Datasheet

ManualsBrandsMaxim Integrated ManualsActive ComponentsPMIC - voltage regulators - DC DC switch controllers Tape on Full reel

General Description

The MAX1836/MAX1837 high-efficiency step-down con-

verters provide a preset 3.3V or 5V output voltage from

supply voltages as high as 24V. Using external feedback

resistors, the output voltage can be adjusted from 1.25V

to V

. 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 volt-

age (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 inter-

nal switching MOSFETs are available in 6-pin SOT23

and 3mm x 3mm TDFN packages, making them ideal

for low-cost, low-power, space-sensitive applications.

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 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

● Handheld Devices

Features

● 4.5V to 24V Input Voltage Range

● Preset 3.3V or 5V Output

● Adjustable Output from 1.25V to V

● Output Currents Up to 125mA (MAX1836) or

250mA (MAX1837)

● Efficiency Over 90%

● 12μA Quiescent Current

● 3μA Shutdown Current

● 100% Maximum Duty Cycle for Low Dropout

● Small 6-Pin SOT23 and TDFN Packages

Selector Guide appears at end of data sheet.

19-1919; Rev 3; 7/06

*EP = Exposed pad.

T = Tape and reel.

PART TEMP RANGE

PIN-

PACKAGE

TOP

MARK

MAX1836ETT33-T -40°C to +85°C 6 TDFN-EP* AJG

MAX1836ETT50-T -40°C to +85°C 6 TDFN-EP* AJE

MAX1836EUT33-T -40°C to +85°C 6 SOT23 AANY

MAX1836EUT50-T -40°C to +85°C 6 SOT23 AANW

MAX1837ETT33-T -40°C to +85°C 6 TDFN-EP* AJH

MAX1837ETT50-T -40°C to +85°C 6 TDFN-EP* AJF

MAX1837EUT33-T -40°C to +85°C 6 SOT23 AANZ

MAX1837EUT50-T -40°C to +85°C 6 SOT23 AANX

MAX1836

MAX1837

GND

SHDN

OUT

NOTE: HIGH-CURRENT PATHS SHOWN WITH BOLD LINES.

