Document
MAX1744/MAX1745
19-1776; Rev 4; 8/09 EVAALVUAAILTAIOBNLEKIT
High-Voltage, Step-Down DC-DC Controllers in µMAX
General Description
The MAX1744/MAX1745 are step-down DC-DC controllers 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 external components for space-critical applications. Operation to 100% duty cycle permits the lowest possible 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-saving 10-pin μMAX® package.
________________________Applications
Automotive Electronics Telecom Systems Wall-Cube-Powered Devices Industrial Control Systems Firewire®/IEEE® 1394
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.
Typical Operating Circuit
____________________________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
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX1744EUB+
-40°C to +85°C
10 μMAX
MAX1744AUB+
-40°C to +125°C 10 μMAX
MAX1744EUB/V+ -40°C to +85°C
10 μMAX
MAX1745EUB+
-40°C to +85°C
10 μMAX
MAX1745AUB+
-40°C to +125°C 10 μMAX
MAX1745EUB/V+ -40°C to +85°C
10 μMAX
+Denotes a lead(Pb)-free/RoHS-compliant package. /V Denotes an automotive qualified part.
Pin Configuration
IN 4.5V TO 36V
TOP VIEW
ON IN VH EXT OFF SHDN
5V 3.3V 3/5
MAX1744
VL REF CS
GND OUT
P
OUT 3.3V OR 5V
+ GND 1
VL 2 REF 3 3/5 (FB) 4
MAX1744 MAX1745
OUT 5
( ) ARE FOR MAX1745 ONLY.
μMAX
10 IN 9 EXT 8 VH 7 SHDN 6 CS
________________________________________________________________ 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.
MAX1744/MAX1745
High-Voltage, Step-Down DC-DC Controllers in µMAX
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......................................