Rainbow Electronics MAX8640Z User Manual

General Description

The MAX8640Y/MAX8640Z step-down converters are
optimized for applications where small size, high effi­ciency, and low output ripple are priorities. They utilize
a proprietary PWM control scheme that optimizes the
switching frequency for high efficiency with small exter­nal components and maintains low output ripple volt­age at all loads. The MAX8640Z switches at up to
4MHz to allow a tiny 1µH inductor and 2.2µF output
capacitor. The MAX8640Y switches at up to 2MHz for
higher efficiency while still allowing small 2.2µH and

4.7µF components. Output current is guaranteed up to
500mA, while typical quiescent current is 24µA.
Factory-preset output voltages from 0.8V to 2.5V elimi­nate external feedback components.

Internal synchronous rectification greatly improves effi­ciency and replaces the external Schottky diode
required in conventional step-down converters. Internal
fast soft-start eliminates inrush current so as to reduce
input capacitor requirements.

The MAX8640Y/MAX8640Z are available in the tiny 6­pin, SC70 lead-free package (2.0mm x 2.1mm footprint,

1.1mm max height).

Applications

Microprocessor/DSP Core Power

I/O Power

Cell Phones, PDAs, DSCs, MP3s

Other Handhelds Where Space Is Limited

Features

♦ Tiny 6-Pin SC70 Package
♦ 500mA Guaranteed Output Current
♦ 4MHz or 2MHz PWM Switching Frequency
♦ Tiny External Components: 1µH/2.2µF or

2.2µH/4.7µF

♦ 24µA Quiescent Current
♦ Factory Preset Outputs from 0.8V to 2.5V
♦ ±1% Initial Accuracy
♦ Low Output Ripple at All Loads
♦ Ultrasonic Skip Mode Down to 1mA Loads
♦ Ultra-Fast Line- and Load-Transient Response
♦ Fast Soft-Start Eliminates Inrush Current

MAX8640Y/MAX8640Z

500mA, 4MHz/2MHz Synchronous

Step-Down DC-DC Converters in SC70

________________________________________________________________ Maxim Integrated Products 1

19-3997; Rev 0; 5/06

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.

EVALUATION KIT

AVAILABLE

Ordering Information

Pin Configuration

L1

1μH OR 2.2μH

C2

2.2μF OR

4.7μF

C1

2.2μF

OUT

LX

GND

IN

SHDN

ON/OFF

MAX8640Y
MAX8640Z

INPUT

2.7V TO 4.9V

OUTPUT

0.8V TO 2.5V

UP TO 500mA

Typical Operating Circuit

Ordering Information continued and Selector Guide appears
at end of data sheet.

*Contact factory for availability of each version.
+Denotes lead-free package.

Note: All devices are specified over the -40°C to +85°C
operating temperature range.

PART*

MAX8640YEXT08+T 6 SC70-6 X6S-1

MAX8640YEXT11+T 6 SC70-6 X6S-1

MAX8640YEXT12+T 6 SC70-6 X6S-1

MAX8640YEXT13+T 6 SC70-6 X6S-1

MAX8640YEXT15+T 6 SC70-6 X6S-1

MAX8640YEXT16+T 6 SC70-6 X6S-1

MAX8640YEXT18+T 6 SC70-6 X6S-1

MAX8640YEXT19+T 6 SC70-6 X6S-1

MAX8640YEXT25+T 6 SC70-6 X6S-1

PIN­PACKAGE

PKG

CODE

TOP

MARK

ACQ

ACR

ACS

ACG

ADD

ADB

ACH

ACJ

ACI

TOP VIEW

GND

OUT

+

1

LX

MAX8640Y

2

MAX8640Z

34

SC70

6IN

5 GND

SHDN

MAX8640Y/MAX8640Z

500mA, 4MHz/2MHz Synchronous
Step-Down DC-DC Converters in SC70

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 to GND .................................................................-0.3V to +6V

LX, OUT, SHDN to GND ..............................-0.3V to (V

IN

+ 0.3V)

LX Current (Note 1) ........................................................0.8A

RMS

OUTPUT Short Circuit to GND ...................................Continuous

Continuous Power Dissipation (T

A

= +70°C)

6-Pin SC70 (derate 3.1mW/°C above +70°C)..............245mW

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

ELECTRICAL CHARACTERISTICS

(VIN= 3.6V, SHDN = IN, TA= -40°C to +85°C, typical values are at TA= +25°C, unless otherwise noted.) (Note 2)

)

)

Note 1: LX has internal clamp diodes to IN and GND. Applications that forward bias these diodes should not exceed the IC’s package

power-dissipation limit.