OUTPUT

3.3V OR 5V

INPUT

4.5V TO 24V

GND

LXIN

1 6 OUT

5 SHDN

MAX1836

MAX1837

MAX1836

MAX1837

SOT23

TDFN

TOP VIEW

GND

1FB

6 OUT

5 SHDN

MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle,

Step-Down Converters

Typical Operating Circuit Pin Congurations

Ordering Information

EVALUATION KIT AVAILABLE

Summary of content (15 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters 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 can be adjusted from 1.25V to VIN. An internal current-limited switching MOSFET delivers load currents up to 125mA (MAX1836) or 250mA (MAX1837).
PAGE 2
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Absolute Maximum Ratings IN, SHDN to GND...................................................-0.3V to +25V LX to GND.......................................................-2V to (VIN + 0.3V) OUT, FB to GND.......................................................-0.3V to +6V Continuous Power Dissipation (TA = +70°C) (Note 1) 6-Pin SOT23 (derate 8.7mW/°C above +70°C)...........696mW 6-Pin TDFN (derate 24.4mW/°C above +70°C).........
PAGE 3
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Electrical Characteristics (continued) (Circuits of Figures 1 (MAX1836) and 2 (MAX1837), VIN = 12V, SHDN = IN, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.
PAGE 4
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Electrical Characteristics (continued) (Circuits of Figures 1 (MAX1836) and 2 (MAX1837), VIN = 12V, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 4) PARAMETER SYMBOL CONDITIONS MIN LX Zero-Crossing Threshold TYP MAX UNITS -75 +75 mV Shutdown Input Threshold VSHDN VIN = 4.5V to 24V (Note 3) 0.8 2.
PAGE 5
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Typical Operating Characteristics (continued) (Circuits of Figures 1 (MAX1836) and 2 (MAX1837), VIN = 12V, SHDN = IN, TA = +25°C.) 85 IOUT = 200mA 80 10 IOUT = 10mA 75 70 0 4 8 IOUT = 10mA 12 16 20 1 24 0 8 12 16 20 5.00 VIN = 7V 4.98 400 200 LIMITED BY tON(MIN) 0 0 95 FIGURE 6 0 50 100 150 200 250 VIN = 9V VIN = 12V 90 250 200 150 100 20 24 VIN = 7V VIN = 18V 0.
PAGE 6
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Typical Operating Characteristics (continued) (Circuits of Figures 1 (MAX1836) and 2 (MAX1837), VIN = 12V, SHDN = IN, TA = +25°C.) MAX1837EUT50 LOAD TRANSIENT 400mA MAX1837EUT50 LINE TRANSIENT MAX1836/7 toc14 200mA 20V A 0 5.02V 5.1V B 4.
PAGE 7
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Pin Description PIN NAME FUNCTION 1 FB Dual-Mode Feedback Input. Connect to GND for the preset 3.3V (MAX183_EUT33) or 5.0V (MAX183_ EUT50) output. Connect to a resistive divider between the output and FB to adjust the output voltage between 1.25V and VIN, and connect the OUT pin to GND. When setting output voltages above 5.5V, permanently connect SHDN to IN. 2 GND 3 IN Input Voltage. 4.5V to 24V input range.
PAGE 8
MAX1836/MAX1837 INPUT 4.5V OR 24V CIN 24V Internal Switch, 100% Duty Cycle, Step-Down Converters L1 LX IN SHDN OUTPUT 3.3V OR 5V D1 COUT VSENSE OUT R Q FB MAXIMUM OFF-TIME DELAY S Q TRIG 100mV Q MAX1836 MAX1837 TRIG MAXIMUM ON-TIME DELAY VSET 1.25V GND Figure 3. Functional Diagram When the output voltage is too low, an error comparator sets a flip-flop, which turns on the internal p-channel MOSFET and begins a switching cycle (Figure 3).
PAGE 9
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Input-Output (Dropout) Voltage the Selector Guide. For example, the MAX1836EUT33 has a preset 3.3V output voltage. A step-down converter’s minimum input-to-output voltage differential (dropout voltage) determines the lowest useable input supply voltage. In battery-powered systems, this limits the useful end-of-life battery voltage.
PAGE 10
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters The inductor’s saturation current rating must be greater than the peak switching current, which is determined by the switch current limit plus the overshoot due to the 300ns current-sense comparator propagation delay: capacitor selection, but final values should be set by testing a prototype or evaluation circuit. As a general rule, a smaller amount of charge delivered in each pulse results in less output ripple.
PAGE 11
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Table 1. Component Suppliers SUPPLIER PHONE FAX WEBSITE Coilcraft 847-639-6400 847-639-1469 www.coilcraft.com Coiltronics 561-241-7876 561-241-9339 www.coiltronics.com Sumida USA 847-956-0666 847-956-0702 www.sumida.com Toko 847-297-0070 847-699-1194 www.tokoam.com AVX 803-946-0690 803-626-3123 www.avxcorp.com Kemet 408-986-0424 408-986-1442 www.kemet.com Panasonic 847-468-5624 847-468-5815 www.
PAGE 12
MAX1836/MAX1837 INPUT 4.5V TO 24V CIN 10µF 25V IN SHDN 24V Internal Switch, 100% Duty Cycle, Step-Down Converters L1 47µH LX OUTPUT 5V COUT 68µF 10V D1 MAX1837 OUT INPUT 3.6V TO 18V CIN 10µF IN L1 47µH LX OUT SHDN OUTPUT -3.3V OR -5V GND FB GND COUT 100µF D1 MAX1836 MAX1837 FB NOTE: HIGH-CURRENT PATHS SHOWN WITH BOLD LINES. CIN = TAIYO YUDEN TMK432BJ106KM L1 = SUMIDA CDRH5D28-470 COUT = SANYO POSCAP 10TPC68M D1 = NIHON EP05Q03L Figure 7.
PAGE 13
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. www.maximintegrated.
PAGE 14
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. www.maximintegrated.
PAGE 15
MAX1836/MAX1837 24V Internal Switch, 100% Duty Cycle, Step-Down Converters Package Information (continued) For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.