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LTC4002

4002f

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

All other trademarks are the property of their respective owners.

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

■

Portable Computers

■

Charging Docks

■

Handheld Instruments

■

Wide Input Supply Range:

4.7V to 22V – 4.2 Version

8.9V to 22V – 8.4 Version

■

High Efficiency Current Mode PWM Controller with

500kHz Switching Frequency

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±1% Charge Voltage Accuracy

■

End-of-Charge Current Detection Output

■

3 Hour Charge Termination Timer

■

Constant Switching Frequency for Minimum Noise

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±5% Charge Current Accuracy

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Low 10µA Reverse Battery Drain Current

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Automatic Battery Recharge

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Automatic Shutdown When Input Supply is Removed

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Automatic Trickle Charging of Low Voltage Batteries

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Battery Temperature Sensing and Charge

Qualification

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Stable with Ceramic Output Capacitor

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8-Lead SO and 10-Lead DFN Packages

Standalone Li-Ion

Switch Mode Battery Charger

The LTC

4002 is a complete battery charger controller for

one (4.2V) or two (8.4V) cell lithium-ion batteries. With a

500kHz switching frequency, the LTC4002 provides a

small, simple and efficient solution to fast charge Li-Ion

batteries from a wide range of supply voltages. An external

sense resistor sets the charge current with ±5% accuracy.

An internal resistor divider and precision reference set the

final float voltage to 4.2V per cell with ±1% accuracy.

When the input supply is removed, the LTC4002 automati-

cally enters a low current sleep mode, dropping the battery

drain current to 10µA. An internal comparator detects the

near end-of-charge condition while an internal timer sets

the total charge time and terminates the charge cycle. After

the charge cycle ends, if the battery voltage drops below

4.05V per cell, a new charge cycle will automatically begin.

The LTC4002 is available in the 8-lead SO and 10-lead DFN

packages.

6.8µH

22µF

4002 TA01

NTC: DALE NTHS-1206N02

10µF

0.1µF

0.47µF

2.2k

68mΩ

Li-Ion

BATTERY

10k

NTC

SENSE

GATE

BAT

CHRG

LTC4002ES8-4.2

5V TO 22V

BAT

NTC GND

COMP

CHARGE

STATUS

1.5A Single Cell Li-Ion Battery Charger

INPUT VOLTAGE (V)

EFFICIENCY (%)

BAT

= 4V

4002 TA02

100

BAT

= 3.8V

(CURVES INCLUDE

INPUT DIODE)

Efficiency vs Input Voltage

Summary of content (16 pages)

