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HOJAS TÉCNICAS DE COMPONENTES UTILIZADOS

This datasheet has been download from: www.datasheetcatalog.com

Datasheets for electronics components.

19-0113; Rev. 2; 1/95

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

3.3V/5V/Adjustable-Output,

Step-Up DC-DC Converters

_______________General Description

The MAX756/MAX757 are CMOS step-up DC-DC switching regulators for small, low input voltage or battery-powered systems. The MAX756 accepts a positive input voltage down to 0.7V and converts it to a higher pinselectable output voltage of 3.3V or 5V. The MAX757 is an adjustable version that accepts an input voltage down to 0.7V and generates a higher adjustable output voltage in the range from 2.7V to 5.5V. Typical full-load efficiencies for the MAX756/MAX757 are greater than 87%.

The MAX756/MAX757 provide three improvements over previous devices. Physical size is reduced—the high switching frequencies (up to 0.5MHz) made possible by

MOSFET power transistors allow for tiny (<5mm diameter) surface-mount magnetics. Efficiency is improved to 87%

(10% better than with low-voltage regulators fabricated in bipolar technology). Supply current is reduced to 60µA by CMOS construction and a unique constant-off-time pulse-frequency modulation control scheme.

________________________Applications

3.3V to 5V Step-Up Conversion

Palmtop Computers

Portable Data-Collection Equipment

Personal Data Communicators/Computers

Medical Instrumentation

2-Cell & 3-Cell Battery-Operated Equipment

Glucose Meters

__________Typical Operating Circuit

____________________________Features

Operates Down to 0.7V Input Supply Voltage

87% Efficiency at 200mA

60µA Quiescent Current

20µA Shutdown Mode with Active Reference and

LBI Detector

500kHz Maximum Switching Frequency

±1.5% Reference Tolerance Over Temperature

Low-Battery Detector (LBI/LBO)

8-Pin DIP and SO Packages

______________Ordering Information

PART

MAX756

CPA

MAX756CSA

MAX756C/D

MAX756EPA

MAX756ESA

MAX757

CPA

MAX757CSA

MAX757C/D

MAX757EPA

MAX757ESA

TEMP. RANGE

0°C to +70°C

0°C to +70°C

0°C to +70°C

-40°C to +85°C

-40°C to +85°C

0°C to +70°C

0°C to +70°C

0°C to +70°C

-40°C to +85°C

-40°C to +85°C

* Dice are tested at T

A

= +25°C only.

PIN-PACKAGE

8 Plastic DIP

8 SO

Dice*

8 Plastic DIP

8 SO

8 Plastic DIP

8 SO

Dice*

8 Plastic DIP

8 SO

_________________Pin Configurations

1

SHDN

5

LBI

150

µ

F

LX

8

2

3/5

MAX756

OUT

6

INPUT

2V to V

OUT

22

µ

H

1N5817

OUTPUT

5V at 200mA or

3.3V at 300mA

100

µ

F

0.1

µ

F

3

REF

7

GND

LBO

4

LOW-BATTERY

DETECTOR OUTPUT

TOP VIEW

SHDN

3/5

REF

3

LBO

4

1

2

MAX756

DIP/SO

6

5

8

7

LX

GND

OUT

LBI

SHDN

REF

LBO

1

FB

2

3

4

MAX757

DIP/SO

8

7

LX

GND

6

OUT

5

LBI

________________________________________________________________ Maxim Integrated Products 1

Call toll free 1-800-998-8800 for free samples or literature.

3.3V/5V/Adjustable-Output,

Step-Up DC-DC Converters

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (OUT to GND) ....................................-0.3V, +7V

Switch Voltage (LX to GND) ........................................-0.3V, +7V

Auxiliary Pin Voltages (SHDN, LBI, LBO, REF,

3/5, FB to GND) ........................................-0.3V, (V

OUT

+ 0.3V)

Reference Current (I

REF

) ....................................................2.5mA

Continuous Power Dissipation (T

A

= +70°C)

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

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

Operating Temperature Ranges:

MAX75_C_ _ ........................................................0°C to +70°C

MAX75_E_ _......................................................-40°C to +85°C

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

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

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

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.

ELECTRICAL CHARACTERISTICS

(Circuits of Figure 1 and Typical Operating Circuit, V

IN

= 2.5V, I

LOAD

= 0mA, T

A

= T

MIN to T

MAX

, unless otherwise noted.)

PARAMETER

Output Voltage

2V < V

IN

< 3V

CONDITIONS

MAX756, 3/5 = 0V, 0mA < I

LOAD

< 200mA

MAX756, 3/5 = 3V, 0mA < I

LOAD

< 300mA

MAX757, V

OUT

= 5V, 0mA < I

LOAD

< 200mA

I

LOAD

= 10mA Minimum Start-Up Supply Voltage

Minimum Operating Supply

Voltage (once started)

I

LOAD

= 20mA

Quiescent Supply Current in

3.3V Mode (Note 1)

I

LOAD

= 0mA, 3/5 = 3V, LBI = 1.25V, V

FB = 1.3V (MAX757 only)

OUT

= 3.47V,

MIN

4.8

3.17

4.8

TYP

5.0

3.30

5.0

1.1

0.7

MAX

5.2

3.43

5.2

1.8

60

Battery Quiescent Current

Measured at V

IN in Figure 1

Shutdown Quiescent Current

(Note 1)

Reference Voltage

Reference-Voltage Regulation

LBI Input Threshold

LBI Input Hysteresis

LBO Output Voltage Low

LBO Output Leakage Current

SHDN, 3/5 Input Voltage Low

SHDN, 3/5 Input Voltage High

SHDN, 3/5, FB, LBI Input Current

FB Voltage

Output Voltage Range

Output set for 3.3V

SHDN = 0V, LBI = 1.25V, 3/5 = 3V, V

OUT

FB = 1.3V (MAX757 only)

I

No REF load, C

REF

= 0.1µF

= 3.47V,

3/5 = 3V, -20µA < REF load < 250µA, C

REF

= 0.22µF

With falling edge

SINK

= 2mA

LBO = 5V

LBI = 1.25V, FB = 1.25V, SHDN = 0V or 3V,

3/5 = 0V or 3V

MAX757

MAX757, I

LOAD

= 0mA (Note 2)

1.23

1.22

1.6

1.22

2.7

60

20

1.25

0.8

1.25

25

1.25

40

1.27

2.0

1.28

0.4

1

0.4

±100

1.28

5.5

UNITS

V

µA

µA nA

V

V

µA

V

%

V mV

V

µA

V

V

V

V

Note 1:

Supply current from the 3.3V output is measured with an ammeter between the 3.3V output and OUT pin. This current correlates directly with actual battery supply current, but is reduced in value according to the step-up ratio and efficiency.

Note 2:

Minimum value is production tested. Maximum value is guaranteed by design and is not production tested.

