Maxim MAX1679EUA Datasheet

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General Description

The MAX1679 battery charger for a single lithium-ion (Li+)
cell comes in a space-saving 8-pin µMAX package. This
simple device, in conjunction with a current-limited wall
cube and a PMOS transistor, allows safe and fast charg­ing of a single Li+ cell.

The MAX1679 initiates charging in one of three ways:
battery insertion, charger power-up, or external manip­ulation of the THERM pin. Charging terminates when
the average charging current falls to approximately 1%
of the fast-charge current, or when the on-chip counter
times out.

Key safety features include continuous voltage and
temperature monitoring, a programmable charger time­out, and a 5mA precharge current mode to charge
near-dead cells. Automatic detection of input power
removal shuts down the device, minimizing current
drain from the battery. An overall system accuracy of

0.75% ensures that the cell capacity is fully utilized
without cycle life degradation.

The MAX1679 evaluation kit (MAX1679EVKIT) is avail­able to help reduce design time.

Applications

Single-Cell Li+ Portable Applications
Self-Charging Battery Packs
PDAs
Cell Phones
Cradle Chargers

Features

♦ Simple Stand-Alone Application Circuit
♦ Lowest Power Dissipation
♦ 8-Pin µMAX Package Saves Space
♦ No Inductor Required
♦ 0.75% Overall System Accuracy
♦ Continuous Voltage and Temperature Protection
♦ Safely Precharges Near-Dead Cells
♦ Programmable Safety Timeout
♦ Top-Off Charging to Achieve Full Battery Capacity
♦ Automatic Power-Down when Power Source is

Removed

MAX1679

Single-Cell Li+ Battery Charger

for Current-Limited Supply

________________________________________________________________

Maxim Integrated Products

1

Typical Operating Circuit

19-1545; Rev 0; 9/99

EVALUATION KIT

AVAILABLE

Pin Configuration

Ordering Information

PIN-PACKAGETEMP. RANGEPART

8 µMAX-40°C to +85°CMAX1679EUA

TOP VIEW

GATE

CHG

1

IN

2

MAX1679

3

4

µMAX

8

7

6

5

BATT

THERM

GND

ADJTSEL

CURRENT-

LIMITED

VOLTAGE

SOURCE

LED

TIMER

RANGE

SELECT

THERMISTOR

IN

CHG

TSEL

THERM ADJ

PFET

GATE

BATT

BATTERY

MAX1679

GND

%

MAX1679

Single-Cell Li+ Battery Charger
for Current-Limited Supply

2 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(VIN= V

CHG

= +10V, V

BATT

= +4.2V, TSEL = GND, GATE = unconnected, ADJ = unconnected, THERM = 10kΩ to GND, TA= 0°C

to +85°C, unless otherwise noted. Typical values are at T

A

= +25°C.)

IN, CHG, GATE to GND ........................................ -0.3V to +26V

BATT, TSEL, THERM, ADJ to GND ........................ -0.3V to +6V

GATE to IN................................................................-6V to +0.3V

THERM, ADJ to BATT...............................................-6V to +0.3V

GATE Continuous Current ................................................ -10mA

Continuous Power Dissipation (T

A

= +70°C)

8-Pin µMAX (derate 4.1mW/°C above +70°C) ........... 330mW

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

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

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

PARAMETER SYMBOL MIN TYP MAX UNITSCONDITIONS

CHG Output Leakage Current

-1 +1 µA

V

CHG

= 22V, CHG = high

Timer Accuracy -10 +10 %See Table 3

IN Input Current, Done State I

IN

250 600 µAV

BATT

= 4.25V, VIN= 22V

IN Input Current, Fast-Charge
State

I

IN

30 100 µAV

BATT

= 4V, VIN= 4V

BATT Input Current, Done State I

BATT

500 1000 µAV

BATT

= 4.25V

BATT Input Current, Fast­Charge State

I

BATT

900 1500 µAV

BATT

= 4V

BATT Input Current (Note 2) 0.1 1 µAVIN≤ V

BATT

-0.3V

Battery Removal Detection
Threshold

4.875 5.0 5.125 VV

BATT

rising

Battery Removal Detection
Threshold Hysteresis

125 mVV

BATT

falling

BATT Regulation Adjust Range 4.0 4.2 V

Precharge Source Current 456mA

Fast-Charge Restart Threshold 3.783 3.89 4.00 V

Fast-Charge Qualification
Threshold

2.425 2.500 2.575 V

Undervoltage Lockout Trip-Point
Hysteresis

60 mV

BATT Regulation Voltage 4.1685 4.2000 4.2315 V

Input Voltage for Removable
Battery (Note 1)

Input Voltage (Note 1) V

IN

522V

V

IN

622V

Undervoltage Lockout Trip Point 2.1 2.2 2.3 V

V

BATT

= 2V

V

BATT

falling, transition from DONE to

PREQUAL state (Figure 2)

V

BATT

rising, transition from precharge to full

current

V

BATT

falling

External PMOS FET off

External PMOS FET off

V

BATT

rising

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.

