Datasheet

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LTC4006

4006fa

TYPICAL APPLICATIO

APPLICATIO S

FEATURES

DESCRIPTIO

4A, High Efficiency,

Standalone Li-Ion

Battery Charger

■

Complete Charger Controller for 2-, 3- or 4-Cell

Lithium-Ion Batteries

■

High Conversion Efficiency: Up to 96%

■

Output Currents Exceeding 4A

■

±0.8% Accurate Preset Voltages: 8.4V, 12.6V, 16.8V

■

Built-In Charge Termination with Automatic Restart

■

AC Adapter Current Limiting Maximizes Charge Rate*

■

Automatic Conditioning of Deeply Discharged

Batteries

■

Thermistor Input for Temperature Qualified Charging

■

Wide Input Voltage Range: 6V to 28V

■

0.5V Dropout Voltage; Maximum Duty Cycle: 98%

■

Programmable Charge Current: ±4% Accuracy

■

Indicator Outputs for Charging, C/10 Current

Detection and AC Adapter Present

■

Charging Current Monitor Output

■

16-Pin Narrow SSOP Package

■

Notebook Computers

■

Portable Instruments

■

Battery-Backup Systems

■

Standalone Li-Ion Chargers

4A Li-Ion Battery Charger

The LTC

4006 is a complete constant-current/constant-

voltage charger controller for 2-, 3- or 4-cell lithium bat-

teries in a small package using few external components.

The PWM controller is a synchronous, quasi-constant fre-

quency, constant off-time architecture that will not gener-

ate audible noise even when using ceramic capacitors.

The LTC4006 is available in 8.4V, 12.6V and 16.8V versions

with ±0.8% voltage accuracy. Charging current is program-

mable with a single sense resistor to ±4% typical accuracy.

Charging current can be monitored as a representative

voltage at the I

MON

pin. A timer, programmed by an external

resistor, sets the total charge time or is reset to 25% of total

charge time after C/10 charging current is reached. Charg-

ing automatically resumes when the cell voltage falls below

3.9V/cell.

Fully discharged cells are automatically trickle charged at

10% of the programmed current until the cell voltage ex-

ceeds 2.5V/cell. Charging terminates if the low-battery

condition persists for more than 25% of the total charge

time.

The LTC4006 includes a thermistor sensor input that

suspends charging if an unsafe temperature condition is

detected and automatically resumes charging when the

battery temperature returns to within safe limits.

CHG

ACP

0.12µF

THERMISTOR

10k

NTC

309k

TIMING

RESISTOR

(~2 HOURS)

0.0047µF

0.47µF

32.4k

CHARGING

CURRENT MONITOR

100k

LOGIC

DCIN

0V TO 28V

INPUT SWITCH

0.1µF

15nF

20µF

10µH

0.025Ω

0.033Ω

20µF

BATTERY

TO SYSTEM LOAD

4006 TA01

DCIN

CHG

ACP/SHDN

MON

NTC

GND

INFET

CLP

CLN

TGATE

BGATE

PGND

CSP

BAT

LTC4006

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

All other trademarks are the property of their respective owners. Protected by U.S. Patents

including 5723970.

Summary of content (20 pages)

