LTC4062 Standalone Linear Li-Ion Battery Charger with Micropower Comparator U FEATURES DESCRIPTIO ■ The LTC®4062 is a full-featured, flexible, standalone linear charger for single-cell Lithium-Ion batteries. It is capable of operating within USB power specifications. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Charge Current Programmable up to 1A Charges Single Cell Li-Ion Batteries Directly from USB Port Preset Float Voltage with ±0.35% Accuracy Micropower Comparator for Battery Monitoring Thermal Regulation Maximizes Charge Rate Without Risk of Overheating* Programmable Charge Current Detection/ Termination Programmable Charge Termination Timer Smart Pulsing Error Feature SmartStartTM Prolongs Battery Life 20µA Charger Quiescent Current in Shutdown Available in a Low Profile (0.75mm) 10-Lead (3mm × 3mm) DFN Package U APPLICATIO S ■ ■ ■ Handheld Computers Portable MP3 Players Digital Cameras , LTC and LT are registered trademarks of Linear Technology Corporation. SmartStart is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Protected by U.S. Patents, including 6522118. Both programmable time and programmable current based termination schemes are available. Furthermore, the CHRG open-drain status pin can be programmed to indicate the battery charge state according to the needs of the application. A precise low power comparator is available even with no power applied as long as battery voltage is higher than 2.5V. Additional safety features designed to maximize battery lifetime and reliability include the SmartStart charging algorithm. No external sense resistor or external blocking diode is required for charging due to the internal MOSFET architecture. Internal thermal feedback regulates the charge current to maintain a constant die temperature during high power operation or high ambient temperature conditions. The charge current is programmed with an external resistor. With power applied, the LTC4062 can be put into shutdown mode to reduce the supply current to 20µA and the battery drain current to less than 2µA. Without power applied, the internal low power comparator can work sinking only 10µA from the battery. Other features include smart recharge, USB C/5 current programming input and undervoltage lockout. U TYPICAL APPLICATIO Complete Charge Cycle (1100mAh Battery) VCC 1µF 619Ω OUT LTC4062 EN C/5 BAT TIMER PROG IDET IN+ GND BAT > 3V BAT < 3V 100k 800mA 715k + 347k SINGLE CELL Li-Ion BATTERY 900 4.3 800 4.2 700 4.1 600 4.0 3.9 500 BATTERY VOLTAGE 400 3.8 3.7 300 3.6 200 VCC = 5V TA = 25°C 100 4062 TA01 BATTERY CURRENT BATTERY VOLTAGE (V) VIN 4.3V TO 8V CHARGE CURRENT (mA) 800mA Single Cell Li-Ion Battery Charger (C/10 Termination) 3.5 0 0 0.5 1.5 1.0 2.0 TIME (HOURS) 2.5 3.4 3.0 4062 TA01b 4062f 1 LTC4062 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART NUMBER TOP VIEW Input Supply Voltage (VCC) ........................ –0.3V to 10V EN, OUT, CHRG, IN+, PROG, C/5, BAT ....... –0.3V to 10V TIMER, IDET ..................................... –0.3V to VCC +0.3V BAT Short-Circuit Duration ...........................Continuous VCC Pin Current ......................................................... 1A BAT Pin Current ......................................................... 1A Maximum Junction Temperature .......................... 125°C Operating Temperature Range (Note 2) ... –40°C to 85°C Storage Temperature Range .................. –65°C to 125°C 10 VCC BAT IN+ 1 TIMER 3 OUT 4 8 IDET 7 EN CHRG 5 6 C/5 9 PROG 2 11 LTC4062EDD DD PART MARKING DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 40°C/W (NOTE 3) EXPOSED PAD IS GROUND (PIN 11) MUST BE SOLDERED TO PCB LBJT Consult LTC Marketing for parts specified with wider operating temperature ranges. 