Note 2: All devices are 100% production tested at T

A

= +25°C. Limits over the operating temperature range are guaranteed by design.

Supply Range V

UVLO Threshold UVLO VIN rising, 100mV hysteresis 2.44 2.6 2.70 V

Supply Current I

Output Voltage Range V

Output Voltage Accuracy
(Falling Edge)

Output Load Regulation
(Voltage Positioning)

SHDN Logic Input Level

SHDN Logic Input Bias Current I

Peak Current Limit I

Valley Current Limit I

Rectifier Off-Current Threshold I

On-Resistance

LX Leakage Current I

Minimum On and Off Times

Thermal Shutdown +160 °C

Thermal-Shutdown Hysteresis 20 °C

PARAMETER

SYMBOL CONDITIONS MIN TYP MAX UNITS

IN

No load, no switching 24 48

CC

SHDN = GND

OUT

V

V

IH,IL

LIMP

LIMN

LXOFF

R

ONP

R

ONN

LXLKG

t

ON(MIN

t

OFF(MIN

Factory preset 0.8 2.5 V

I

= 0mA, TA = +25°C -1 0 +1

LOAD

I

= 0mA, TA = -40°C to +85°C -2 +2

LOAD

Equal to inductor DC resistance R

VIN = 2.7V to 4.9V 1.4

IH

VIN = 2.7V to 4.9V 0.4

IL

VIN = 4.9V,
SHDN = GND or IN

pFET switch 590 770 1400 mA

nFET rectifier 450 650 1300 mA

nFET rectifier 10 40 70 mA

pFET switch, ILX = -40mA 0.6 1.2

nFET rectifier, ILX = 40mA 0.35 0.7

V

= 4.9V, LX = GND

IN

to IN, SHDN = GND

2.7 4.9 V

TA = +25°C 0.01 0.1

T

= +85°C 0.1

A

L

TA = +25°C 0.001 1

= +85°C 0.01

T

A

TA = +25°C 0.1 1

T

= +85°C 1

A

95

95

µA

%

V/A

V

µA

Ω

µA

ns

MAX8640Y/MAX8640Z

500mA, 4MHz/2MHz Synchronous

Step-Down DC-DC Converters in SC70

_______________________________________________________________________________________ 3

Typical Operating Characteristics

(VIN= 3.6V, V

OUT

= 1.5V, MAX8640Z, L = Murata LQH32CN series, TA= +25°C, unless otherwise noted.)

EFFICIENCY vs. LOAD CURRENT

1.8V OUTPUT

LOAD CURRENT (mA)

EFFICIENCY (%)

MAX8640Y/Z toc01

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100 1000

MAX8640YEXT18

NO-LOAD SUPPLY CURRENT

vs. SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (μA)

MAX8640Y/Z toc02

2.9 3.3 3.7 4.1 4.5 4.9

5

10

15

20

25

30

35

MAX8640ZEXT15

MAX8640YEXT18

SWITCHING FREQUENCY

vs. LOAD CURRENT

LOAD CURRENT (mA)

SWITCHING FREQUENCY (MHz)

MAX8640Y/Z toc03

0 100 200 300 400 500

0.1

1

10

MAX8640ZEXT15

MAX8640YEXT18

OUTPUT VOLTAGE vs. LOAD CURRENT

(VOLTAGE POSITIONING)

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

MAX8640Y/Z toc04

0 100 200 300 400 500

1.30

1.35

1.40

1.45

1.50

1.55

MAX8640ZEXT15

I

LX

V

LX

V

OUT

200mA/div

2V/div

20mV/div
(AC-COUPLED)

10μs/div

LIGHT-LOAD SWITCHING WAVEFORMS

(I

OUT

= 1mA)

MAX8640Y/Z toc05

I

LX

V

LX

V

OUT

200mA/div

2V/div
0V

0mA

20mV/div
(AC-COUPLED)

200ns/div

MEDIUM-LOAD SWITCHING WAVEFORMS

(I

OUT

= 40mA)

MAX8640Y/Z toc06

I

LX

V

LX

V

OUT

200mA/div

2V/div

0V

0mA

20mV/div
(AC-COUPLED)

200ns/div

HEAVY-LOAD SWITCHING WAVEFORMS

(I

OUT

= 300mA)

MAX8640Y/Z toc07