2 _______________________________________________________________________________________

3.3V/5V/Adjustable-Output,

Step-Up DC-DC Converters

__________________________________________Typical Operating Characteristics

(Circuit of Figure 1, T

A

= +25°C, unless otherwise noted.)

90

80

70

60

50

40

0.1

1M

100k

EFFICIENCY vs. LOAD CURRENT

3.3V OUTPUT MODE

V

IN

= 2.0V

V

IN

= 1.2V

1 10

LOAD CURRENT (mA)

100

SWITCHING FREQUENCY vs. LOAD CURRENT

1000

5V MODE

90

80

70

60

50

40

0.1

500

400

EFFICIENCY vs. LOAD CURRENT

5V OUTPUT MODE

V

IN

= 3.3V

V

IN

= 2.5V

V

IN

= 1.25V

1 10

LOAD CURRENT (mA)

100

QUIESCENT CURRENT vs. INPUT VOLTAGE

CURRENT MEASURED AT V

IN

1000

MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE

800

700

600

500

400

300

200

100

0

0

3.3V MODE

5V MODE

1

2

3

INPUT VOLTAGE (V)

4

SHUTDOWN QUIESCENT CURRENT vs. INPUT VOLTAGE

50

5

CURRENT MEASURED AT V

IN

40

30

10k

300

V

OUT

= 5V

3.3V MODE

1k

200

20

10

100

10

10

µ

100

V

IN

= 2.5V

100

µ

1m 10m

LOAD CURRENT (A)

100m 1

0

1

1.8

MINIMUM START-UP INPUT VOLTAGE vs. LOAD CURRENT

V

OUT

= 3.3V

2 3

INPUT VOLTAGE (V)

4

10

5

0

1 2 3

INPUT VOLTAGE (V)

4

REFERENCE VOLTAGE

LOAD REGULATION

5

1.6

1.4

8

6

1.2

1.0

0.8

1

3.3V MODE

10 100

LOAD CURRENT (mA)

1000

4

2

0

0

V

OUT

= 3.3V

50 100 150

LOAD CURRENT (

µ

A)

200

250

_________________________________________________________________________________________________ 3

3.3V/5V/Adjustable-Output,

Step-Up DC-DC Converters

_____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1, T

A

= +25°C, unless otherwise noted.)

LOAD-TRANSIENT RESPONSE START-UP DELAY

OUTPUT

VOLTAGE

50mV/div

V

SHDN

2V/div

3V

0V

5V

OUTPUT

CURRENT

0mA to 200mA

V

IN

= 2.5V

HORIZONTAL = 50

µ s/div

5V Mode

V

OUT

2V/div

V

IN

= 2.5V

HORIZONTAL = 5ms/div

5V Mode

0V

______________________________________________________________Pin Description

PIN

MAX756 MAX757

NAME FUNCTION

1

2

3

4

5

6

7

8

1

2

3

4

5

6

7

8

SHDN

3/5

FB

REF

LBO

LBI

OUT

GND

LX

Shutdown Input disables SMPS when low, but the voltage reference and low-battery comparator remain active.

Selects the main output voltage setting; 5V when low, 3.3V when high.

Feedback Input for adjustable output operation. Connect to an external voltage divider between OUT and GND.

1.25V Reference Voltage Output. Bypass with 0.22µF to GND (0.1µF if there is no external reference load). Maximum load capability is 250µA source, 20µA sink.

Low-Battery Output. An open-drain N-channel MOSFET sinks current when the voltage at

LBI drops below +1.25V.

Low-Battery Input. When the voltage on LBI drops below +1.25V, LBO sinks current.

Connect to V

IN if not used.

Connect OUT to the regulator output. It provides bootstrapped power to both devices, and also senses the output voltage for the MAX756.

Power Ground. Must be low impedance; solder directly to ground plane.

1A, 0.5

N-Channel Power MOSFET Drain

4 _______________________________________________________________________________________

3.3V/5V/Adjustable-Output,

Step-Up DC-DC Converters

_______________Detailed Description

Operating Principle

The MAX756/MAX757 combine a switch-mode regulator with an N-channel MOSFET, precision voltage reference, and power-fail detector in a single monolithic device.

The MOSFET is a “sense-FET” type for best efficiency, and has a very low gate threshold voltage to ensure start-up under low-battery voltage conditions (1.1V typ).

Pulse-Frequency

Modulation Control Scheme

A unique minimum off time, current-limited, pulse-frequency modulation (PFM) control scheme is a key feature of the MAX756/MAX757. This PFM scheme combines the advantages of pulse-width modulation (PWM) (high output power and efficiency) with those of a traditional PFM pulse-skipper (ultra-low quiescent currents). There is no oscillator; at heavy loads, switching is accomplished through a constant peak-current limit in the switch, which allows the inductor current to self-oscillate between this peak limit and some lesser value. At light loads, switching frequency is governed by a pair of one-shots, which set a minimum off-time (1µs) and a maximum on-time (4µs).

The switching frequency depends on the load and the input voltage, and can range as high as 500kHz.

The peak switch current of the internal MOSFET power switch is fixed at 1A ±0.2A. The switch's on resistance is typically 0.5

, resulting in a switch voltage drop

(V

SW

) of about 500mV under high output loads. The value of V

SW decreases with light current loads.

Conventional PWM converters generate constant-frequency switching noise, whereas this architecture produces variable-frequency switching noise. However, the noise does not exceed the switch current limit times the filter-capacitor equivalent series resistance (ESR), unlike conventional pulse-skippers.

Voltage Reference

The precision voltage reference is suitable for driving external loads such as an analog-to-digital converter.

It has guaranteed 250µA source-current and 20µA sink-current capability. The reference is kept alive even in shutdown mode. If the reference drives an external load, bypass it with 0.22µF to GND. If the reference is unloaded, bypass it with at least 0.1µF.

Control-Logic Inputs

The control inputs (3/5, SHDN) are high-impedance

MOS gates protected against ESD damage by normally reverse-biased clamp diodes. If these inputs are driven from signal sources that exceed the main supply voltage, the diode current should be limited by a series resistor (1M

Ω suggested). The logic input threshold level is the same (approximately 1V) in both 3.3V and

5V modes. Do not leave the control inputs floating.

__________________Design Procedure

Output Voltage Selection

The MAX756 output voltage can be selected to 3.3V or

5V under logic control, or it can be left in one mode or the other by tying 3/5 to GND or OUT. Efficiency varies depending upon the battery and the load, and is typically better than 80% over a 2mA to 200mA load range.

The device is internally bootstrapped, with power derived from the output voltage (via OUT). When the output is set at 5V instead of 3.3V, the higher internal supply voltage results in lower switch-transistor on resistance and slightly greater output power.

Bootstrapping allows the battery voltage to sag to less than 1V once the system is started. Therefore, the battery voltage range is from V

OUT

(where V

D

+ V

D to less than 1V is the forward drop of the Schottky rectifier).

If the battery voltage exceeds the programmed output voltage, the output will follow the battery voltage. In many systems this is acceptable; however, the output voltage must not be forced above 7V.

