444mW
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
ELECTRICAL CHARACTERISTICS
(VIN= 5V, V
BST
- VLX= 5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Operating Input Voltage Range 3.0 5.5 V
HSD Voltage Range MAX1954 only (Note 2) 3.0 13.2 V
Quiescent Supply Current V
Standby Supply Current (MAX1953/ MAX1957) V
Standby Supply Current (MAX1954)
= 1.5V, no switching 1 2 mA
FB
= V
IN
BST
V
= V
IN
BST
COMP = GND
Undervoltage Lockout Trip Level Rising and falling V
Output Voltage Adjust Range (V
ERROR AMPLIFIER
FB Regulation Voltage
) 0.8
OUT
T
= 0°C to +85°C (MAX1953/MAX1954) 0.788 0.8 0.812
A
T
= -40°C to +85°C (MAX1953/MAX1954) 0.776 0.8 0.812
A
MAX1957 only
Transconductance 70 110 160 µS
FB Input Leakage Current V
REFIN Input Bias Current V
= 0.9V 5 500 nA
FB
= 0.8V, MAX1957 only 5 500 nA
REFIN
FB Input Common-Mode Range -0.1 1.5 V
REFIN Input Common-Mode Range MAX1957 only -0.1 1.5 V
Current-Sense Amplifier Voltage Gain Low ILIM = GND (MAX1953 only) 5.67 6.3 6.93 V/V
V
= VIN or ILIM = open (MAX1953 only)
Current-Sense Amplifier Voltage Gain
ILIM
MAX1954/MAX1957
= 5.5V, COMP = GND 220 350 µA
= 5.5V, V
= 13.2V,
HSD
, 3% hysteresis 2.50 2.78 2.95 V
IN
220 350 µA
0.86 x
V
IN
V
REFIN
- 8mV
V
REFIN
V
REFIN
+ 8mV
3.15 3.5 3.85 V/V
V
V
MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 5V, V
BST
- VLX= 5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
Note 1: Specifications to -40°C are guaranteed by design and not production tested.
Note 2: HSD and IN are externally connected for applications where V
HSD
< 5.5V.
PARAMETER CONDITIONS MIN TYP MAX UNITS
ILIM Input Impedance MAX1953 only 50 125 200 kΩ
V
- VLX, ILIM = GND (MAX1953 only) 85 105 125
PGND
V
- VLX, ILIM = open (MAX1953 only) 190 210 235
Current-Limit Threshold
PGND
V
- VLX, ILIM = IN (MAX1953 only) 290 320 350
PGND
V
– VLX (MAX1954/MAX1957 only) 190 210 235
PGND
OSCILLATOR
Switching Frequency
MAX1953 0.8 1 1.2 MHz
MAX1954/MAX1957 240 300 360 kHz
Maximum Duty Cycle Measured at DH 86 89 96 %
Minimum Duty Cycle
MAX1953, measured at DH 15 18
MAX1954/MAX1957, measured at DH 4.5 5.5
SOFT-START
Soft-Start Period
MAX1953 4
MAX1954/MAX1957 3.4
FET DRIVERS
DH On-Resistance, High State 2 3 Ω
DH On-Resistance, Low State 1.5 3 Ω
DL On-Resistance, High State 2 3 Ω
DL On-Resistance, Low State 0.8 2 Ω
LX, BST Leakage Current
LX, BST, HSD Leakage Current
= 10.5V, V
BST
MAX1953/MAX1957
V
= 18.7V, V
BST
= 13.2V (MAX1954 only)
V
HSD
= V
LX
= 13.2V, V
LX
= 5.5V,
IN
IN
= 5.5V
20 µA
30 µA
V
THERMAL PROTECTION
Thermal Shutdown Rising temperature 160 °C
Thermal Shutdown Hysteresis 15 °C
SHUTDOWN CONTROL
COMP Logic Level Low 3V < V
COMP Logic Level High 3V < V
< 5.5V 0.25 V
IN
< 5.5V 0.8 V
IN
COMP Pullup Current 100 µA
mV
%
ms
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
4 _______________________________________________________________________________________
EFFICIENCY vs. LOAD CURRENT
MAX1953
100
VIN = 3.3V
95
90
85
80
75
70
EFFICIENCY (%)
65
60
55
50
0.1 10
VIN = 5V
V
OUT
CIRCUIT OF FIGURE 1
1
LOAD CURRENT (A)
= 2.5V
MAX1953 toc01
EFFICIENCY vs. LOAD CURRENT
MAX1954
100
V
= 2.5V
90
80
70
EFFICIENCY (%)
60
50
40
OUT
V
= 1.7V
OUT
VIN = 5V
CIRCUIT OF FIGURE 2
0.1 10
1
LOAD CURRENT (A)
MAX1953 toc02
EFFICIENCY vs. LOAD CURRENT
100
90
80
70
EFFICIENCY (%)
60
50
40
0.1 10
MAX1957
V
= 1.25V
OUT
VIN = 5V
CIRCUIT OF FIGURE 3
1
LOAD CURRENT (A)
MAX1953 toc03
EFFICIENCY vs. LOAD CURRENT
MAX1954
100
V
95
90
85
80
75
70
EFFICIENCY (%)
