________________________________________________________________

Maxim Integrated Products

_______________General Description

The MAX639/MAX640/MAX653 step-down switching

regulators provide high efficiency over a wide range of

load currents, delivering up to 225mA. A current-limiting

pulse-frequency-modulated (PFM) control scheme gives

the devices the benefits of pulse-width-modulated

(PWM) converters (high efficiency at heavy loads), while

using only 10µA of supply current (vs. 2mA to 10mA for

PWM converters). The result is high efficiency over a

wide range of loads.

The MAX639/MAX640/MAX653 input range is 4V to

11.5V, and the devices provide lower preset output volt-

ages of 5V, 3.3V, and 3V, respectively. Or, the output

can be user-adjusted to any voltage from 1.3V to the

input voltage.

The MAX639/MAX640/MAX653 have an internal 1A power

MOSFET switch, making them ideal for minimum-compo-

nent, low- and medium-power applications. For increased

output drive capability, use the MAX649/MAX651/MAX652

step-down controllers, which drive an external P-channel

FET to deliver up to 5W.

________________________Applications

9V Battery to 5V, 3.3V, or 3V Conversion

High-Efficiency Linear Regulator Replacement

Portable Instruments and Handy-Terminals

5V-to-3.3V Converters

____________________________Features

♦ High Efficiency for a Wide Range of Load Currents

♦ 10µA Quiescent Current

♦ Output Currents Up to 225mA

♦ Preset or Adjustable Output Voltage:

5.0V (MAX639)

3.3V (MAX640)

3.0V (MAX653)

♦ Low-Battery Detection Comparator

♦ Current-Limiting PFM Control Scheme

______________Ordering Information

Ordering Information continued on last page.

* Contact factory for dice specifications.

MAX639/MAX640/MAX653

5V/3.3V/3V/Adjustable, High-Efficiency,

Low I

, Step-Down DC-DC Converters

19-4505; Rev 3; 8/97

PART TEMP. RANGE PIN-PACKAGE

MAX639CPA

0°C to +70°C 8 Plastic DIP

MAX639CSA 0°C to +70°C 8 SO

MAX639C/D 0°C to +70°C Dice*

MAX639

MAX640

MAX653

DIP/SO

TOP VIEW

VFB

SHDN

V+

VOUT

LBO

LBI

GND

__________________Pin Configuration

GND

MAX639

SHDN

VOUT

LBO

LOW-BATTERY

DETECTOR

OUTPUT

ON/OFF

LBI

LOW-BATTERY

DETECTOR

INPUT

OUTPUT

225mA

INPUT

5.5V TO 11.5V

V+

VFB

__________Typical Operating Circuit

MAX639ESA -40°C to +85°C 8 SO

MAX639EPA -40°C to +85°C 8 Plastic DIP

MAX639MJA -55°C to +125°C 8 CERDIP

EVALUATION KIT

INFORMATION INCLUDED

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 408-737-7600 ext. 3468.

MAX639/MAX640/MAX653

5V/3.3V/3V/Adjustable, High-Efficiency,

Low I

, Step-Down DC-DC Converters

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V+ = 9V for the MAX639, V+ = 5V for the MAX640/MAX653, I

LOAD

= 0mA, T

= T

MIN

to T

MAX

, typical values are at T

= +25°C,

unless otherwise noted.)

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.

PARAMETER MIN TYP MAX UNITS

Dropout Voltage 0.5 V

Output Voltage (Note 2)

2.88 3.00 3.12

V3.17 3.30 3.43

Supply Current

Supply Voltage 4.0 11.5 V

10 20 µA

4.80 5.00 5.20

Efficiency

CONDITIONS

MAX653

OUT

= 100mA, L = 100µH

MAX653, V+ = 4.0V to 11.5V, 0mA < I

OUT

< 100mA

MAX640, V+ = 4.0V to 11.5V, 0mA < I

OUT

< 100mA

MAX639

MAX640

SHDN = V+, no load

MAX639, V+ = 6.0V to 11.5V, 0mA < I

OUT

< 100mA

V+...........................................................................................12V

LX .........................................................(V+ - 12V) to (V+ + 0.3V)

LBI, LBO, VFB, SHDN

, VOUT........................-0.3V to (V+ + 0.3V)

LX Output Current (Note 1)......................................................1A

LBO Output Current............................................................10mA

Continuous Power Dissipation (T

= +70°C)

Plastic DIP (derate 9.09mW/°C above +70°C) .............727mW

SO (derate 5.88mW/°C above +70°C)..........................471mW

CERDIP (derate 8.00mW/°C above +70°C)..................640mW

Operating Temperature Ranges:

MAX639C_ _ .......................................................0°C to +70°C

MAX639E_ _ ....................................................-40°C to +85°C

MAX639MJA..................................................-55°C to +125°C

Storage Temperature Range.............................-65°C to +160°C

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

OUT

= 100mA, L = 100µH

OUT

= 25mA, L = 470µH

OUT

= 100mA, L = 100µH

OUT

= 25mA, L = 470µH

OUT

= 100mA, L = 100µH

OUT

= 25mA, L = 470µH

Switch On-Time

V+ = 9V, V

OUT

= 5V

V+ = 6V, V

OUT

= 3V

42.5 50.0 57.5

V+ = 9V, V

OUT

= 3.3V

V+ = 4V, V

OUT

= 3.3V

µs

10.6 12.5 14.4

V+ = 9V, V

OUT

= 3V

V+ = 4V, V

OUT

= 3V

14.2 16.7 19.2

7.5 8.8 10.1

60.7 71.4 82.1

7.1 8.3 9.5

MAX653

MAX639

MAX640

Switch Off-Time

V+ = 9V, V

OUT

= 5V

V+ = 6V, V

OUT

= 3V

14.6 17.2 19.8

V+ = 9V, V

OUT

= 3.3V

V+ = 4V, V

OUT

= 3.3V

µs

9.0 11.7 13.5

V+ = 9V, V

OUT

= 3V

V+ = 4V, V

OUT

= 3V

16.6 19.5 22.4

13.3 15.6 17.9

14.6 17.2 19.8

MAX653

MAX639

MAX640

Note 1: Peak inductor current must be limited to 600mA by using an inductor of 100µH or greater.

MAX639/MAX640/MAX653

5V/3.3V/3V/Adjustable, High-Efficiency,

Low I

, Step-Down DC-DC Converters

_______________________________________________________________________________________ 3

__________________________________________Typical Operating Characteristics

(Circuit of Figure 3, internal feedback, L = 100µH, T

= +25°C, unless otherwise noted.)

100

10µ 100µ 1

EFFICIENCY vs.

OUTPUT CURRENT

MAX639-1

OUTPUT CURRENT (A)

EFFICIENCY (%)

1m 10m 100m

L = 100µH

+ = 9V

MAX639

MAX640

MAX653

100

10µ 100µ

EFFICIENCY vs.

OUTPUT CURRENT

MAX639-2

OUTPUT CURRENT (A)

EFFICIENCY (%)

1m 10m

MAX639, V+ = 6V

MAX640, V+ = 4.3V

MAX653, V+ = 4V

100m

L = 470µH

100

10µ 100µ

EFFICIENCY vs.

OUTPUT CURRENT

MAX639-3

OUTPUT CURRENT (A)

EFFICIENCY (%)

1m 10m

MAX639

MAX640

MAX653

100m

L = 470µH

V+ = 9V

Note 2: Output guaranteed by correlation to measurements of device parameters (i.e., switch on-resistance, on-times, off-times, and

output voltage trip points).

ELECTRICAL CHARACTERISTICS (continued)

(V+ = 9V for the MAX639, V+ = 5V for the MAX640/MAX653, I

LOAD

= 0mA, T

= T

MIN

to T

MAX

, typical values are at T

= +25°C,

unless otherwise noted.)

PARAMETER

0.4 1.2

MIN TYP MAX

mAV

LBO

= 0.4V

UNITS

LBO Leakage Current 0.001 0.1 µAV

LBO

= 11.5V

LBO Delay 25 µs50mV overdrive

2.5

SHDN Threshold

0.80 1.15 2.00 V

SHDN Pull-Up Current

0.10 0.20 0.40

Ω

µA

SHDN = 0V

µA

= +25°C

= T

MIN

to T

MAX

MAX639

MAX640/MAX653

2.8

LX Switch Leakage

0.003 1.0

30.0

VFB Bias Current 4.0 15.0 nA

VFB Dual-Mode Trip Point

LX Switch On-Resistance

0.8 1.5

VFB Threshold

1.26 1.28 1.30

1.24 1.28 1.32

LBI Bias Current 2 10

LBI Threshold

1.26 1.28 1.30

1.24 1.28 1.32

LBO Sink Current

0.8 2.5

CONDITIONS

V+ = 6V, T

= T

MIN

to T

MAX

, MAX639

V+ = 4V, T

= T

MIN

to T

MAX

, MAX640/MAX653

V+ = 11.5V, V

= 0V

VFB = 2V

V+ = 9V, T

= +25°C, MAX639/MAX640/MAX653

MAX6_ _C

MAX6_ _E/M

LBI

= 2V

MAX6_ _C

MAX6_ _E/M

Part #	MAX653ESA
Description	3V ADJUSTABLE, HIGH EFFICIENCY, STEP-DOWN DC- - Bulk
Category	IC
Availability	In Stock
Qty	5

Qty	Price
1 - 1	$12.12299
2 - 2	$9.64328
3 - 3	$9.09224
4 +	$8.44935

MAX653ESA

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