The output voltage of the MAX757 is set by two resistors, R1 and R2 (Figure 1), which form a voltage divider between the output and the FB pin. The output voltage is set by the equation:

V

OUT

= (V

REF

) [(R2 + R1) / R2] where V

REF

= 1.25V.

To simplify resistor selection:

R1 = (R2) [(V

OUT

/ V

REF

) - 1]

Since the input bias current at FB has a maximum value of 100nA, large values (10k

Ω to 200k

) can be used for R1 and R2 with no significant loss of accuracy.

For 1% error, the current through R1 should be at least

100 times FB’s bias current.

Low-Battery Detection

The MAX756/MAX757 contain on-chip circuitry for lowbattery detection. If the voltage at LBI falls below the regulator’s internal reference voltage (1.25V), LBO (an opendrain output) sinks current to GND. The low-battery monitor's threshold is set by two resistors, R3 and R4 (Figure

1), which forms a voltage divider between the input voltage and the LBI pin. The threshold voltage is set by R3 and R4 using the following equation:

R3 = [(V

IN

/ V

REF

) - 1] (R4)

_______________________________________________________________________________________ 5

3.3V/5V/Adjustable-Output,

Step-Up DC-DC Converters

R3

R4

C3

0.1

µ

F

C1

150

µ

F

5

LBI

1

SHDN

3

REF

LX

8

MAX757

OUT

6

FB

2

LBO

4

7

GND

Figure 1. Standard Application Circuit

V

IN

L1

22

µ

H

D1

1N5817

R1

R2

V

OUT

C2

100

µ

F where V

IN is the desired threshold of the low-battery detector, R3 and R4 are the input divider resistors at

LBI, and V

REF is the internal 1.25V reference.

Since the LBI current is less than 100nA, large resistor values (typically 10k

Ω to 200k

) can be used for R3 and R4 to minimize loading of the input supply.

When the voltage at LBI is below the internal threshold,

LBO sinks current to GND. A pull-up resistor of 10k

Ω or more connected from LBO to V

OUT can be used when driving CMOS circuits. Any pull-up resistor connected to LBO should not be returned to a voltage source greater than V

OUT

. When LBI is above the threshold, the LBO output is off. The low-battery comparator and reference voltage remain active when the

MAX756/MAX757 is in shutdown mode.

If the low-battery comparator is not used, connect LBI to V

IN and leave LBO open.

Inductor Selection

The inductors should have a saturation (incremental) current rating equal to or greater than the peak switchcurrent limit, which is 1.2A worst-case. However, it’s generally acceptable to bias the inductor into saturation by 20%, although this will reduce the efficiency.

The 22µH inductor shown in the typical applications circuit is sufficient for most MAX756/MAX757 application circuits. Higher input voltages increase the energy transferred with each cycle, due to the reduced input/output differential. Minimize excess ripple due to increased energy transfer by reducing the inductor value (10µH suggested).

The inductor’s DC resistance significantly affects efficiency. For highest efficiency, limit L1’s DC resistance to 0.03

Ω or less. See Table 1 for a list of suggested inductor suppliers.

Table 1. Component Suppliers

INDUCTORS CAPACITORS PRODUCTION

METHOD

Surface-Mount AVX

TPS series

Miniature

Through-Hole

Sumida

CD54-220 (22µH)

CoilCraft

DT3316-223

Coiltronics

CTX20-1

Sumida

RCH654-220

Sprague

595D series

Low-Cost

Through-Hole

CoilCraft

PCH-27-223

Sanyo OS-CON

OS-CON series low-ESR organic semiconductor

Nichicon

PL series low-ESR electrolyic

United Chemi-Con

LXF series

AVX

Nihon

USA: (207) 282-5111, FAX (207) 283-1941

(800) 282-9975

USA: (708) 639-6400, FAX (708) 639-1969 CoilCraft

Coiltronics USA: (407) 241-7876, FAX (407) 241-9339

Collmer

Semiconductor USA: (214) 233-1589

Motorola USA: (602) 244-3576, FAX (602) 244-4015

Nichicon USA: (708) 843-7500, FAX (708) 843-2798

Japan: +81-7-5231-8461, FAX (+81-) 7-5256-4158

USA: (805) 867-2555, FAX (805) 867-2556

Japan: +81-3-3494-7411, FAX (+81-) 3-3494-7414

Sanyo OS-CON USA: (619) 661-6835

Japan: +81-720-70-1005, FAX (+81-720-) 70-1174

Sprague

Sumida

USA:

USA:

(603) 224-1961, FAX (603) 224-1430

(708) 956-0666

Japan: +81-3-3607-5111, FAX (+81-3-) 3607-5428

United

Chemi-Con USA: (708) 696-2000, FAX (708) 640-6311

Capacitor Selection

A 100µF, 10V surface-mount (SMT) tantalum capacitor typically provides 50mV output ripple when stepping up from 2V to 5V at 200mA. Smaller capacitors, down to 10µF, are acceptable for light loads or in applications that can tolerate higher output ripple.

6 _______________________________________________________________________________________

The ESR of both bypass and filter capacitors affects efficiency. Best performance is obtained by using specialized low-ESR capacitors, or connecting two or more filter capacitors in parallel. The smallest low-ESR SMT tantalum capacitors currently available are Sprague

595D series, which are about half the size of competing products. Sanyo OS-CON organic semiconductor through-hole capacitors also exhibit very low ESR, and are especially useful for operation at cold temperatures. Table 1 lists suggested capacitor suppliers.

3.3V/5V/Adjustable-Output,

Step-Up DC-DC Converters

Rectifier Diode

For optimum performance, a switching Schottky diode, such as the 1N5817, is recommended. 1N5817 equivalent diodes are also available in surface-mount packages from Collmer Semiconductor in Dallas, TX, phone

(214) 233-1589. The part numbers are SE014 or

SE024. For low output power applications, a pn junction switching diode, such as the 1N4148, will also work well, although efficiency will suffer due to the greater forward voltage drop of the pn junction diode.

SHDN

3/5

MINIMUM

OFF-TIME

ONE-SHOT

Q

ONE-SHOT

TRIG

F/F

S Q

R

MAXIMUM

ON-TIME

ONE-SHOT

TRIG

ONE-SHOT

Q

MAX756

N

LX

V

IN

V

OUT

GND

OUT

LBO

LBI

N

REFERENCE

REF

Figure 2. MAX756 Block Diagram

_______________________________________________________________________________________ 7

PC Layout and Grounding

The MAX756/MAX757 high peak currents and high-frequency operation make PC layout important for minimizing ground bounce and noise. The distance between the MAX756/MAX757’s GND pin and the ground leads of C1 and C2 in Figure 1 must be kept to less than 0.2" (5mm). All connections to the FB and LX pins should also be kept as short as possible. To obtain maximum output power and efficiency and minimum output ripple voltage, use a ground plane and solder the MAX756/MAX757 GND (pin 7) directly to the ground plane.