PAGE 1
LTC4006 4A, High Efficiency, Standalone Li-Ion Battery Charger DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Complete Charger Controller for 2-, 3- or 4-Cell Lithium-Ion Batteries High Conversion Efficiency: Up to 96% Output Currents Exceeding 4A ±0.8% Accurate Preset Voltages: 8.4V, 12.6V, 16.
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LTC4006 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Voltage from DCIN, CLP, CLN, TGATE, INFET, ACP/SHDN, CHG to GND ....................... + 32V to – 0.3V Voltage from CLP to CLN ..................................... ±0.3V CSP, BAT to GND ................................... +28V to – 0.3V RT to GND ................................................. +7V to – 0.3V NTC ........................................................ +10V to – 0.
PAGE 3
LTC4006 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range (Note 4), otherwise specifications are at TA = 25°C. VDCIN = 20V, VBAT = 12V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 140 165 200 mV Current Comparators ICMP and IREV ITMAX Maximum Current Sense Threshold (VCSP – VBAT) ITREV Reverse Current Threshold (VCSP – VBAT) VITH = 2.
PAGE 4
LTC4006 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range (Note 4), otherwise specifications are at TA = 25°C. VDCIN = 20V, VBAT = 12V unless otherwise noted.
PAGE 5
LTC4006 U W TYPICAL PERFOR A CE CHARACTERISTICS Disconnect/Reconnect Battery (Load Dump) Battery Leakage Current vs Battery Voltage 40 1A STEP VFLOAT 1V/(DIV) BATTERY LEAKAGE CURRENT (µA) 3A STEP 1A STEP 3A STEP LOAD STATE DISCONNECT RECONNECT VDCIN = 0V 35 30 25 20 15 10 5 0 LOAD CURRENT = 1A, 2A, 3A DCIN = 20V LTC4006-2 0 5 10 15 20 BATTERY VOLTAGE (V) 25 30 4006 G05 4006 G04 LTC4006-2 Efficiency with 15VDC VIN Efficiency at 19VDC VIN 100 100 LTC4006-4 95 95 EFFICIENCY (%) EFFICIE
PAGE 6
LTC4006 U U U PI FU CTIO S RT (Pin 4): Timer Resistor. The timer period is set by placing a resistor, RRT, to GND. CSP (Pin 9): Current Amplifier CA1 Input. This pin and the BAT pin measure the voltage across the sense resistor, RSENSE, to provide the instantaneous current signals required for both peak and average current mode operation. The timer period is tTIMER = (1hour • RRT/154k) If this resistor is not present, the charger will not start.
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LTC4006 W BLOCK DIAGRA VIN DCIN 25µA 1 0.1µF INFET Q3 2 CHG 100k VLOGIC 5.8V 16 CLN ACP/SHDN 3 TIMER/CONTROLLER OSCILLATOR 4 THERMISTOR 6 RRT RT ICL TBAD RESTART 32.4k NTC 1.105V 10k NTC 0.47µF LOBAT 397mV C/10 35mV 708mV – 5 3k + GND 11.67µA 10 BAT RSENSE 9 gm = 1m – + 1.19V Ω 15nF CLN – 11 – Ω 9k CL1 100mV 12 gm = 1.5m + RCL CLP 3k CA1 EA 5.1k 20µF CSP + gm = 1m Ω – CA2 + DCIN OSCILLATOR WATCH DOG DETECT tOFF 7 1.
PAGE 8
LTC4006 U OPERATIO Overview The LTC4006 is a synchronous current mode PWM stepdown (buck) switcher battery charger controller. The charge current is programmed by the sense resistor (RSENSE) between the CSP and BAT pins. The final float voltage is internally programmed to 8.4V (LTC4006-6), 12.6V (LTC4006-2) or 16.8V (LTC4006-4) with better than ±0.8% accuracy.
PAGE 9
LTC4006 U OPERATIO Table 1. Truth Table for LTC4006 Operation MODE DCIN BAT VOLTAGE BAT CURRENT ACP/SHDN TIMER STATE CHG* Shut Down by Low Adapter Voltage Conditioning a Depleted Battery BAT >UVLO <2.5V/Cell LOW HIGH Reset Running HIGH LOW Normal Charging >BAT >2.5V/Cell HIGH Running LOW Input Current Limited Charging >BAT >2.
PAGE 10
LTC4006 U OPERATIO Table 2. Truth Table for LTC4006 Operation (Supplemental) NUMBER FROM STATE TO STATE NEXT C/10 LATCH MAX BAT CURRENT ACP/SHDN TIMER STATE 1 Any MSD BAT 0 OFF HIGH Reset HIGH 3 SD Shut Down by Undervoltage Lockout >BAT and BAT <2.
PAGE 11
LTC4006 U OPERATIO be inhibited if it is not already active. If the charging current decreases below 10% to 15% of programmed current, while engaged in input current limiting, BGATE will be forced low to prevent the charger from discharging the battery. Audible noise can occur in this mode of operation. LTC4006 R9 32.4k – 6 RTH 10k NTC C7 0.47µF CLK NTC S1 + An overvoltage comparator guards against voltage transient overshoots (>7% of programmed value).