PAGE 1
LTC4002 Standalone Li-Ion Switch Mode Battery Charger U FEATURES DESCRIPTIO ■ The LTC®4002 is a complete battery charger controller for one (4.2V) or two (8.4V) cell lithium-ion batteries. With a 500kHz switching frequency, the LTC4002 provides a small, simple and efficient solution to fast charge Li-Ion batteries from a wide range of supply voltages. An external sense resistor sets the charge current with ±5% accuracy.
PAGE 2
LTC4002 W W U W ABSOLUTE AXI U RATI GS (Note 1) Supply Voltage (VCC) .............................................. 24V GATE .................................................. (VCC – 8V) to VCC BAT, SENSE .............................................. – 0.3V to 14V CHRG, NTC ................................................. – 0.3V to 8V Operating Temperature Range (Note 4) .. – 40°C to 85°C Storage Temperature Range ................. – 65°C to 125°C Lead Temperature (S8 Package) (Soldering, 10 sec) .
PAGE 3
LTC4002 ELECTRICAL CHARACTERISTICS (LTC4002-4.2) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 10V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX INTC NTC Pin Output Current VNTC = 0.85V ● 75 85 95 µA VNTC-HOT NTC Pin Threshold Voltage (Hot) VNTC Falling Hysteresis ● 340 355 25 370 mV mV VNTC-COLD NTC Pin Threshold Voltage (Cold) VNTC Rising Hysteresis ● 2.428 2.465 170 2.
PAGE 4
LTC4002 ELECTRICAL CHARACTERISTICS (LTC4002-8.4) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VNTC-HOT NTC Pin Threshold Voltage (Hot) VNTC Falling Hysteresis ● 340 355 25 370 mV mV VNTC-COLD NTC Pin Threshold Voltage (Cold) VNTC Rising Hysteresis ● 2.428 2.465 170 2.
PAGE 5
LTC4002 U W TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C, VCC = 10V unless otherwise noted. Undervoltage Lockout Threshold vs Temperature Oscillator Frequency vs VCC 510 8 CHRG Pin Output Low Voltage vs VCC 150 VCC RISING ILOAD = 1mA LTC4002-8.4 500 VCHRG (mV) VUV (V) fOSC (kHz) 7 6 140 5 LTC4002-4.
PAGE 6
LTC4002 U W TYPICAL PERFOR A CE CHARACTERISTICS Current Mode Sense Voltage vs VCC Current Mode Sense Voltage vs Temperature 102 100 50 75 25 TEMPERATURE (°C) 100 102 VBAT = 4V LTC4002-4.2 100 98 0 125 5 15 10 20 100 15 20 86 100 96 – 50 – 25 25 50 75 25 TEMPERATURE (°C) 100 125 20 5.2 LTC4002-4.2 2.9 5 10 15 25 Trickle Charge Voltage vs Temperature 20 25 VCC (V) 4002 G19 15 10 4002 G18 VTRKL (V) VTRKL (V) VTRKL (V) 3.0 2.
PAGE 7
LTC4002 U W TYPICAL PERFOR A CE CHARACTERISTICS Trickle Charge Sense Voltage vs Temperature Trickle Charge Voltage vs VCC 10.4 5.0 4.8 5 15 10 20 11 VBAT = 2.5V LTC4002-4.2 10.0 9.6 – 50 – 25 25 0 50 75 25 TEMPERATURE (°C) VCC (V) 100 100 125 89 VBAT = 4V LTC4002-8.4 10 9 5 10 15 20 85 0 50 75 25 TEMPERATURE (°C) VCC (V) 100 125 4002 G27 4002 G26 End-of-Charge Ratio vs Temperature End-of-Charge Ratio vs VCC 28 REOC (%) LTC4002-4.
PAGE 8
LTC4002 U W TYPICAL PERFOR A CE CHARACTERISTICS End-of-Charge Ratio vs Temperature End-of-Charge Ratio vs VCC 14 LTC4002-8.4 13 13 12 12 11 11 REOC (%) REOC (%) 14 10 9 8 8 7 7 6 0 50 75 25 TEMPERATURE (°C) 100 125 4002 G30 U U U PI FU CTIO S LTC4002-8.4 10 9 6 – 50 – 25 TA = 25°C, VCC = 10V unless otherwise noted. 5 10 15 VCC (V) 20 25 4002 G31 (DFN/SO-8) COMP (Pin 1/Pin 1): Compensation, Soft-Start and Shutdown Control Pin.
PAGE 9
LTC4002 U U U PI FU CTIO S (DFN/SO-8) hot temperature or rises above 2.465V at cold temperature, charging is suspended and the internal timer stops. The CHRG pin output is not affected during this hold state. To disable the temperature qualification function, ground the NTC pin. NC (Pin 10/NA): No Connect. W BLOCK DIAGRA VCC CLK: 100µA COMP ISLOP IL DRIVER – GATE S Q + CPWM R RSLOP 25mV or 10mV R + +– CEOC – RIL 100mV + M1 SENSE –+ CA – BAT + M2 VA – 4.
PAGE 10
LTC4002 TEST CIRCUITS Test Circuit 1 15V – 1.5V LT1006 LT1006 + + 0V 0V SENSE LTC4002 – 100µA SENSE CA BAT RSENSE 10Ω + 1mA COMP 100µA CA BAT RSENSE 10Ω + COMP 15V – – 1.5V Test Circuit 2 VBAT – 4002 TC01 VA 4.2V + LTC4002 4002 TC02 U OPERATIO The LTC4002 is a constant current, constant voltage Li-Ion battery charger controller that uses a current mode PWM step-down (buck) switching architecture.
PAGE 11
LTC4002 U OPERATIO mode, dropping ICC to 10µA. This will greatly reduce the current drain on the battery and increase the standby time. A 10kΩ NTC (negative temperature coefficient) thermistor can be connected from the NTC pin to ground for battery temperature qualification. The charge cycle is suspended when the temperature is outside of the 0°C to 50°C window (with DALE NTHS-1206N02).
PAGE 12
LTC4002 U W U U APPLICATIO S I FOR ATIO impedance state, the current source will pull the pin low through the 390k resistor. When the internal timer has expired, the CHRG pin changes to a high impedance state and the 390k resistor will then pull the pin high to indicate charging has stopped. Gate Drive The LTC4002 gate driver can provide high transient currents to drive the external pass transistor.
PAGE 13
LTC4002 U W U U APPLICATIO S I FOR ATIO Input and Output Capacitors Since the input capacitor is assumed to absorb all input switching ripple current in the converter, it must have an adequate ripple current rating. Worst-case RMS ripple current is approximately one-half of output charge current. Actual capacitance value is not critical.
PAGE 14
LTC4002 U W U U APPLICATIO S I FOR ATIO Board Layout Suggestions Next, choose the P-channel MOSFET. The Si6435ADQ in a TSSOP-8 package with RDS(ON) = 42mΩ (nom), 55mΩ (max) offers a small solution. The maximum power dissipation with VIN = 5V and VBAT = 4V at 50°C ambient temperature is: When laying out the printed circuit board, the following considerations should be taken to ensure proper operation of the LTC4002. GATE pin rise and fall times are 20ns and 50ns respectively (with CGATE = 2000pF).
PAGE 15
LTC4002 U PACKAGE DESCRIPTIO DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699) R = 0.115 TYP 6 0.38 ± 0.10 10 0.675 ±0.05 3.50 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) 3.00 ±0.10 (4 SIDES) PACKAGE OUTLINE 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) (DD10) DFN 1103 5 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 0.200 REF 0.25 ± 0.05 1 0.50 BSC 2.38 ±0.05 (2 SIDES) 2.38 ±0.10 (2 SIDES) 0.00 – 0.
PAGE 16
LTC4002 U TYPICAL APPLICATIO 2-Cell 8.4V, 2A Li-Ion Battery Charger VIN 9V TO 12V R1 100k M2 1/2 Si9933ADY 2 C3 0.1µF CER VCC GATE 3 LTC4002ES8-8.4 5 1 CC 0.47µF CHRG SENSE BAT COMP NTC GND 8 4 RC 2.2k T 10k NTC M1 1/2 Si9933ADY C1 10µF CER D2 B330 L1 6.8µH 7 6 RSENSE 50mΩ C2 22µF CER + 8.4V Li-Ion BATTERY 4002 TA03 NTC: DALE NTHS-1206N02 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1732-8.4 2-Cell Li-Ion Linear Battery Charger 8.