19-1776; Rev 4; 8/09
KIT
ATION
EVALU
BLE
AVAILA
High-Voltage, Step-Down DC-DC
Controllers in µMAX
MAX1744/MAX1745
General Description
____________________________Features
♦
High-Voltage Operation (Up to 36V IN)
♦
Efficiency > 90%
♦
Output Power Capability Exceeds 50W
♦
10-Pin
µMax
Package
♦
Low-Dropout Voltage
♦
100% (max) Duty Cycle
♦
90µA Quiescent Current
♦
4µA Shutdown Current
♦
Up to 330kHz Switching Frequency
♦
Output Voltage
5V or 3.3V (MAX1744)
Adjustable 1.25V to 18V (MAX1745)
♦
Current-Limited Control Scheme
The MAX1744/MAX1745 are step-down DC-DC con-
trollers capable of handling up to 36V inputs. These
parts use a proprietary current-limited control scheme
for excellent light- and full-load efficiency, while their
330kHz (max) switching frequency permits small exter-
nal components for space-critical applications.
Operation to 100% duty cycle permits the lowest possi-
ble dropout voltage.
The MAX1744 contains an internal feedback network
that provides a pin-selectable output voltage of either
3.3V or 5V. The MAX1745 uses an external feedback
network to generate an adjustable output voltage
between 1.25V and 18V.
The MAX1744/MAX1745 are available in a space-sav-
ing 10-pin μMAX
®
package.
________________________Applications
Automotive Electronics
Telecom Systems
Wall-Cube-Powered Devices
Industrial Control Systems
Firewire
®
/IEEE
®
1394
Ordering Information
PART
MAX1744EUB+
MAX1744AUB+
MAX1744EUB/V+
MAX1745EUB+
TEMP RANGE
-40°C to +85°C
-40°C to +125°C
-40°C to +85°C
-40°C to +85°C
-40°C to +125°C
-40°C to +85°C
PIN-PACKAGE
10 μMAX
10 μMAX
10 μMAX
10 μMAX
10 μMAX
10 μMAX
μMAX is a registered trademark of Maxim Integrated Products, Inc.
Firewire is a registered trademark of Apple, Inc.
IEEE is a registered service mark of the Institute of Electrical
and Electronics Engineers, Inc.
MAX1745AUB+
MAX1745EUB/V+
+Denotes
a lead(Pb)-free/RoHS-compliant package.
/V Denotes an automotive qualified part.
Typical Operating Circuit
IN
4.5V TO 36V
Pin Configuration
TOP VIEW
+
IN
ON
5V
OFF
3.3V
SHDN
3/5
VL
REF
GND
VH
EXT
P
GND
1
VL
REF
2
3
4
5
10
IN
9
EXT
VH
SHDN
CS
MAX1744
MAX1745
8
7
6
MAX1744
CS
OUT
OUT
3.3V
OR 5V
3/5 (FB)
OUT
μMAX
( ) ARE FOR MAX1745 ONLY.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
High-Voltage, Step-Down DC-DC
Controllers in µMAX
MAX1744/MAX1745
ABSOLUTE MAXIMUM RATINGS
IN, EXT,
SHDN
to GND...........................................-0.3V to +38V
VH to GND..............................................................-0.3V to +34V
VH, EXT to IN............................................................-7V to +0.3V
CS, OUT to GND ....................................................-0.3V to +20V
FB, 3/5, REF to GND .....................................-0.3V to (VL + 0.3V)
VL to GND...................................................................-0.3V to 6V
Continuous Power Dissipation (T
A
= +70°C)
10-Pin μMAX (derate 5.6mW/°C above 70°C) .............444mW
Operating Temperature Range
MAX174_EUB ..................................................-40°C to +85°C
MAX174_AUB ................................................-40°C to +125°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
(VIN = V
SHDN
= 5.5V to 36V, 3/5 = GND, ILOAD = 0,
TA = 0°C to +85°C,
unless otherwise noted. Typical values at VIN = V
SHDN
=
36V, TA = +25°C.)