___________________Chip Topography

3/5 (MAX756)

FB (MAX757)

SHDN

LX

REF

GND

0.122"

(3.10mm)

GND

OUT

LBI

LBO

0.080"

(2.03mm)

TRANSISTOR COUNT: 758

SUBSTRATE CONNECTED TO OUT

________________________________________________________Package Information

E H

DIM

A

A1

B

C

D

E e

H h

L

α

INCHES

MIN

0.053

0.004

0.014

0.007

MAX

0.069

0.010

0.019

0.010

0.189

0.150

0.197

0.157

0.050 BSC

0.228

0.010

0.016

0.244

0.020

0.050

MILLIMETERS

MIN

1.35

0.10

0.35

0.19

MAX

1.75

0.25

0.49

0.25

4.80

3.80

5.00

4.00

1.27 BSC

5.80

0.25

0.40

6.20

0.50

1.27

21-325A

D h x 45˚

α

A e

A1

0.127mm

0.004in.

C

L

8-PIN PLASTIC

SMALL-OUTLINE

PACKAGE

B

8 _______________________________________________________________________________________

19-2902; Rev 0; 7/03

SOT23 Dual-Input USB/AC Adapter 1-Cell Li+

Battery Chargers

General Description

The MAX1551/MAX1555 charge a single-cell lithium-ion

(Li+) battery from both USB* and AC adapter sources.

They operate with no external FETs or diodes, and accept operating input voltages up to 7V.

On-chip thermal limiting simplifies PC board layout and allows optimum charging rate without the thermal limits imposed by worst-case battery and input voltage. When the MAX1551/MAX1555 thermal limits are reached, the chargers do not shut down, but progressively reduce charging current.

The MAX1551 includes a POK output to indicate when input power is present. If either charging source is active, POK goes low. The MAX1555 instead features a

CHG output to indicate charging status.

With USB connected, but without DC power, charge current is set to 100mA (max). This allows charging from both powered and unpowered USB hubs with no port communication required. When DC power is connected, charging current is set at 280mA (typ). No input-blocking diodes are required to prevent battery drain.

The MAX1551/MAX1555 are available in 5-pin thin SOT23 packages and operate over a -40°C to +85°C range.

Applications

Features

Charge from USB or AC Adapter

Automatic Switchover when AC Adapter is

Plugged In

On-Chip Thermal Limiting Simplifies Board

Design

Charge Status Indicator

5-Pin Thin SOT23 Package

Protected by U.S. Patent #6,507,172

PART

MAX1551EZK-T

MAX1555EZK-T

PART

MAX1551EZK

MAX1555EZK

Ordering Information

TEMP RANGE

-40°C to +85°C

-40°C to +85°C

PIN-PACKAGE

5 Thin SOT23-5

5 Thin SOT23-5

TOP MARK

ADRT

ADRU

Selector Guide

FEATURES

POK Output

CHG Output

PDAs

Wireless Appliances

Cell Phones

Digital Cameras

Pin Configuration Typical Operating Circuit

TOP VIEW

AC ADAPTER

3.7V TO 7V

DC BAT

Li+

TO SYSTEM

LOAD

USB 1

GND

2

MAX1551

(MAX1555)

5 BAT

POK

(CHG)

3

THIN SOT23

4 DC

CHARGE

CONTROL

USB

3.7V TO 6V

USB

MAX1551

(MAX1555)

LOGIC

CONTROL

POK

(CHG)

GND

TO LOGIC RAIL

*Protected by U.S. Patent #6,507,172.

________________________________________________________________ Maxim Integrated Products 1

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.

SOT23 Dual-Input USB/AC Adapter 1-Cell Li+

Battery Chargers

ABSOLUTE MAXIMUM RATINGS

DC to GND......................................................................0 to +8V

DC to BAT .......................................................................0 to +7V

BAT, CHG, POK, USB to GND .................................-0.3V to +7V

Continuous Power Dissipation (T

A

= +70

°C)

5-Pin Thin SOT23 (derate 9.1mW/

°C above +70°C)....727mW

Operating Temperature Range ...........................-40

°C to +85°C

Junction Temperature Range ............................-40

°C to +150°C

Storage Temperature Range .............................-65

°C to +150°C

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

°C

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.

ELECTRICAL CHARACTERISTICS

(V

DC

= 5V, V

USB

= 0, I

BAT

= 0, C

BAT

= 1µF, T

A

= 0°C to +85°C, unless otherwise noted.)

PARAMETER

DC

DC Voltage Range

DC to BAT Voltage Range

(Note 1)

CONDITIONS

DC Undervoltage Lockout

Threshold

DC Supply Current

DC to BAT On-Resistance

Input rising, 430mV hysteresis, V

BAT

= 3V (Note 1)

DC to BAT Dropout Voltage

V

DC

= 3.7V, V

BAT

= 3.6V

When charging stops, V

BAT

= 4V,

DC falling, 200mV hysteresis

USB

USB Voltage Range

USB Undervoltage Threshold

USB Supply Current

USB to BAT On-Resistance

USB to BAT Dropout Voltage

(Note 1)

Input rising, 430mV hysteresis, V

DC

= 0,

V

BAT

= 3V (Note 1)

V

USB

= 5V, V

DC

= 0

V

USB

= 3.7V, V

BAT

= 3.6V, V

DC

= 0

When charging stops, V

BAT

= 4V,

USB falling, 200mV hysteresis, V

DC

= 0

BAT

BAT Regulation Voltage

DC Charging Current

V

DC

or V

USB

= 5V

V

BAT

= 3.3V, V

USB

= 0, V

DC

= 5V

USB Charging Current V

BAT

= 3.3V, V

DC

= 0, V

USB

= 5V

BAT Prequal Threshold V

BAT

rising, 100mV hysteresis

Prequalification Charging Current V

BAT

= 2.8V

BAT Leakage Current

POK, CHG, AND THERMAL LIMIT

V

DC

= V

USB

= 0, V

BAT

= 4.2V

CHG Threshold

Charge current where

CHG goes high,

I

BAT

falling, 50mA hysteresis

CHG, POK Logic-Low Output

CHG, POK Leakage Current

Thermal-Limit Temperature

I

CHG

V

CHG

, I

POK

, V

= 10mA

POK

= 6V, T

A

= +25

°C

Charge current reduced by 17mA/

°C above this temperature

MIN

3.7

0.1

3.75

30

3.7

3.75

30

4.158

220

80

2.9

20

25

TYP

3.95

1.75

1

60

3.95

1.65

2

60

4.2

280

90

3

40

50

150

0.001

+110

MAX

7.0

6.0

4.15

3

2

90

6.0

4.15

3

4

90

4.242

340

100

3.1

80

5

100

300

1

UNITS

V

V

V mA

Ω mV

V

V mA

Ω mV

V mA mA

V mA

µA mA mV

µA

°C

2 _______________________________________________________________________________________

