Datasheet

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LTC4095

4095fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Standalone USB

Li-Ion/Polymer Battery

Charger in 2mm × 2mm DFN

The LTC

4095 is a complete constant-current/constant-

voltage linear charger for single-cell lithium-ion/polymer

batteries. Its small 2mm × 2mm DFN package and low

external component count make the LTC4095 especially

well-suited for portable USB power applications.

Up to 950mA of charge current may be programmed via a

single resistor from the PROG pin to ground. The HPWR

pin allows the charge current to be set at 20% or 100% of

its full-scale programmed value. An internal safety timer

terminates charge current. The ﬁ nal ﬂ oat voltage is preset

to 4.2V and held to a tight 0.5% tolerance. Also featured

is an NTC thermistor input to monitor battery temperature

while charging, a C/10 current detection output, automatic

recharge, bad-battery detection and low-battery trickle

charge. A thermal feedback loop regulates the charge

current to limit the die temperature during high power

operation or high ambient thermal conditions.

The LTC4095 is available in a tiny, low proﬁ le (0.75mm)

8-lead 2mm × 2mm DFN package.

■

Full-Featured Standalone USB Li-Ion/Polymer

Battery Charger

■

100mA to 950mA Programmable Charge Current

■

C/10 Charge Current Detection Output

■

Internal Safety Timer Termination

■

NTC Thermistor Input for Temperature Qualiﬁ ed

Charging

■

Preset 4.2V Float Voltage with 0.5% Accuracy

■

Constant-Current/Constant-Voltage Operation with

Thermal Feedback

■

Charge Current Monitor Output for Gas Gauging

■

Automatic Recharge

■

Bad-Battery Detection

■

8.5µA Input Supply Current in Suspend Mode

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Tiny 8-Lead (2mm × 2mm) DFN Package

■

PDAs

■

Media Players

■

Cellular Phones

■

Other Portable Electronics

, 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 6522118, 6570372, 6700364.

4095 TA01a

Li-Ion

BATTERY

PROG

1.74k

4.3V TO 5.5V

UP TO 7V

TRANSIENTS

1µF

LTC4095

CHRGHPWR

BAT

NTC

PROG

SUSP

GND

500mA Single-Cell Li-Ion Charger

Summary of content (16 pages)