PARAMETER
Input Voltage Range
Supply Current into IN
Shutdown Supply Current
Output Voltage (MAX1744)
OUT Input Current (MAX1744)
FB Threshold Voltage (MAX1745)
FB Input Current (MAX1745)
VH Output Voltage with Respect to IN
VL Output Voltage
VL Undervoltage Lockout
CS Threshold Voltage
CS Input Current
SHDN,
3/5 Logic-High Threshold
SHDN,
3/5 Logic-Low Threshold
3/5 Input Current
SHDN
Input Current
EXT Resistance
Minimum EXT Off-Time
Minimum EXT On-Time
Output Line Regulation
Output Load Regulation
Reference Voltage
REF Load Regulation
REF Line Regulation
Figure 1, 5.5V < V
IN
< 36V, I
LOAD
= 1A
Figure 1, V
IN
= 12V, 30mA < I
LOAD
< 2A
I
REF
= 0
0
≤
I
REF
≤
100μA
V
IN
= 4.5V to 36V, I
REF
= 0
1.22
1.5
0.7
V
CS
= V
OUT
= 2.5V to 18V
V
CS
= V
OUT
= V
GND
V
CS
= V
OUT
= 2.5V to 18V
V
CS
= V
OUT
= V
GND
V
IN
= 4.5V to 36V
V
IN
= 4.5V to 36V
SHDN
= GND
3/5 = GND
V
SHDN
= 36V
8
2.0
1.0
5
15
1.25
4
30
1.28
10
60
V
IN
= 5.5V to 36V, I
VH
= 100μA to 20mA
V
IN
= 5.5V to 36V, I
VL
= 100μA to 2mA
V
SHDN
= V
IN
= 5.5V to 36V
SHDN
= GND
3/5 = VL
3/5 = GND
3/5 = VL, V
OUT
= 5V
Falling edge, hysteresis = 8mV
1.22
-50
-6.0
4.5
2.0
85
80
0
-25
2.4
0.4
±1
±1
12
20
2.5
1.5
-5.3
5.0
3.0
100
110
15
4.85
3.20
CONDITIONS
MIN
4.5
90
4
5.00
3.30
28
1.25
TYP
MAX
36
140
12
5.15
3.40
44
1.28
50
-4.3
5.5
4.1
115
150
25
0
UNITS
V
μA
μA
V
μA
V
nA
V
V
V
mV
μA
V
V
μA
μA
Ω
μs
μs
mV/V
mV/A
V
mV
μV/V
2
_______________________________________________________________________________________
High-Voltage, Step-Down DC-DC
Controllers in µMAX
MAX1744/MAX1745
ELECTRICAL CHARACTERISTICS
(VIN = V
SHDN
= 5.5V to 36V, 3/5 = GND, ILOAD = 0,
TA = -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
Input Voltage Range
Supply Current into IN
Shutdown Supply Current
Output Voltage (MAX1744)
OUT Input Current (MAX1744)
FB Threshold Voltage (MAX1745)
FB Input Current (MAX1745)
VH Output Voltage with Respect to IN
VL Output Voltage
VL Undervoltage Lockout
CS Threshold Voltage
CS Input Current
SHDN,
3/5 Logic-High Threshold
SHDN,
3/5 Logic-Low Threshold
3/5 Input Current
SHDN
Input Current
EXT Resistance
Minimum EXT Off-Time
Minimum EXT On-Time
Reference Voltage
REF Load Regulation
REF Line Regulation
I
REF
= 0
0
≤
I
REF
≤
100μA
V
IN
= 4.5V to 36V, I
REF
= 0
1.5
0.7
1.22
V
CS
= V
OUT
= 2.5V to 18V
V
CS
= V
OUT
= V
GND
V
CS
= V
OUT
= 2.5V to 18V
V
CS
= V
OUT
= V
GND
V
IN
= 4.5V to 36V
V
IN
= 4.5V to 36V
SHDN
= GND
3/5 = GND
V
SHDN
= 36V
V
IN
= 5.5V to 36V, I
VH
= 100μA to 20mA
V
IN
= 5.5V to 36V, I
VL
= 100μA to 2mA
V
SHDN
= V
IN
= 5.5V to 36V
SHDN
= GND
3/5 = VL
3/5 = GND
3/5 = VL, V
OUT
= 5V
Falling edge, hysteresis = 8mV
1.22
-50
-6.0V
4.5
2.0
85
80
0
-25
2.4
0.4
±1
±1
12
20
2.5
1.5
1.28
10
60
4.85
3.20
CONDITIONS
MIN
4.5
MAX
36
140
12
5.15
3.40
44
1.28
50
-4.3V
5.5
4.1
115
150
25
0
UNITS
V
μA
μA
V
μA
V
nA
V
V
V
mV
μA
V
V
μA
μA
Ω
μs
μs
V
mV
μV/V
_______________________________________________________________________________________
3
High-Voltage, Step-Down DC-DC
Controllers in µMAX
MAX1744/MAX1745
ELECTRICAL CHARACTERISTICS
(VIN = V
SHDN
= 5.5V to 36V, 3/5 = GND, ILOAD = 0,
TA = -40°C to +125°C,
unless otherwise noted.) (Note 1)
PARAMETER
Input Voltage Range