SOT23 Dual-Input USB/AC Adapter 1-Cell Li+

Battery Chargers

ELECTRICAL CHARACTERISTICS

(V

DC

= 5V, V

USB

= 0, I

BAT

= 0, C

BAT

= 1µF, T

A

= -40°C to +85°C, unless otherwise noted.) (Note 2)

PARAMETER

DC

DC Voltage Range

DC to BAT Voltage Range

(Note 1)

CONDITIONS

DC Undervoltage Lockout

Threshold

DC Supply Current

DC to BAT On-Resistance

Input rising, 430mV hysteresis, V

BAT

= 3V (Note 1)

DC to BAT Dropout Voltage

V

DC

= 3.7V, V

BAT

= 3.6V

When charging stops, V

BAT

= 4V, DC falling, 200mV hysteresis

USB

USB Voltage Range (Note 1)

USB Undervoltage Lockout

Threshold

Input rising, 430mV hysteresis, V

DC

= 0, V

BAT

= 3V

(Note 1)

USB Supply Current

USB to BAT On-Resistance

USB to BAT Dropout Voltage

V

USB

= 5V, V

DC

= 0

V

USB

= 3.7V, V

BAT

= 3.6V, V

DC

= 0

When charging stops, V

BAT

= 4V, USB falling, 200mV hysteresis, V

DC

= 0

BAT

BAT Regulation Voltage

DC Charging Current

V

DC

or V

USB

= 5V

V

BAT

= 3.3V, V

USB

= 0, V

DC

= 5V

USB Charging Current

BAT Leakage Current

POK, CHG

V

BAT

= 3.3V, V

DC

= 0, V

USB

= 5V

BAT Prequal Threshold V

BAT

rising, 100mV hysteresis

Prequalification Charging Current V

BAT

= 2.8V

V

DC

= V

USB

= 0, V

BAT

= 4.2V

CHG Threshold

Charge current where

CHG goes high,

I

BAT

falling, 50mA hysteresis

CHG, POK Logic-Low Output

CHG, POK Leakage Current

I

CHG

V

CHG

, I

POK

, V

= 10mA

POK

= 6V, T

A

= +25

°C

MIN

3.7

0.1

3.75

30

3.7

3.75

30

4.141

220

80

2.9

20

25

MAX

7.0

6.0

4.15

3

2

95

6.0

4.15

3

4

95

4.259

340

100

3.1

80

5

100

300

1

UNITS

V

V

V mA

Ω mV

V

V mA

Ω mV mA mV

µA

Note 1: The input undervoltage lockout has 430mV of hysteresis. The charger turns on when an input rises to 3.95V (typ), and turns off when it falls below 3.52V.

Note 2: Specifications to -40

°C are guaranteed by design, not production tested.

V mA mA

V mA

µA

_______________________________________________________________________________________ 3

SOT23 Dual-Input USB/AC Adapter 1-Cell Li+

Battery Chargers

Typical Operating Characteristics

(V

DC

= 5V, V

USB

= 0, I

BAT

= 0, C

BAT

= 1µF, T

A

= +25

°C, unless otherwise noted.)

CHARGE CURRENT vs. DC VOLTAGE HEADROOM

CHARGE CURRENT vs. USB VOLTAGE HEADROOM

DC CHARGE CURRENT vs. BATTERY VOLTAGE

300

250

200

100

80

60

300

250

200

150 150

100

50

0

V

BAT

= 3.8V, V

DC

FALLING

-50

0 0.1

0.2

0.3

0.4

DC VOLTAGE HEADROOM (V

DC

- V

BAT

) (V)

0.5

40

20

0

V

DC

= 0, V

BAT

= 3.8V, V

USB

FALLING

-20

0 0.1

0.2

0.3

0.4

USB VOLTAGE HEADROOM (V

USB

- V

BAT

) (V)

0.5

100

50

0

-50

0 0.5

1.0

1.5

2.0

2.5

3.0

BATTERY VOLTAGE (V)

3.5

4.0

4.5

USB CHARGE CURRENT vs. BATTERY VOLTAGE

DC CHARGE CURRENT vs. AMBIENT TEMPERATURE

BATTERY TERMINATION VOLTAGE vs. TEMPERATURE

100

300

80

250

THERMAL LIMIT ACTIVATED

200

60

150

40

100

20

50

0

-20

0 0.5

1.0

1.5

2.0

2.5

3.0

BATTERY VOLTAGE (V)

3.5

4.0

4.5

0

-50

25

V

BAT

= 3.8V, V

DC

= 5V

35 45 55 65

TEMPERATURE (

°C)

OFF-BATTERY LEAKAGE CURRENT vs. DC INPUT VOLTAGE

2.5

2.0

V

DC

= 0, SWEEPING USB

0 TO 5V OR V

USB

= 0,

SWEEPING DC 0 TO 5V

V

BAT

= 4.2V

1.5

75

0A

0V

1.0

85

4.22

4.21

4.20

4.19

4.18

-40

BAT OPEN

-15 10 35

TEMPERATURE (

°C)

60

USB-TO-DC TRANSITION WAVEFORM

MAX1551/55 toc08

BATTERY

CURRENT

200mA/div

V

USB

5V/div

85

0.5

0V

V

POK

2V/div

V

DC

5V/div

0

0 1 2 3 4

DC OR USB INPUT VOLTAGE (V)

5

0V

400ms/div

4 _______________________________________________________________________________________

PIN

1

2

3

4

5

SOT23 Dual-Input USB/AC Adapter 1-Cell Li+

Battery Chargers

Pin Description

NAME FUNCTION

USB

DC

USB Port Charger Supply Input. USB draws up to 100mA to charge the battery. Decouple USB with a 1µF ceramic capacitor to GND.

GND Ground

POK

Power-OK Active-Low Open-Drain Charger Status Indicator.

POK pulls low when either charger source is present (MAX1551 only).

CHG

Active-Low Open-Drain Charge Status Indicator.

CHG pulls low when the battery is charging. CHG goes to a high-impedance state, indicating the battery is fully charged, when the charger is in voltage mode and charge current falls below 50mA.

CHG is high impedance when both input sources are low (MAX1555 only).

DC Charger Supply Input for an AC Adapter. DC draws 280mA to charge the battery. Decouple DC with a

1µF ceramic capacitor to GND.

BAT Battery Connection. Decouple BAT with a 1µF ceramic capacitor to GND.

Detailed Description

The MAX1551/MAX1555 charge a single-cell Li+ battery from both USB and AC adapter sources, enabling portable users to forgo carrying a wall cube. These devices operate with no external FETs or diodes, and accept operating input voltages up to 7V.

An internal thermal control loop simplifies PC board layout and allows optimum charging rate without the thermal limits imposed by worst-case battery and input voltage. When the MAX1551/MAX1555 thermal limits are reached, the chargers do not shut down, but simply reduce charging current by 17mA/

°C above a die temperature of +110

°C.