PAGE 12
LTC4006 U W U U APPLICATIO S I FOR ATIO Alternatively, a normally closed switch can be used to detect when the battery is present (see Figure 8). Charger Current Programming The basic formula for charging current is: 200 180 160 Table 3. Recommended RSENSE Resistor Values tTIMER (MINUTES) ICHARGE(MAX) 100mV = RSENSE 140 120 IMAX (A) RSENSE (Ω) 1% RSENSE (W) 1.0 0.100 0.25 2.0 0.050 0.25 3.0 0.033 0.5 40 4.0 0.025 0.
PAGE 13
LTC4006 U W U U APPLICATIO S I FOR ATIO Soft-Start The LTC4006 is soft started by the 0.12µF capacitor on the ITH pin. On start-up, ITH pin voltage will rise quickly to 0.5V, then ramp up at a rate set by the internal 40µA pull-up current and the external capacitor. Battery charging current starts ramping up when ITH voltage reaches 0.8V and full current is achieved with ITH at 2V. With a 0.
PAGE 14
LTC4006 U W U U APPLICATIO S I FOR ATIO Table 4 MAXIMUM AVERAGE CURRENT (A) INPUT VOLTAGE (V) MINIMUM INDUCTOR VALUE (µH) 1 ≤ 20 40 ±20% 1 > 20 56 ±20% 2 ≤ 20 20 ±20% 2 > 20 30 ±20% 3 ≤ 20 15 ±20% 3 > 20 20 ±20% 4 ≤ 20 10 ±20% 4 > 20 15 ±20% Charger Switching Power MOSFET and Diode Selection Two external power MOSFETs must be selected for use with the charger: a P-channel MOSFET for the top (main) switch and an N-channel MOSFET for the bottom (synchronous) switch.
PAGE 15
LTC4006 U W U U APPLICATIO S I FOR ATIO Example: VDCIN = 19V, fOSC = 345kHz, QG1 = QG2 = 15nC. PD = 292mW IDCIN = 5mA between the CLP and DCIN pins. When this voltage exceeds 100mV, the amplifier will override programmed charging current to limit adapter current to 100mV/RCL. A lowpass filter formed by 5kΩ and 15nF is required to eliminate switching noise. If the current limit is not used, CLP should be connected to CLN.
PAGE 16
LTC4006 U W U U APPLICATIO S I FOR ATIO LTC4006 LTC4006 R9 NTC 6 R9 NTC 6 C7 RTH C7 R9A 4006 F10 4006 F11 Figure 10. Voltage Divider Thermistor Network you, then simply set R9 = RTH(LOW) If you are using a thermistor that doesn’t have a 1:7 HIGH/ LOW ratio, or you wish to set the HIGH/LOW limits to different temperatures, then the more generic network in Figure 11 should work.
PAGE 17
LTC4006 U W U U APPLICATIO S I FOR ATIO selection. If the VIN supply is going to collapse very slowly such that Q1B is not turned on quickly enough for the given load and stay within its PD limits, you should install a suitable Schottky diode in parallel with Q1B. 100k VIN Q1A PCB Layout Considerations VOUT ZENER 18V TGATE Q1B INDUCTOR RSENSE VBAT 4006 F12 Figure 12. Optional Simple High Efficiency Battery Discharge Path 0V keeping Q1B in the off state while P-channel MOSFET Q1A is on.
PAGE 18
LTC4006 U W U U APPLICATIO S I FOR ATIO 4. Place the output current sense resistor right next to the inductor output but oriented such that the IC’s current sense feedback traces going to resistor are not long. The feedback traces need to be routed together as a single pair on the same layer at any given time with smallest trace spacing possible. Locate any filter component on these traces next to the IC and not at the sense resistor location. 8.
PAGE 19
LTC4006 U PACKAGE DESCRIPTION GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .189 – .196* (4.801 – 4.978) .045 ± .005 16 15 14 13 12 11 10 9 .254 MIN .009 (0.229) REF .150 – .165 .229 – .244 (5.817 – 6.198) .0165 ± .0015 .150 – .157** (3.810 – 3.988) .0250 BSC RECOMMENDED SOLDER PAD LAYOUT 1 .015 ± .004 × 45° (0.38 ± 0.10) .007 – .0098 (0.178 – 0.249) 2 3 4 5 6 7 .0532 – .0688 (1.35 – 1.75) 8 .004 – .0098 (0.102 – 0.249) 0° – 8° TYP .016 – .050 (0.
PAGE 20
LTC4006 U TYPICAL APPLICATIO 2A Li-Ion Battery Charger Q3 INPUT SWITCH DCIN 0V TO 20V 2.5A C1 0.1µF VLOGIC 1 R3 100k 2 CHG 3 ACP CHARGING CURRENT MONITOR 8 R9 32.4k 6 4 THERMISTOR 10k NTC C5 0.0047µF C7 0.47µF RT 309k TIMING RESISTOR (~2 HOURS) 7 R4 6.04k C6 0.12µF 5 16 INFET LTC4006 11 CHG CLP 12 CLN ACP/SHDN 13 TGATE IMON 15 BGATE NTC 14 PGND RT 9 CSP ITH 10 BAT GND DCIN D1: MBRM140T3 Q1, Q2: Si7501DN Q3: Si5435B R1 5k C4 15nF RCL 0.