Datasheet

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LTC4068-4.2/LTC4068X-4.2

406842fa

Standalone Linear

Li-Ion Battery Charger with

Programmable Termination

■

Programmable Charge Current Up to 950mA

■

Complete Linear Charger in DFN Package

■

No MOSFET, Sense Resistor or Blocking Diode

Required

■

Thermal Regulation Maximizes Charge Rate

Without Risk of Overheating*

■

Charges Directly from a USB Port

■

Programmable Charge Current Termination

■

Preset 4.2V Charge Voltage with ±1% Accuracy

■

Charge Current Monitor Output for Gas Gauging*

■

Automatic Recharge

■

Charge Status Output

■

“AC Present” Output

■

2.9V Trickle Charge Threshold (LTC4068)

■

Available Without Trickle Charge (LTC4068X)

■

Soft-Start Limits Inrush Current

■

Low Profile (3mm × 3mm × 0.75mm) DFN Package

■

Cellular Telephones, PDAs, MP3 Players

■

Bluetooth Applications

, LTC and LT are registered trademarks of Linear Technology Corporation.

The LTC

4068 is a complete constant-current/constant-

voltage linear charger for single cell lithium-ion batteries.

Its DFN package and low external component count make

the LTC4068 ideally suited for portable applications. Fur-

thermore, the LTC4068 is designed to work within USB

power specifications.

No external sense resistor or external blocking diode are

required due to the internal MOSFET architecture. Thermal

feedback regulates the charge current to limit the die

temperature during high power operation or high ambient

temperature conditions. The charge voltage is fixed at

4.2V and the charge current is programmed with a resis-

tor. The LTC4068 terminates the charge cycle when the

charge current drops below the programmed termination

threshold after the final float voltage is reached.

When the input supply (wall adapter or USB supply) is

removed, the LTC4068 enters a low current state dropping

the battery drain current to less than 2µA. Other features

include charge current monitor, undervoltage lockout,

automatic recharge and status pins to indicate charge

termination and the presence of adequate input voltage.

BATV

CHRG

1.65k

406842 TA01

1µF

4.5V TO 6.5V

1-CELL

Li-Ion

BATTERY

LTC4068-4.2

600mA

ACPR

EN PROG

GND

ITERM

825Ω

TIME (HOURS)

CHARGE CURRENT (mA)

1.5

406842 TA02

0.5 1.0 2.25

700

600

500

400

300

200

100

4.75

4.50

4.25

4.00

3.75

3.50

3.25

3.00

0.25 0.75 1.25 2.01.75

CONSTANT

VOLTAGE

CONSTANT

CURRENT

BATTERY VOLTAGE (V)

= 5V

= 40°C/W

PROG

= 1.65k

TERM

= 825Ω

= 25°C

Complete Charge Cycle (750mAh Battery)

Protected by U.S. Patents, including 6522118.

Single Cell Li-Ion Battery Charger with C/5 Termination

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (12 pages)