With USB connected, but without DC power, the charge current is set to 100mA (max). This allows charging from both powered and unpowered USB hubs with no port communication required. When DC power is connected, charging current is set at 280mA (typ). The

MAX1551/MAX1555 do not feature an enable input.

Once power is connected to USB and/or DC, the charger is on.

When input power is removed, battery leakage current is less than 5µA. No input-blocking diodes are required to prevent battery drain. Insert a diode at DC (the adapter input) if protection from negative voltage inputs

(reversed-polarity adapter plugs) is required.

Table 1. USB and DC Input Selection

V

DC

> 7V OR V

USB

> 6V

Exceeds operating input range. Not allowed. See the

Absolute Maximum Ratings section.

(V

DC takes precedence when both inputs are present.)

USB to Adapter Power Handoff

The MAX1551/MAX1555 can charge from either the

USB input or the DC input. The battery does not charge from both sources at the same time. The MAX1551/

MAX1555 automatically detect the active input and charge from that. If both power sources are active, the

DC input takes precedence. The switchover between

DC and USB is detailed in Table 1.

MAX1551 Power-OK (

POK)

The MAX1551’s POK is an active-low, open-drain output that goes low when V

DC or V

USB is above 3.95V.

POK can be used as a logic output or can drive an

LED. POK indicates the charger is connected to input power and is charging.

MAX1555 Charge Status (

CHG)

The MAX1555’s CHG is an active-low, open-drain charge status indicator. CHG pulls low when the battery is charging (whenever USB or DC are powered) and charge current is greater than 50mA. CHG indicates when the battery is fully charged by going high impedance when the charger is in voltage mode and charge current falls below 50mA. Charging does not stop when

CHG goes high. CHG is low in precharge mode.

V

DC

> 3.95V AND

V

USB

DON’T CARE

280mA (typ) charging from DC

V

DC

< 3.52V AND

3.95V < V

USB

< 6V

100mA (max) charging from USB

V

DC

AND V

USB

< 3.52V

Undervoltage lockout

_______________________________________________________________________________________ 5

SOT23 Dual-Input USB/AC Adapter 1-Cell Li+

Battery Chargers

Precharge Current

The MAX1551/MAX1555 feature a precharge current to protect deeply discharged cells. If V

BAT is less than 3V, the device enters precharge mode where charging current is limited to 40mA.

Package Thermal Limiting

On-chip thermal limiting in the MAX1551/MAX1555 simplifies PC board layout and allows charging rates to be optimized without the limits imposed by worst-case battery and input voltages. The device reduces the power dissipation at BAT to prevent overheating. This allows the board design to be optimized for compact size and typical thermal conditions. When the MAX1551/

MAX1555 thermal limits are reached, the chargers do not shut down, but progressively reduce charging current by 17mA/

°C above a die temperature of +110°C.

Solder the MAX1551/MAX1555s’ GND to a large ground plane to help dissipate power and keep the die temperature below the thermal limit. The USB charge current of 100mA is unlikely to induce thermal limiting.

Bypass Capacitors

Use ceramic bypass capacitors at DC, USB, and BAT.

Mount these capacitors within 1cm of their respective pins. X7R and X5R dielectrics are recommended.

Chip Information

TRANSISTOR COUNT: 541

PROCESS: BiCMOS

Typical Application Circuit

AC ADAPTER

3.7V TO 7V

C1

1

µF

USB

3.7V TO 6V

C2

1

µF

DC

USB

MAX1551

(MAX1555)

CHARGE

CONTROL

BAT

LOGIC

CONTROL

POK

(CHG)

GND

C3

1

µF

Li+

TO SYSTEM

LOAD

TO LOGIC RAIL

R1

100k

INDICATES

THAT POWER

IS PRESENT

(EITHER DC

OR USB)

6 _______________________________________________________________________________________

SOT23 Dual-Input USB/AC Adapter 1-Cell Li+

Battery Chargers

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to

www.maxim-ic.com/packages

.)

_______________________________________________________________________________________ 7

SOT23 Dual-Input USB/AC Adapter 1-Cell Li+

Battery Chargers

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to

www.maxim-ic.com/packages

.)

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

19-2024; Rev 2; 6/03

USB-Powered Li+ Charger

General Description

The MAX1811 is a single-cell lithium-ion (Li+) battery charger that can be powered directly from a USB port* or from an external supply up to 6.5V. It has a 0.5% overall battery regulation voltage accuracy to allow maximum utilization of the battery capacity.

The charger uses an internal FET to deliver up to

500mA charging current to the battery. The device can be configured for either a 4.1V or 4.2V battery, using the SELV input. The SELI input sets the charge current to either 100mA or 500mA. An open-drain output (CHG) indicates charge status.

The MAX1811 has preconditioning that soft-starts a near-dead battery cell before charging. Other safety features include continuous monitoring of voltage and current and initial checking for fault conditions before charging.

The MAX1811 is available in a small 1.4W thermally enhanced 8-pin SO package.

Features

Charges Single-Cell Li+ Batteries Directly from

USB Port

0.5% Overall Charging Accuracy

Minimal External Components

Input Diode Not Required

Automatic IC Thermal Regulation

Preconditions Near-Depleted Cells

Convenient Power SO-8 Package (1.4W)

Protected by U.S. Patent # 6,507,172

________________________Applications

PDAs and Palmtops

Digital Still Cameras

MP3 Players

Cell Phones

Two-Way Pagers

Hand-Held Computers

PART

MAX1811ESA

Ordering Information

TEMP RANGE

-40°C to +85°C

PIN-PACKAGE

8 SO

Typical Operating Circuit Pin Configuration

TOP VIEW

4.35V TO 6.5V

4.2V

4.1V

ON

OFF

500mA

100mA

IN

SELV

EN

SELI

MAX1811

BATT

CHG

GND

LED

TO LOAD

SINGLE

Li+

CELL

TO IN

CHG

LOGIC OUT

SELV 1

SELI 2

GND 3

IN 4

MAX1811

8 CHG

7 EN

6 GND

5 BATT

SO

* Protected by U.S. Patent # 6,507,172

________________________________________________________________ Maxim Integrated Products 1

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.

USB-Powered Li+ Charger

ABSOLUTE MAXIMUM RATINGS

IN, BATT, SELI, CHG, EN to GND ..............................-0.3V to 7V

SELV to GND ...............................................-0.3V to (V

IN

+ 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

8-Pin SO (derate 17.5mW/°C above +70°C)....................1.4W

Short-Circuit Duration.................................................Continuous

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

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

Maximum Die Temperature..............................................+150°C

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

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.

ELECTRICAL CHARACTERISTICS

(V

IN

= 4.5V, EN = IN, T

A

= 0°C to +85°C, unless otherwise noted.)

