MAXIM MAX1836, MAX1837 Technical data

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 VIN. 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, low­power, 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

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

LXIN

16OUT

5 SHDN

FB

MAX1836
MAX1837

SOT23

TOP VIEW

2

34

Pin Configuration

Note: The MAX1836/MAX1837 require special solder tempera­ture profile described in the Absolute Maximum Ratings.

PART

TEMP RANGE

PIN-

TOP

M ARK

MAX1836EUT50-T

AANW

MAX1836EUT33-T

AANY

MAX1837EUT50-T

AANX

MAX1837EUT33-T

AANZ

Ordering Information

查询MAX1836供应商

PA C K A G E

-40°C to +85°C

-40°C to +85°C

-40°C to +85°C

-40°C to +85°C

6 SOT23-6

6 SOT23-6

6 SOT23-6

6 SOT23-6

MAX1836/MAX1837

24V Internal Switch, 100% Duty Cycle,
Step-Down Converters

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

IN, SHDN to GND ...................................................-0.3V to +25V

LX to GND.......................................................-2V to (V

IN

+ 0.3V)

OUT, FB to GND.......................................................-0.3V to +6V

Continuous Power Dissipation (T

A

= +70°C) (Note 1)

6-Pin SOT23 (derate 8.7mW/°C above +70°C)............696mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Note 1: Thermal properties are specified with product mounted on PC board with 1in

2

of copper area and still air.

)

ELECTRICAL CHARACTERISTICS

(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.)

Dual Mode is a trademark of Maxim Integrated Products, Inc.

Input Supply Range V

Input Undervoltage Lockout
Threshold

Input Supply Current I

Input Supply Current in Dropout I
Input Shutdown Current SHDN = GND 3 7 µA

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IN

V

UVLO

IN

IN (D ROP) VIN

VIN rising 3.55 4.0 4.4

VIN falling 3.45 3.9 4.3

= 5V 18 µA

4.5 24 V

12 25 µA

V

FB = GND,
I

= 0 to 125mA

Output Voltage (Preset Mode) V

Output Voltage Range
(Adjustable Mode)

Feedback Set Voltage
(Adjustable Mode)

OUT Bias Current V

FB Bias Current I

FB Dual ModeTM Threshold VFB rising or falling 50 100 150 mV

LX Switch Minimum Off-Time t

LX Switch Maximum On-Time t

LX Switch On-Resistance R

LX Current Limit I

LX Zero-Crossing Threshold -75 +75 mV

OUT

V

OUT

V

FB

FB

OFF( M IN)

ON (M AX

LX

LIM

LOAD

(MAX1836) or
250mA (MAX1837)

(Note 2) 1.25 V

= 5V 2.5 7.4 µA

OUT

VFB = 0 or 1.25V, TA = +25°C -25 +25 nA

VFB = 1.3V 7 10 13 µs

VIN = 6V 1.1 2 Ω

MAX1836 250 312 450

MAX1837 500 625 850

MAX183_EUT50 4.80 5.00 5.20

MAX183_EUT33 3.168 3.30 3.432

IN

1.200 1.25 1.300 V

0.2 0.4 0.6 µs

V

V

mA

MAX1836/MAX1837

24V Internal Switch, 100% Duty Cycle,

Step-Down Converters

_______________________________________________________________________________________ 3

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.)

)

ELECTRICAL CHARACTERISTICS

(Circuits of Figures 1 (MAX1836) and 2 (MAX1837), VIN= 12V, SHDN = IN, TA= -40°C to +85°C, unless otherwise noted.) (Note 4)

Zero-Crossing Timeout LX does not rise above the threshold 30 µs

LX Switch Leakage Current VIN = 18V, LX = GND, TA = +25°C1µA

Dropout Voltage V

Line Regulation VIN = 5V to 24V 0.05 %

Load Regulation

Shutdown Input Threshold V

Shutdown Leakage Current I
Thermal Shutdown 10°C hysteresis (typ) 160 °C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DROPOUTIOUT

SHDN

SHDN

= 100mA, VIN = 5V 120 mV

I

= 0 to 125mA (MAX1836) or 250mA

OUT

(MAX1837)

VIN = 4.5V to 24V (Note 3) 0.8 2.4 V

V

= 0 or 24V -1 +1 µA

SHDN

0.3 %

Input Supply Range V

Input Undervoltage Lockout
Threshold

Input Supply Current I
Input Shutdown Current SHDN = GND 7 µA

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

4.5 24 V

V

25 µA

V

IN

UVLO

IN

VIN rising 3.55 4.4

VIN falling 3.45 4.3

FB = GND,
I

= 0 to 125mA

Output Voltage (Preset Mode) V

Output Voltage Range
(Adjustable Mode)

Feedback Set Voltage
(Adjustable Mode)

OUT Bias Current V

FB Dual Mode Threshold VFB rising or falling 50 150 mV

LX Switch Minimum Off-Time t

LX Switch Maximum On-Time t

LX Switch On-Resistance R

LX Current Limit I

OUT

V

OUT

V

FB

OFF( M IN)

ON (M AX

LX

LIM

LOAD

(MAX1836) or
250mA (MAX1837)

(Note 2) 1.25 V

= 5V 7.4 µA

OUT

VFB = 1.3V 7 13 µs

VIN = 6V 2 Ω

MAX1836 250 450

MAX1837 500 900

MAX183_EUT50 4.80 5.20

MAX183_EUT33 3.168 3.432

IN

1.200 1.300 V

0.2 0.6 µs

V

V

mA

MAX1836/MAX1837

24V Internal Switch, 100% Duty Cycle,
Step-Down Converters

4 _______________________________________________________________________________________

Typical Operating Characteristics

(Circuits of Figures 1 (MAX1836) and 2 (MAX1837), VIN= 12V, SHDN = IN, TA = +25°C.)