PAGE 1
LTC4068-4.2/LTC4068X-4.2 Standalone Linear Li-Ion Battery Charger with Programmable Termination U FEATURES DESCRIPTIO ■ The LTC®4068 is a complete constant-current/constantvoltage linear charger for single cell lithium-ion batteries. Its DFN package and low external component count make the LTC4068 ideally suited for portable applications. Furthermore, the LTC4068 is designed to work within USB power specifications.
PAGE 2
LTC4068-4.2/LTC4068X-4.2 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage (VCC) ....................... –0.3V to 10V PROG, ITERM ................................ – 0.3V to VCC + 0.3V BAT ............................................................. –0.3V to 7V CHRG, ACPR, EN ...................................... –0.3V to 10V BAT Short-Circuit Duration .......................... Continuous BAT Pin Current ...................................................
PAGE 3
LTC4068-4.2/LTC4068X-4.2 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted.
PAGE 4
LTC4068-4.2/LTC4068X-4.2 U W TYPICAL PERFOR A CE CHARACTERISTICS Regulated Output (Float) Voltage vs Charge Current Regulated Output (Float) Voltage vs Temperature 4.26 4.215 4.215 VCC = 5V RPROG = 10k 4.210 4.16 4.205 VFLOAT (V) 4.18 TA = 25°C RPROG = 10k 4.210 4.205 4.20 VFLOAT (V) VFLOAT (V) VCC = 5V 4.24 TA = 25°C RPROG = 1.25k 4.22 Regulated Output (Float) Voltage vs Supply Voltage 4.200 4.200 4.195 4.195 4.190 4.190 4.14 4.12 4.10 0 100 200 300 400 IBAT (mA) 500 600 4.
PAGE 5
LTC4068-4.2/LTC4068X-4.2 U W TYPICAL PERFOR A CE CHARACTERISTICS Charge Current vs Ambient Temperature Charge Current vs Supply Voltage 600 600 ONSET OF THERMAL REGULATION RPROG = 2k 500 500 RPROG = 2k 400 IBAT (mA) IBAT (mA) 400 VBAT = 4V 300 TA = 25°C θJA = 40°C/W 200 200 RPROG = 10k 100 0 VCC = 5V VBAT = 4V θJA = 40°C/W 300 4 5 4.5 5.5 VCC (V) RPROG = 10k 100 6 6.
PAGE 6
LTC4068-4.2/LTC4068X-4.2 U U U PI FU CTIO S PROG (Pin 5): Charge Current Program and Charge Current Monitor. Charge current is programmed by connecting a 1% resistor, RPROG, to ground. When charging in constant-current mode, this pin servos to 1V. In all modes, the voltage on this pin can be used to measure the charge current using the following formula: When VCC is within 100mV of the BAT pin voltage, the LTC4068 enters shutdown mode dropping the battery drain current to less than 2µA.
PAGE 7
LTC4068-4.2/LTC4068X-4.2 U OPERATIO The LTC4068 is a single cell lithium-ion battery charger using a constant-current/constant-voltage algorithm. It can deliver up to 950mA of charge current (using a good thermal PCB layout) with a final float voltage accuracy of ±1%. The LTC4068 includes an internal P-channel power MOSFET and thermal regulation circuitry. No blocking diode or external current sense resistor is required; thus, the basic charger circuit requires only two external components.
PAGE 8
LTC4068-4.2/LTC4068X-4.2 U OPERATIO threshold (VRECHRG), another charge cycle begins and charge current is once again supplied to the battery. To manually restart a charge cycle when in standby mode, the input voltage must be removed and reapplied or the charger must be shut down and restarted using the EN pin. Figure 1 shows the state diagram of a typical charge cycle. POWER ON BAT < 2.
PAGE 9
LTC4068-4.2/LTC4068X-4.2 U W U U APPLICATIO S I FOR ATIO charged condition and eliminates the need for periodic charge cycle initiations. The CHRG output enters a pulldown state during recharge cycles. If the battery is removed from the charger, a sawtooth waveform of approximately 100mV appears at the charger output. This is caused by the repeated cycling between termination and recharge events.
PAGE 10
LTC4068-4.2/LTC4068X-4.2 U W U U APPLICATIO S I FOR ATIO The LTC4068 can be used above 52°C ambient but the charge current will be reduced from the programmed 800mA. The approximate current at a given ambient temperature can be approximated by: IBAT = 120°C – TA (VCC – VBAT ) • θJA Using the previous example with an ambient temperature of 60°C, the charge current will be reduced to approximately: IBAT = 120°C – 60°C (5V – 3.
PAGE 11
LTC4068-4.2/LTC4068X-4.2 U W U U APPLICATIO S I FOR ATIO Reverse Polarity Input Voltage Protection DRAIN-BULK DIODE OF FET In some applications, protection from reverse polarity voltage on VCC is desired. If the supply voltage is high enough, a series blocking diode can be used. In other cases, where the voltage drop must be kept low, a P-channel MOSFET can be used (as shown in Figure 4). LTC4068 VCC VIN 405842 F04 Figure 4.
PAGE 12
LTC4068-4.2/LTC4068X-4.2 U TYPICAL APPLICATIO S Full Featured Single Cell Li-Ion Charger Li-Ion Battery Charger with Reverse Polarity Input Protection VIN 5V 1k 1k 5V WALL ADAPTER 6 500mA VCC 1µF 6 VCC 2 7 ACPR BAT 1 3 CHRG ITERM LTC4068-4.2 8 5 EN PROG GND BAT LTC4068-4.