CONDITIONS PARAMETER

Input Supply Voltage

Input Undervoltage Lockout

Input Undervoltage Lockout Hysteresis

I

IN

rising

Input Supply Current

Charging Headroom

Precondition Threshold

Operating, EN = IN, no load

Shutdown, EN = GND

SELI = GND (100mA mode),

V

IN

= 4.35V

SELI = IN (500mA mode)

BATT rising, transition from precondition to charge mode

Precondition Threshold Hysteresis

CHG Output Leakage Current

CHG Output Low Voltage

Charging Current

BATT Regulation Voltage

V

IN

= V

CHG

= 6.5V

I

SINK

= 10mA

V

SELI

= V

IN

= 5.5V, V

BATT

= 2.7V

SELI = GND, V

IN

= 5.5V, V

BATT

= 2.7V

V

BATT

= 2V, SELI = GND or IN

SELV = GND, I

BATT

= 0

SELV = IN, I

BATT

= 0

BATT Leakage Current (Input

Power Removed)

BATT Shutdown Current

Logic Input Low Voltage (EN, SELI, SELV)

Logic Input High Voltage (EN, SELI, SELV)

Logic Input Leakage Current (EN, SELI)

Logic Input Leakage Current (SELV)

Thermal Regulation

V

BATT

= 4.2V, EN = IN = GND

EN = GND, V

BATT

= 4.2V

V

IN

= 4.35V to 6.5V

V

IN

= 4.35V to 6.5V

V

IN

= 0 to 6.5V; V

SELI

, V

EN

= 6.5V or GND

V

IN

= 0 to 6.5V, V

SELV

= V

IN

or GND

Die temperature beyond which charging current is reduced

MIN

4.35

3.75

2.3

20

4.08

4.18

2.0

TYP

50

0.9

2.5

100

200

2.5

80

0.1

455

85

43

4.10

4.20

1

0.1

125

1.0

0.4

500

100

70

4.12

4.22

MAX UNITS

6.50

V

4.05

V mV

2.0

5.0

mA

µA

2.7

5

2

0.8

1

1 mV

V mV

µA

V mA

V

µA

µA

V

V

µA

µA

°C

2 _______________________________________________________________________________________

USB-Powered Li+ Charger

ELECTRICAL CHARACTERISTICS

(V

IN

= 4.5V, T

A

= -40°C to +85°C, unless otherwise noted.) (Note1)

PARAMETER

Input Supply Voltage

Input Undervoltage Lockout

CONDITIONS

Input Supply Current

Precondition Threshold

BATT Regulation Voltage

I

IN

rising

Operating, EN = IN, no load

Shutdown, EN = GND

BATT rising, transition from precondition to charge mode

SELV = GND, I

BATT

= 0

SELV = IN, I

BATT

= 0

BATT Leakage Current (Input

Power Removed)

V

BATT

= 4.2V, IN = GND

BATT Shutdown Current EN = GND, V

BATT

= 4.2V

Note 1: Specifications to -40

°C are guaranteed by design and not production tested.

MIN

4.35

3.75

2.3

4.06

4.16

TYP MAX UNITS

6.50

V

4.05

3

6

V mA

µA

V 2.7

4.14

4.24

V

10

3

µA

µA

Typical Operating Characteristics

(CHG unconnected, C

BATT

= 2.2µF, T

A

= +25°C, unless otherwise noted.)

SUPPLY CURRENT vs. INPUT VOLTAGE (ENABLED)

0.7

0.6

0.5

0.4

0.3

1.0

0.9

0.8

0.2

0.1

0

0

V

IN

= V

EN

= V

SELV

1

V

SELI

2

= V

IN

V

3

V

IN

(V)

4

SELI

= 0

5 6 7

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

0

SUPPLY CURRENT vs. INPUT VOLTAGE

(SHUTDOWN)

V

IN

= V

SELV

V

EN

= 0

1 2 3

V

IN

(V)

4 5 6 7

500

450

400

350

300

250

200

150

100

50

0

0

CHARGE CURRENT vs. INPUT VOLTAGE HEADROOM

0.5

V

SELI

= V

IN

V

SELI

= 0

1.0

1.5

V

IN

- V

BATT

(V)

2.0

V

BATT

= 4.1V

V

SELV

= V

IN

2.5

3.0

_______________________________________________________________________________________

3

USB-Powered Li+ Charger

Typical Operating Characteristics (continued)

(CHG unconnected, C

BATT

= 2.2µF, T

A

= +25°C, unless otherwise noted.)

CHARGE CURRENT vs. BATTERY CURRENT

CHARGE CURENT vs. INPUT VOLTAGE

500

450 V

IN

= V

EN

= V

SELV

= 5.5V

500

450

V

BATT

= 4.1V

V

SELV

= V

IN

400

350

V

SELI

= V

IN

400

350

300

250

200

150

V

SELI

= 0

300

250

200

V

SELI

= V

IN

V

SELI

= 0

150

100

50

100

50

0

-50

0

0 0.5

1.0 1.5

2.0 2.5 3.0 3.5 4.0

4.5

V

BATT

(V)

0 1 2 3

V

IN

(V)

4 5 6 7

4.22

4.20

4.18

4.16

4.14

4.12

4.10

4.08

-40

BATTERY REGULATION VOLTAGE vs. TEMPERATURE

V

SELV

= V

IN

V

IN

= V

SELI

= V

EN

= 4.5V

I

BATT

= 0

-15

V

SELV

= 0

10 35

TEMPERATURE (

°C)

60 85

600

CHARGE CURRENT vs. TEMPERATURE

V

IN

= V

SELV

= V

EN

= 5.5V, V

BATT

= 2.7V

500

400

V

SELI

= V

IN

300

200

100

0

-40

V

SELI

= 0

-15 10 35

TEMPERATURE (

°C)

60 85

600

CHARGE CURRENT vs. TEMPERATURE

WITH THERMAL REGULATION

V

IN

= V

SELV

= V

EN

= 6.5V, V

BATT

= 2.7V

500

V

SELI

= V

IN

400

300

200

V

SELI

= 0

THERMAL CONTROL

LOOP IN OPERATION

100

0

-40 -15 10 35

TEMPERATURE (

°C)

60 85

4 _______________________________________________________________________________________

USB-Powered Li+ Charger

PIN

1

2

3, 6

4

5

7

8

SELI

GND

IN

BATT

EN

CHG

NAME

SELV

Pin Description

DESCRIPTION

Battery Regulation Voltage-Select Input. A low (< 0.8V) selects a 4.1V battery regulation set point. A high

(> 2.0V) selects a 4.2V battery regulation set point.

Battery Regulation Current-Select Input. A low (< 0.8V) selects a 100mA maximum battery regulation current. A high (> 2.0V) selects a 500mA maximum battery regulation current. SELI is not diode clamped to IN, and the voltage at V

SELI

can exceed the voltage at V

IN

.

Ground. Connect pins 3 and 6 to a large copper trace for maximum power dissipation.

Input Supply Voltage. Bypass with a 4.7µF capacitor to GND.

Li+ Battery Connection. Bypass with a capacitor no less than 2.2µF to GND. High impedance in shutdown.