ADJ Source Impedance 9.8 10 10.2 kΩ
ADJ Output Voltage 1.393 1.400 1.407 VNo load on ADJ

%

Single-Cell Li+ Battery Charger

for Current-Limited Supply

MAX1679

_______________________________________________________________________________________ 3

PARAMETER SYMBOL MIN TYP MAX UNITSCONDITIONS

GATE Drive Current at Battery
Removal

20 40 60 mAV

BATT

= 5.1V, gate driven high

GATE Source/Sink Current 75 105 130 µAVIN= 10V, V

GATE

= 8V

THERM Sense Voltage Trip
Point

1.379 1.40 1.421 V

THERM Sense Current (for cold
qualification)

47.8 48.8 49.8 µA

THERM Sense Current (for hot
qualification)

346 352.9 360 µA

CHG Output Sink Current

456mA

V

CHG

= 1V, CHG = low

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

CHG

= +10V, V

BATT

= +4.2V, TSEL = GND, GATE = unconnected, ADJ = unconnected, THERM = 10kΩ to GND, TA= 0°C

to +85°C, unless otherwise noted. Typical values are at T

A

= +25°C.)

ELECTRICAL CHARACTERISTICS

(VIN= V

CHG

= +10V, V

BATT

= +4.2V, TSEL = GND, GATE = unconnected, ADJ = unconnected, THERM = 10kΩ to GND, TA= -40°C

to +85°C, unless otherwise noted.)

BATT Regulation Adjust Range 4.0 4.2 V

Undervoltage Lockout Trip Point 2.05 2.35 VV

BATT

rising

PARAMETER SYMBOL MIN MAX UNITS

Precharge Source Current 37mA

Fast-Charge Restart Threshold 3.74 4.04 V

Fast-Charge Qualification
Threshold

2.35 2.65 V

BATT Regulation Voltage 4.137 4.263 V

Input Voltage for Removable
Battery (Note 1)

Input Voltage (Note 1) V

IN

522V

V

IN

622V

CONDITIONS

V

BATT

= 2V

V

BATT

falling, transition from DONE to

PREQUAL state, Figure 2

V

BATT

rising, transition from precharge to full

current

ADJ Source Impedance 9.8 10.2 kΩ

External PMOS FET off

External PMOS FET off

ADJ Output Voltage 1.386 1.414 VNo load on ADJ
Battery Removal Detection

Threshold

4.850 5.150 VV

BATT

rising

BATT Input Current (Note 2) 1 µAVIN≤ V

BATT

- 0.3V

BATT Input Current, Fast­Charge State

I

BATT

1500 µAV

BATT

= 4.0V

BATT Input Current, Done State I

BATT

1000 µAV

BATT

= 4.25V

IN Input Current, Fast-Charge
State

I

IN

100 µAV

BATT

= 4.0V, VIN= 4.0V

MAX1679

Single-Cell Li+ Battery Charger
for Current-Limited Supply

4 _______________________________________________________________________________________

THERM Sense Voltage Trip
Point

1.358 1.442 V

GATE Drive Current at Battery
Removal

20 90 mAV

BATT

= 5.1V, gate driven high

GATE Source/Sink Current 60 140 µAVIN= 10V, V

GATE

= 8V

PARAMETER SYMBOL MIN MAX UNITS

THERM Sense Current (for cold
qualification)

47.3 50.3 µA

THERM Sense Current (for hot
qualification)

342 363 µA

CHG Output Sink Current

46mA

V

CHG

= 1.0V, CHG = low

CHG Output Leakage Current

-1 +1 µA

V

CHG

= 22V, CHG = high

Timer Accuracy -15 +15 %See Table 3

IN Input Current, Done State I

IN

700 µAV

BATT

= 4.25V, VIN= 22V

CONDITIONS

ELECTRICAL CHARACTERISTICS (continued)

(VIN= V

CHG

= +10V, V

BATT

= +4.2V, TSEL = GND, GATE = unconnected, ADJ = unconnected, THERM = 10kΩ to GND, TA= -40°C

to +85°C, unless otherwise noted.)

Note 1: The input voltage range is specified with the external PFET off. When charging, the PFET turns on and the input voltage

(the output voltage of the constant-current power source) drops to very near the battery voltage. When the PFET is on, V

IN

may be as low as 2.5V.

Note 2: BATT Input Current is the supply current to the device. When VINis removed, the MAX1679 shuts down and the input current

is less than 1µA, even if there is an external R

ADJ

resistor (ADJ to GND).