3.27

3.29

3.28

3.31

3.30

3.32

3.33

0 10050 150 200

MAX1836EUT33

OUTPUT VOLTAGE vs. LOAD CURRENT

MAX1836/7 toc01

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

VIN = 5V

VIN = 9V to 12V

FIGURE 1

100

95

90

85

80

70

0.1 10 1001 1000

MAX1836EUT33

EFFICIENCY vs. LOAD CURRENT

MAX1836/7 toc02

LOAD CURRENT (mA)

EFFICIENCY (%)

75

VIN = 9V

VIN = 12V

VIN = 5V

FIGURE 1
V

OUT

= 3.3V

3.27

3.29

3.28

3.31

3.30

3.32

3.33

0 150 20050 100 250 300 350

MAX1837EUT33

OUTPUT VOLTAGE vs. LOAD CURRENT

MAX1836/7 toc03

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

VIN = 9V

VIN = 5V

VIN = 12V

FIGURE 2

100

95

90

85

80

70

0.1 10 1001 1000

MAX1837EUT33

EFFICIENCY vs. LOAD CURRENT

MAX1836/7 toc04

LOAD CURRENT (mA)

EFFICIENCY (%)

75

VIN = 9V

VIN = 12V

VIN = 5V

FIGURE 2
V

OUT

= 3.3V

0

40

20

100

80

60

160

140

120

180

0 100 15050 200 250 300 350

MAX1837EUT33

SWITCHING FREQUENCY vs. LOAD CURRENT

MAX1836/7 toc05

LOAD CURRENT (mA)

FREQUENCY (kHz)

VIN = 9V

VIN = 5V

VIN = 12V

FIGURE 2
V

OUT

= 3.3V

3.27

3.29

3.28

3.31

3.30

3.32

3.33

0 4 8 12162024

MAX1837EUT33

OUTPUT VOLTAGE vs. INPUT VOLTAGE

MAX1836/7 toc06

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

I

OUT

= 10mA

I

OUT

= 200mA

FIGURE 2
V

OUT

= 3.3V

L1 = 47µH

Note 2: When using the shutdown input, the maximum output voltage allowed with external feedback is 5.5V. If the output voltage is

set above 5.5V, connect shutdown to the input.

Note 3: Shutdown input minimum slew rate (rising or falling) is 10V/ms.
Note 4: Specifications to -40°C are guaranteed by design, not production tested.

PARAMETER

CONDITIONS

UNITS

LX Zero-Crossing Threshold -75

mV

Shutdown Input Threshold

VIN = 4.5V to 24V (Note 3) 0.8 2.4 V

Shutdown Leakage Current I

SHDN

V

SHDN

= 0 or 24V -1 +1 µA

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)

SYMBOL

V

SHDN

MIN TYP MAX

+75

MAX1836/MAX1837

24V Internal Switch, 100% Duty Cycle,

Step-Down Converters

_______________________________________________________________________________________ 5

Typical Operating Characteristics (continued)

(Circuits of Figures 1 (MAX1836) and 2 (MAX1837), VIN= 12V, SHDN = IN, TA = +25°C.)

MAX1837EUT33

EFFICIENCY vs. INPUT VOLTAGE

100

V

I

OUT

OUT

L1 = 47µH

= 200mA

95

90

85

EFFICIENCY (%)

80

I

= 10mA

75

70

0 4 8 12162024

OUT

INPUT VOLTAGE (V)

OUTPUT VOLTAGE vs. LOAD CURRENT

5.04

VIN = 12V TO 24V

5.02

FIGURE 2

= 3.3V

MAX1836/7 toc07

MAX1837EUT50

VIN = 9V

SWITCHING FREQUENCY vs. INPUT VOLTAGE

100

10

FREQUENCY (kHz)

1

0812

MAX1837EUT33

4

INPUT VOLTAGE (V)

MAX1836/7 toc10

I

= 200mA

OUT

FIGURE 2

= 3.3V

V

OUT

L1 = 47µH

I

= 10mA

OUT

16 2420

MAX1837EUT50

EFFICIENCY vs. LOAD CURRENT

100

FIGURE 6

= 5V

V

OUT

95

VIN = 12V

90

PEAK INDUCTOR CURRENT vs. INPUT VOLTAGE

MAX1837EUT33

1000

FIGURE 2

= 3.3V

V

OUT

MAX1836/7 toc08

L1 = 47µH

800

600

400

PEAK INDUCTOR CURRENT (mA)

200

LIMITED BY

t

ON(MIN)

0

0 4 8 12162024

VIN = 9V

VIN = 7V

INPUT VOLTAGE (V)

LIMITED BY

MAX1836/7 toc11

I

OUT

I

= 200mA

I

LIM

OUT

MAX1836/7 toc09

= 10mA

5.00

OUTPUT VOLTAGE (V)

4.98

FIGURE 6

4.96
0 10050 150 200 250 300

VIN = 7V

LOAD CURRENT (mA)

MAX1837EUT50

DROPOUT VOLTAGE vs. LOAD CURRENT

400

FIGURE 6

= 5V

V

350

OUT

300

250

200

150

DROPOUT VOLTAGE (mV)

100

50

0

0 100 200 300

LOAD CURRENT (mA)

MAX1836/7 toc12

85

EFFICIENCY (%)

80

75

70

0.1 10 1001 1000

VIN = 18V

LOAD CURRENT (mA)

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE

15

14

13

12

SUPPLY CURRENT (µA)

11

10

0 4 8 12 16 20 24

INPUT VOLTAGE (V)

VIN = 24V

MAX1836/7 toc13