Enable Input. A high (> 2.0V) enables the device. A low (< 0.8V) disables the device and places it into shutdown mode. BATT is high impedance when disabled.

Charging Indicator Open-Drain Output.

CHG pulls low while the device is in charge mode (2.5V

< V

BATT

< BATT Regulation Voltage).

SELI

IN

VOLTAGE

LOOP

CURRENT

SELECTOR

REGULATOR

BATT

THERMAL

LOOP

3V

CHG

EN BIAS

VOLTAGE

SELECTOR

2V

OVERCURRENT

DETECTOR

(2.5V, 4.2V)

4.7V

BATTERY

OVERVOLTAGE

DETECTOR

MAX

DETECTOR

CIRCUIT

CURRENT

LOOP

MAX1811

CURRENT-

SENSE

CIRCUIT

SELV

GND

Figure 1. Functional Diagram

_______________________________________________________________________________________ 5

USB-Powered Li+ Charger

Detailed Description

Charger-Control Circuitry

The voltage/current regulator consists of a voltage control loop, a current control loop, and a thermal control loop (Figure 1). Use the SELV input to set the battery regulation voltage to a 4.1V or 4.2V single Li+ cell. The current and thermal loops are internally compensated and require no external compensation. The outputs from all loops drive an internal linear regulator. The thermal loop modulates the current loop by limiting the charge current if the die temperature exceeds +125°C.

The MAX1811 is in current mode when the BATT voltage is below the regulation set point and in voltage mode when the BATT voltage is near the regulation set point. The CHG output indicates whether the part is in current mode (CHG = low) or voltage mode (CHG = high impedance). Battery voltages less than 2.5V activate a 43mA preconditioning mode (CHG = high impedance). Normal charging resumes when the battery voltage exceeds 2.5V.

System Configuration

The MAX1811 is designed to operate seamlessly with a universal serial bus (USB) port. In a typical design, the

USB connects to the MAX1811 input, and the MAX1811 drives the load and charges the battery when enabled.

Charge-Current Selection

The MAX1811 charges a single cell Li+ battery in either

100mA or 500mA modes. The MAX1811 expects the system to poll the USB host to determine if the USB is capable of providing 100mA or 500mA and regulates the charging current accordingly (Figure 2). This is to maintain compatibility with both powered and unpowered USB hosts. A powered USB host is capable of providing 500mA, and an unpowered USB hub is limited to only 100mA.

Drive SELI low to set the charge current to the 100mA mode. Use a 10k

Ω pulldown resistor to ground on SELI, if necessary, to ensure that the MAX1811 defaults to the 100mA mode in the event that no logic signal is present. Drive SELI high to increase the charge current to the 500mA mode only if the polled USB port can provide the required current.

Thermal-Control Circuitry

The thermal loop limits the MAX1811 die temperature to

+125°C by reducing the charging current as necessary. The MAX1811 can operate normally with the thermal loop active. This is not a fault condition and can be used continuously. The power dissipated by the internal power FET is determined by (V

IN

- V

BATT

)

I

CHG

.

The power dissipation rating for the thermally enhanced

8-pin SO package is 1.4W at +50°C ambient (assuming a 1in

2

PC board radiating area), which is the maximum ambient temperature at which most Li+ battery manufacturers allow charging. The 1.4W power dissipation may never be reached due to the MAX1811’s thermal regulation loop.

Applications Information

USB Output Voltage

The minimum voltage to a USB-powered device may be as low as 4.35V when cable and connector drops are considered (Figure 3). The MAX1811 is optimized for operation at these low input voltage levels. USB hubs may also provide as much as 5.5V. At high input voltages (5.5V) and low cell voltages (2.7V), the

MAX1811’s thermal loop may limit the charge current until the cell voltage rises.

USB*

PORT

4.35V TO 5.5V

IN

MAX1811

BATT

SINGLE

Li+

CELL

SYSTEM

LOAD

*WHEN USING WALL ADAPTER, IN VOLTAGE RANGE IS FROM 4.35V TO 6.5V.

Figure 2. System Configuration

6 _______________________________________________________________________________________

USB-Powered Li+ Charger

Charging from AC Adapters

The MAX1811 also operates from sources other than

USB ports. The full charging input voltage range is

4.35V to 6.5V. When charging in the 500mA mode with an AC adapter, rely on the thermal loop to limit the power dissipation by limiting the charge current at higher input voltages if limited PC board area is available to dissipate heat.

Capacitor Selection

Use a minimum of 2.2µF placed close to BATT for proper stability. Bypass IN to GND with a 4.7µF capacitor.

Use a larger input bypass capacitor for high input voltages or high charging current to reduce supply noise.

TRANSISTOR COUNT: 1907

PROCESS: BiCMOS

Chip Information

HOST OR

POWERED HUB

4.750V

4.735V

4.640V

BUS-POWERED

HUB

4.625V

*4.400V

4.500V

4.397V

0.000V

0.015V

0.110V

0.125V

0.000V

REFERENCED

TO SOURCE

REFERENCED

TO HUB

*UNDER TRANSIENT CONDITIONS, SUPPLY AT HUB CAN DROP FROM 4.00V TO 4.070V.

0.003V

Figure 3. USB Voltage Specification

4.378V

4.375V

LOW-POWER

FUNCTION

4.350V

0.002V

0.025V

4.35V TO 6.5V

4.2V

4.1V

ON

OFF

500mA

100mA

10k

IN

SELV

EN

SELI

MAX1811

BATT

CHG

GND

GND

LED

TO LOAD

SINGLE

Li+

CELL

TO IN

CHG

LOGIC OUT

Figure 4. Charging from a USB Port

_______________________________________________________________________________________ 7

USB-Powered Li+ Charger

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to

www.maxim-ic.com/packages

.)

N

1

TOP VIEW

E H

B

C e

E

H

L

DIM

A

A1

INCHES

MIN

0.053

0.004

0.014

0.007

MAX

0.069

0.010

0.019

0.010

0.050 BSC

0.150

0.228

0.016

0.157

0.244

0.050

MILLIMETERS

MIN

1.35

MAX

1.75

0.25

0.10

0.35

0.19

0.49

0.25

1.27 BSC

3.80

5.80

4.00

6.20

0.40

1.27

VARIATIONS:

DIM

D

D

D

INCHES

MIN

0.189

0.337

0.386

MAX

0.197

0.344

0.394

MILLIMETERS

MIN

4.80

8.55

9.80

MAX

5.00

8.75

10.00

N MS012

8 AA

14

16

AB

AC

D e

FRONT VIEW

B

A1

A

C

L

SIDE VIEW

0 -8

PROPRIETARY INFORMATION

TITLE:

PACKAGE OUTLINE, .150" SOIC

APPROVAL DOCUMENT CONTROL NO.

21-0041

REV.

B

1

1

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

This datasheet has been download from: www.datasheetcatalog.com

Datasheets for electronics components.

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