65
60
55
50
025
= 1.8V
OUT
VIN = 12V
CIRCUIT OF FIGURE 4
LOAD CURRENT (A)
MAX1953 toc04
2015105
MAX1954
OUTPUT VOLTAGE vs. LOAD CURRENT
2.60
2.55
2.50
2.45
OUTPUT VOLTAGE (V)
2.40
V
HSD
= VIN = 5V
MAX1953 toc06
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1953
2.60
2.55
VIN = 5V
2.50
VIN = 3.3V
OUTPUT VOLTAGE (V)
2.45
2.40
03.0
CIRCUIT OF FIGURE 1
LOAD CURRENT (A)
MAX1953 toc05
2.52.01.51.00.5
MAX1954
OUTPUT VOLTAGE vs. LOAD CURRENT
1.80
1.75
1.70
1.65
OUTPUT VOLTAGE (V)
1.60
V
HSD
= VIN = 5V
MAX1953 toc07
2.35
06
CIRCUIT OF FIGURE 2
54321
LOAD CURRENT (A)
1.55
06
CIRCUIT OF FIGURE 2
54321
LOAD CURRENT (A)
MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX1953
FREQUENCY vs. INPUT VOLTAGE
MAX1953 toc13
INPUT VOLTAGE (V)
FREQUENCY (MHz)
5.04.54.03.5
0.98
1.00
1.02
1.04
1.06
0.96
3.0 5.5
TA = -40°C
TA = +85°C
TA = +25°C
V
OUT
= 2.5V
MAX1954/MAX1957
FREQUENCY vs. INPUT VOLTAGE
MAX1953 toc14
INPUT VOLTAGE (V)
FREQUENCY (kHz)
5.04.54.03.5
275
280
285
290
295
300
305
310
315
320
270
3.0 5.5
TA = -40°C
TA = +25°C
TA = +85°C
V
OUT
= 1.25V
MAX1957
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1953 toc08
LOAD CURRENT (A)
OUTPUT VOLTAGE (V)
210-1-2
1.20
1.25
1.30
1.35
1.15
-3 3
VIN = 5V
CIRCUIT OF FIGURE 3
MAX1954
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1953 toc11
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.04.54.03.5
2.47
2.48
2.49
2.50
2.51
2.52
2.46
3.0 5.5
I
LOAD
= 0
I
LOAD
= 5A
CIRCUIT OF FIGURE 2
MAX1957
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1953 toc12
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.04.54.03.5
1.21
1.23
1.25
1.27
1.29
1.19
3.0 5.5
I
LOAD
= 0
I
LOAD
= 3A
CIRCUIT OF FIGURE 3
MAX1953
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1953 toc09
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.04.54.03.5
2.45
2.50
2.55
2.60
2.40
3.0 5.5
I
LOAD
= 3A
I
LOAD
= 0
CIRCUIT OF FIGURE 1
MAX1954
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1953 toc10
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.04.54.03.5
1.66
1.68
1.70
1.72
1.74
1.76
1.64
3.0 5.5
I
LOAD
= 0
I
LOAD
= 5A
CIRCUIT OF FIGURE 2
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
6 _______________________________________________________________________________________
MAX1954
LOAD TRANSIENT
400µs/div
MAX1953 toc16
100mV/div
5A
2.5A
V
OUT
AC-COUPLED
I
LOAD
MAX1953
LOAD TRANSIENT
CIRCUIT OF FIGURE 1
400µs/div
MAX1953 toc15
100mV/div
3A
1.5A
V
OUT
AC-COUPLED
I
LOAD
MAX1957
LOAD TRANSIENT
V
OUT
AC-COUPLED
I
LOAD
400µs/div
MAX1953 toc17
50mV/div
3A
-3A
NO-LOAD SWITCHING WAVEFORMS
MAX1953
I
LX
LX
DL
DH
2µs/div
MAX1953 toc18
2A/div
5V/div
5V/div
5V/div
MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
_______________________________________________________________________________________ 7
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX1953
FULL-LOAD SWITCHING WAVEFORMS
MAX1953 toc19
2µs/div
I
LX
LX
DL
DH
2A/div
5V/div
5V/div
5V/div
MAX1954/MAX1957
SHORT-CIRCUIT SWITCHING WAVEFORMS
MAX1953 toc23
4µs/div
I
LX
LX
DL
DH
5A/div
10V/div
5V/div
10V/div
MAX1954/MAX1957
FULL-LOAD SWITCHING WAVEFORMS
MAX1953 toc22
4µs/div
I
LX
LX
DL
DH
2A/div
10V/div
5V/div
10V/div
MAX1954/MAX1957
NO-LOAD SWITCHING WAVEFORMS
MAX1953 toc21
4µs/div
I
LX
LX
DL
DH
2A/div
10V/div
5V/div
10V/div
MAX1953
SHORT-CIRCUIT SWITCHING WAVEFORMS
MAX1953 toc20
2µs/div
I
LX
LX
DL
DH
5A/div
5V/div
5V/div
5V/div
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