PAGE 1
LTC4095 Standalone USB Li-Ion/Polymer Battery Charger in 2mm × 2mm DFN FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION Full-Featured Standalone USB Li-Ion/Polymer Battery Charger 100mA to 950mA Programmable Charge Current C/10 Charge Current Detection Output Internal Safety Timer Termination NTC Thermistor Input for Temperature Qualiﬁed Charging Preset 4.2V Float Voltage with 0.
PAGE 2
LTC4095 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Notes 1, 2, 3) Input Supply Voltage (IN) t < 1ms and Duty Cycle < 1% .................. –0.3V to 7V Steady State............................................. –0.3V to 6V BAT, SUSP, ⎯C⎯H⎯R⎯G Voltage ............................ –0.3V to 6V PROG, NTC, HPWR Voltage ............................ –0.3V to Max (IN, BAT) + 0.3V IBAT .............................................................................1A IPROG ....................................
PAGE 3
LTC4095 ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. IN = HPWR = 5V, BAT = 3.8V, NTC = SUSP = 0V, RPROG = 1.74k unless otherwise speciﬁed. SYMBOL PARAMETER CONDITIONS tRECHRG Recharge Comparator Filter Time BAT Falling MIN TYP MAX tTERM Safety Timer Termination Period BAT = VFLOAT 3.5 4 4.5 0.4375 0.5 0.5625 0.09 0.1 0.11 1.
PAGE 4
LTC4095 TYPICAL PERFORMANCE CHARACTERISTICS Battery Regulation (Float) Voltage vs Battery Charge Current Battery Regulation (Float) Voltage vs Temperature IN = 5V 4.24 RPROG = 0.845k HPWR = 5V 4.23 VBAT (V) VBAT (V) 4.22 4.20 4.19 4.18 4.17 Charge Current vs Supply Voltage (Constant Current Mode) 4.215 500 4.210 490 4.205 480 IBAT (mA) 4.25 4.21 TA = 25°C, unless otherwise noted. 4.200 IN = 5V RPROG = 1.74k HPWR = 5V 470 4.195 460 4.190 450 4.16 200 0 600 400 IBAT (mA) 800 4.
PAGE 5
LTC4095 TYPICAL PERFORMANCE CHARACTERISTICS Recharge Threshold vs Temperature TA = 25°C, unless otherwise noted. Undervoltage Lockout Threshold vs Temperature 115 4.2 SUSP/HPWR Pins Rising Threshold Voltage vs Temperature 1.2 BAT = 3.5V 1.1 4.1 UVLO THRESHOLD (V) ∆VRECHARGE (mV) 95 85 THRESHOLD VOLTAGE (V) RISING 105 4.0 3.9 FALLING 3.8 3.7 3.6 75 –55 –35 25 5 –15 45 TEMPERATURE (°C) 65 25 5 45 –15 TEMPERATURE (°C) 4095 G09 IN = 5V BAT = 4.
PAGE 6
LTC4095 PIN FUNCTIONS BAT (Pin 1): Single Cell Li-Ion Battery Pin. Provides charge current to the battery and regulates ﬁnal ﬂoat voltage to 4.2V. GND (Pin 2): Ground ⎯C⎯H⎯R⎯G (Pin 3): Open-Drain Charge Status Output. The ⎯C⎯H⎯R⎯G pin indicates the status of the battery charger. Four possible states are represented by ⎯C⎯H⎯R⎯G: charging, not charging (i.e., the charge current is less than 1/10th of the full-scale charge current), unresponsive battery (i.e., the battery voltage remains below 2.
PAGE 7
LTC4095 SIMPLIFIED BLOCK DIAGRAM 5 2.25MHz CLOCK 8 HPWR IN TREF TDIE COUNTER + – + RECHARGE BAT – + 2.9V 3 TRICKLE IBAT CHARGE CURRENT CONTROL CONTROL LOGIC BAT CONSTANT CURRENT/ CONSTANT VOLTAGE ENABLE TRICKLE CHARGE NTC TEMP FAULT CHRGR ON CHRG M1 BAT DUVLO IN NTC 1 + RECHRG – – 4.105V 6 THERMAL AMP BAD BAT TERMINATE CHARGE TEMP FAULT + 100mV IN IBAT 800 C/10 + – UVLO – BLINK LOGIC 4V SUSP PROG 7 4 GND 2 4095 F01 Figure 1.
PAGE 8
LTC4095 OPERATION Charge Cycle Overview Automatic Recharge When a battery charge cycle begins, the battery charger ﬁrst determines if the battery is deeply discharged. If the battery voltage is below VTRKL, typically 2.9V, an automatic trickle charge feature sets the battery charge current to 10% of the full-scale value. After the battery charger terminates, it will remain off, drawing only microamperes of current from the battery.
PAGE 9
LTC4095 OPERATION In any mode, the actual battery current can be determined by monitoring the PROG pin voltage and using the following equation: IBAT = PROG • 800 RPROG Thermal Regulation To prevent thermal damage to the IC or surrounding components, an internal thermal feedback loop will automatically decrease the programmed charge current if the die temperature rises to approximately 115°C.
PAGE 10
LTC4095 OPERATION NTC Thermistor The battery temperature is measured by placing a negative temperature coefﬁcient (NTC) thermistor close to the battery pack. The NTC circuitry is shown in Figure 3. To use this feature, connect the NTC thermistor, RNTC, between the NTC pin and ground, and a bias resistor, RNOM, from IN to NTC. RNOM should be a 1% resistor with a value equal to the value of the chosen NTC thermistor at 25°C (R25).
PAGE 11
LTC4095 APPLICATIONS INFORMATION Alternate NTC Thermistors and Biasing In the explanation below, the following notation is used. The LTC4095 provides temperature qualiﬁed charging if a grounded thermistor and a bias resistor are connected to the NTC pin. By using a bias resistor whose value is equal to the room temperature resistance of the thermistor (R25) the upper and lower temperatures are pre-programmed to approximately 40°C and 0°C, respectively (assuming a Vishay “Curve 1” thermistor).
PAGE 12
LTC4095 APPLICATIONS INFORMATION Solving these equations for RNTC|COLD and RNTC|HOT results in the following: RNTC|HOT = 0.536 • RNOM and RNTC|COLD = 3.25 • RNOM By setting RNOM equal to R25, the above equations result in rHOT = 0.536 and rCOLD = 3.25. Referencing these ratios to the Vishay Resistance-Temperature Curve 1 chart gives a hot trip point of about 40°C and a cold trip point of about 0°C. The difference between the hot and cold trip points is approximately 40°C.
PAGE 13
LTC4095 APPLICATIONS INFORMATION charge currents, the LTC4095 power dissipation is approximately: PD = (IN – BAT) • IBAT where PD is the power dissipated, IN is the input supply voltage, BAT is the battery voltage and IBAT is the charge current. It is not necessary to perform any worst-case power dissipation scenarios because the LTC4095 will automatically reduce the charge current to maintain the die temperature at approximately 115°C.
PAGE 14
LTC4095 APPLICATIONS INFORMATION In constant-current mode, the PROG pin is in the feedback loop rather than the battery voltage. Because of the additional pole created by any PROG pin capacitance, capacitance on this pin must be kept to a minimum. With no additional capacitance on the PROG pin, the battery charger is stable with program resistor values as high as 25k. However, additional capacitance on this node reduces the maximum allowed program resistor.
PAGE 15
LTC4095 PACKAGE DESCRIPTION DC Package 8-Lead Plastic DFN (2mm × 2mm) (Reference LTC DWG # 05-08-1719 Rev Ø) 0.70 ±0.05 2.55 ±0.05 1.15 ±0.05 0.64 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.45 BSC 1.37 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED R = 0.05 TYP 2.00 ±0.10 (4 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) R = 0.115 TYP 5 8 0.40 ± 0.10 0.64 ± 0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER (DC8) DFN 0106 REVØ 4 0.
PAGE 16
LTC4095 TYPICAL APPLICATION 500mA Single-Cell Li-Ion Charger IN 4.3V TO 5.5V UP TO 7V TRANSIENTS R1 510Ω LED CIN 1µF 100k IN LTC4095 CHRG SUSPEND 100 500 460mA BAT NTC SUSP PROG HPWR GND T 100k + Li-Ion BATTERY 1.