Supply Current into IN
Shutdown Supply Current
Output Voltage (MAX1744)
OUT Input Current (MAX1744)
FB Threshold Voltage (MAX1745)
FB Input Current (MAX1745)
VH Output Voltage with Respect to IN
VL Output Voltage
VL Undervoltage Lockout
CS Threshold Voltage
CS Input Current
SHDN,
3/5 Logic-High Threshold
SHDN,
3/5 Logic-Low Threshold
3/5 Input Current
SHDN
Input Current
EXT Resistance
Minimum EXT Off-Time
Minimum EXT On-Time
Reference Voltage
REF Load Regulation
REF Line Regulation
I
REF
= 0
0
≤
I
REF
≤
100μA
V
IN
= 4.5V to 36V, I
REF
= 0
1.5
0.7
1.22
V
CS
= V
OUT
= 2.5V to 18V
V
CS
= V
OUT
= V
GND
V
CS
= V
OUT
= 2.5V to 18V
V
CS
= V
OUT
= V
GND
V
IN
= 4.5V to 36V
V
IN
= 4.5V to 36V
SHDN
= GND
3/5 = GND
V
SHDN
= 36V
V
IN
= 5.5V to 36V, I
VH
= 100μA to 20mA
V
IN
= 5.5V to 36V, I
VL
= 100μA to 2mA
V
SHDN
= V
IN
= 5.5V to 36V
SHDN
= GND
3/5 = VL
3/5 = GND
3/5 = VL, V
OUT
= 5V
Falling edge, hysteresis = 8mV
1.22
-50
-6.0V
4.5
1.6
85
80
0
-25
2.4
0.4
±1
±1
12
20
2.5
1.5
1.28
10
80
4.85
3.20
CONDITIONS
MIN
4.5
MAX
36
140
15
5.15
3.40
44
1.28
50
-4.3V
5.5
4.1
115
150
25
0
UNITS
V
μA
μA
V
μA
V
nA
V
V
V
mV
μA
V
V
μA
μA
Ω
μs
μs
V
mV
μV/V
Note 1:
Specifications to -40°C are guaranteed by design, not production tested.
4
_______________________________________________________________________________________
High-Voltage, Step-Down DC-DC
Controllers in µMAX
Typical Operating Characteristics
(Circuit of Figure 1, T
A
= +25°C, unless otherwise specified.)
MAX1744/MAX1745
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= +3.3V)
MAX1744/5toc01
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= +5.0V)
B
A
80
EFFICIENCY (%)
C
60
D
MAX1744/5toc02
IN PIN QUIESCENT CURRENT
vs. INPUT VOLTAGE (5.5V TO 36V)
MAX1744/5toc03
100
B
A
80
EFFICIENCY (%)
C
D
100
110
105
QUIESCENT CURRENT (μA)
100
95
90
85
80
60
40
A: V
IN
= +5.5V
B: V
IN
= +12.0V
C: V
IN
= +24.0V
D: V
IN
= +36.0V
0.0001
0.001
0.01
0.1
1
10
40
A: V
IN
= +7.2V
B: V
IN
= +12.0V
C: V
IN
= +24.0V
D: V
IN
= +36.0V
0.0001
0.001
0.01
0.1
1
10
20
20
0
LOAD CURRENT (A)
0
LOAD CURRENT (A)
0
10
20
INPUT VOLTAGE (V)
30
40
IN PIN QUIESCENT CURRENT
vs. INPUT VOLTAGE (3.5V TO 5.5V)
MAX1744/5toc04
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
MAX1744/5toc05
IN PIN QUIESCENT CURRENT
vs. TEMPERATURE
94
QUIESCENT CURRENT (μA)
93
92
91
90
89
88
87
MAX1744/5toc06
6
5
QUIESCENT CURRENT (mA)
4
3
2
1
140
120
SWITCHING FREQUENCY (kHz)
100
80
60
40
20
V
OUT
= 3.3V
I
OUT
= 2.0A
0
10
20
INPUT VOLTAGE (V)
30
95
V
OUT
= 3.3V
0
3.5
4.5
INPUT VOLTAGE (V)
5.5
0
86
85
40
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
EXT RISE AND FALL TIMES
vs. CAPACITANCE
MAX1744/5toc07
EXT RISE AND FALL TIMES
vs. TEMPERATURE
MAX1744/5toc08
CURRENT-SENSE TRIP LEVEL
vs. TEMPERATURE
MAX1744/5toc09
120
V
IN
= +5V
100
t
RISE
AND t
FALL
(ns)
80
60
t
FALL
40
20
0
0
1000
2000
3000
4000
t
RISE
50
45
40
t
RISE
AND t
FALL
(ns)
35
30
25
20
15
10
5
0
t
FALL
V
IN
= +5V
C
L
= 1000pF
t
RISE
115
CURRENT-SENSE TRIP LEVEL (mV)
110
105
100
95
90
85
5000
-50
-25
0
25
50
75
100
125
-50
-25
0
25
50
75
100
125
CAPACITANCE (pF)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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