19-1919; Rev 3; 7/06
24V Internal Switch, 100% Duty Cycle,
Step-Down Converters
General Description
____________________________Features
♦ 4.5V to 24V Input Voltage Range
♦ Preset 3.3V or 5V Output
The MAX1836/MAX1837 high-efficiency step-down
converters provide a preset 3.3V or 5V output voltage
from supply voltages as high as 24V. Using external
feedback resistors, the output voltage may be adjusted
♦ Adjustable Output from 1.25V to V
IN
from 1.25V to V . An internal current-limited switching
IN
MOSFET delivers load currents up to 125mA
(MAX1836) or 250mA (MAX1837).
♦ Output Currents Up to 125mA (MAX1836) or
250mA (MAX1837)
The unique current-limited control scheme, operating
with duty cycles up to 100%, minimizes the dropout
voltage (120mV at 100mA). Additionally, this control
scheme reduces supply current under light loads to
12µA. High switching frequencies allow the use of tiny
surface-mount inductors and output capacitors.
♦ Efficiency Over 90%
♦ 12µA Quiescent Current
♦ 3µA Shutdown Current
♦ 100% Maximum Duty Cycle for Low Dropout
♦ Small 6-Pin SOT23 and TDFN Packages
The MAX1836/MAX1837 step-down converters with
internal switching MOSFETs are available in 6-pin
SOT23 and 3mm x 3mm TDFN packages, making them
ideal for low-cost, low-power, space-sensitive applica-
tions. For increased output drive capability, use the
MAX1776 step-down converter that uses an internal
24V switch to deliver up to 500mA. For even higher cur-
rents, use the MAX1626/ MAX1627 step-down con-
trollers that drive an external P-channel MOSFET to
deliver up to 20W.
Ordering Information
PIN-
PACKAGE
TOP
MARK
PART
TEMP RANGE
MAX1836ETT33-T
MAX1836ETT50-T
MAX1836EUT33-T
MAX1836EUT50-T
MAX1837ETT33-T
MAX1837ETT50-T
MAX1837EUT33-T
MAX1837EUT50-T
-40°C to +85°C 6 TDFN-EP*
-40°C to +85°C 6 TDFN-EP*
-40°C to +85°C 6 SOT23-6
-40°C to +85°C 6 SOT23-6
-40°C to +85°C 6 TDFN-EP*
-40°C to +85°C 6 TDFN-EP*
-40°C to +85°C 6 SOT23-6
-40°C to +85°C 6 SOT23-6
AJG
AJE
AANY
AANW
AJH
Applications
9V Battery Systems
Notebook Computers
AJF
AANZ
AANX
Distributed Power Systems
Backup Supplies
*EP = Exposed pad.
4mA to 20mA Loop Power Supplies
Industrial Control Supplies
Handheld Devices
Selector Guide appears at end of data sheet.
Pin Configurations
Typical Operating Circuit
OUTPUT
3.3V OR 5V
INPUT
4.5V TO 24V
TOP VIEW
IN
LX
SHDN
FB
GND
IN
1
2
3
6
5
4
OUT
SHDN
LX
FB
GND
IN
1
2
3
6
5
4
OUT
SHDN
LX
MAX1836
MAX1837
OUT
MAX1836
MAX1837
MAX1836
MAX1837
GND
FB
TDFN
SOT23
NOTE: HIGH-CURRENT PATHS SHOWN WITH BOLD LINES.
________________________________________________________________ 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.