Rainbow Electronics MAX1837 - Manual

General Description
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
from 1.25V to V
IN . An internal current-limited switching
MOSFET delivers load 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.
The MAX1836/MAX1837 step-down converters with
internal switching MOSFETs are available in a 6-pin
SOT23 package, making them ideal for low-cost, low-
power, space-sensitive applications. For increased out-
put drive capability, use the MAX1776 step-down
converter that uses an internal 24V switch to deliver up
to 500mA. For even higher currents, use the MAX1626/
MAX1627 step-down controllers that drive an external
P-channel MOSFET to deliver up to 20W.
________________________Applications
9V Battery Systems
Notebook Computers
Distributed Power Systems
Backup Supplies
4mA to 20mA Loop Power Supplies
Industrial Control Supplies
Hand-Held Devices
____________________________Features
♦ 4.5V to 24V Input Voltage Range
♦ Preset 3.3V or 5V Output
♦ Adjustable Output from 1.25V to V
IN
♦ Output Currents Up to 125mA (MAX1836) or
250mA (MAX1837)
♦ Internal P-Channel MOSFET
♦ Efficiency Over 90%
♦ 12µA Quiescent Current
♦ 3µA Shutdown Current
♦ 100% Maximum Duty Cycle for Low Dropout
♦ Current-Limiting and Overtemperature Protection
♦ Small 6-Pin SOT23 Package
MAX1836/MAX1837
24V Internal Switch, 100% Duty Cycle,
Step-Down Converters
________________________________________________________________ Maxim Integrated Products 1
19-1919; Rev 1; 01/02
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.
PART
PRESET OUTPUT
VOLTAGE (V)
LOAD
CURRENT (mA)
MAX1836EUT50 5 125
MAX1836EUT33 3.3 125
MAX1837EUT50 5 250
MAX1837EUT33 3.3 250
Selector Guide
MAX1836
MAX1837
IN
GND
LX
SHDN
FB
OUT
NOTE: HIGH-CURRENT PATHS SHOWN WITH BOLD LINES.
OUTPUT
3.3V OR 5V
INPUT
4.5V TO 24V
Typical Operating Circuit
GND
LX IN
1 6 OUT
5 SHDN
FB
MAX1836
MAX1837
SOT23
TOP VIEW
2
3 4
Pin Configuration
Note: The MAX1836/MAX1837 require special solder tempera-
ture profile described in the Absolute Maximum Ratings.
PART TEMP RANGE
PIN-
PA C K A G E TOP
M ARK
MAX1836EUT50-T -40°C to +85°C 6 SOT23-6 AANW
MAX1836EUT33-T -40°C to +85°C 6 SOT23-6 AANY
MAX1837EUT50-T -40°C to +85°C 6 SOT23-6 AANX
MAX1837EUT33-T -40°C to +85°C 6 SOT23-6 AANZ
Ordering Information