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. SYMBOL PARAMETER VCC Input Supply Voltage ICC Input Supply Current VFLOAT VBAT Regulated Output Voltage CONDITIONS MIN ● Charge Mode (Note 4), RPROG = 10k Standby Mode, Charge Terminated Shutdown (EN = 5V, VCC < VBAT or VCC < VUV) TYP MAX 8 V 240 130 20 500 300 50 µA µA µA 4.185 4.175 4.2 4.2 4.215 4.225 V V 93 760 100 800 ±1 ±1 107 840 ±2 ±2 mA mA µA µA 0.97 0.97 1 1 1.03 1.03 V V 0.10 0.16 0.25 0.26 V V 4.3 ● ● ● 0 < TA < 85°C ● ● ● ● UNITS IBAT BAT Pin Current RPROG = 10k, Constant Current Mode RPROG = 1.25k, Constant Current Mode Standby Mode, Charge Terminated Shutdown Mode VPROG PROG Pin Voltage RPROG = 10k, Constant Current Mode RPROG = 1.25k, Constant Current Mode VOUT OUT Output Low Voltage IOUT = 5mA IOUT = 5mA, VCC = 0V, VBAT = 2.55V VCHRG CHRG Output Low Voltage ICHRG = 5mA 0.1 0.25 V ITRIKL Trickle Charge Current VBAT < VTRIKL, RPROG = 10k VBAT < VTRIKL, RPROG = 1.25k 6 60 10 80 14 100 mA mA VTRIKL Trickle Charge Threshold Voltage VBAT Rising Hysteresis 2.8 2.9 100 3 V mV VUV VCC Undervoltage Lockout Voltage From Low to High Hysteresis 3.7 3.8 200 3.9 V V VASD VCC – VBAT Lockout Threshold Voltage VCC from Low to High, VBAT = 4.3V VCC from High to Low, VBAT = 4.3V 145 10 190 45 230 75 mV mV REN EN Pin Pull-Down Resistor 2 3.4 5 MΩ VEN EN Input Threshold Voltage EN Rising, 4.3V < VCC < 8V Hysteresis 0.4 0.7 70 1 V mV VCT Charge Termination Mode Threshold Voltage VTIMER from High to Low Hysteresis 0.4 0.7 50 1 V mV VUT User Termination Mode Threshold Voltage VTIMER from Low to High Hysteresis 3.9 4.2 50 ● V mV 4062f 2 LTC4062 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. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IDETECT Charge Current Detection Threshold RDET = 1k, 0 ≤ TA ≤ 85°C RDET = 2k, 0 ≤ TA ≤ 85°C RDET = 10k, 0 ≤ TA ≤ 85°C RDET = 20k, 0 ≤ TA ≤ 85°C 90 45 8 3.8 100 50 10 5 110 55 12 6.2 mA mA mA mA ∆VRECHRG Recharge Threshold Voltage VFLOAT – VRECHRG, 0 ≤ TA ≤ 85°C 65 100 135 mV tSS Soft-Start Time IBAT from 0 to ICHG tTERM Termination Comparator Filter Time Current Termination Mode tRECHRG Recharge Comparator Filter Time tTIMER Charge Cycle Time RC/5 C/5 Pin Pull-Down Resistor VC/5 C/5 Input Threshold Voltage TLIM Junction Temperature in Constant Temperature Mode RON Power FET “ON” Resistance (Between VCC and BAT) VBAT = 3.85V, ICC = 175mA, RPROG = 2k VIN+ IN+ Pin Threshold Voltage VIN+ Falling Hysteresis VBAT-MIN Minimum VBAT Supply Voltage for the Low Power Comparator IBAT Supply Current for the Low Power Comparator 100 CTIMER = 0.1µF ● C/5 Rising, 4.3V < VCC < 8V Hysteresis µs 0.8 1.5 2.5 ms 3 7 14 ms 2.55 3 3.45 2 3.4 5 MΩ 0.4 0.7 70 1 V mV hr 105 °C 375 mΩ Comparator ● 0.988 1 50 1.012 V mV VCC = 0V, VBAT Falling Hysteresis 2.4 2.5 100 2.6 V mV VCC = 0V, VBAT = 2.5V 7 9 13 µA Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The LTC4062 is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Failure to correctly solder the exposed pad of the package to the PC board will result in a thermal resistance much higher than 40°C/W. Note 4: Supply current includes PROG pin current and IDET pin current (approximately 100µA each) but does not include any current delivered to the battery through the BAT pin (approximately 100mA). Note 5: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Overtemperature protection will become active at a junction temperature greater than the maximum operating temperature. Continuous operation above the specified maximum operating junction temperature may impair device reliability. 4062f 3 LTC4062 U W TYPICAL PERFOR A CE CHARACTERISTICS Battery Regulated Output (Float) Voltage vs Charge Current 4.26 Battery Regulated Output (Float) Voltage vs Temperature 4.215 VCC = 5V RPROG = 1k 4.24 TA = 25°C unless otherwise noted Battery Regulated Output (Float) Voltage vs Supply Voltage 4.26 VCC = 5V RPROG = 10k 4.210 4.22 4.22 VFLOAT (V) VFLOAT (V) 4.18 4.16 VFLOAT (V) 4.205 4.20 4.200 4.18 4.16 4.14 4.190 4.12 4.10 200 800 600 CHARGE CURRENT (mA) 0 400 4.12 4.185 –50 1000 –25 0 25 50 TEMPERATURE (°C) 75 1.006 800 1.006 RPROG = 10k C/5 = VCC 1.002 VPROG (V) VPROG (V) VCC = 8V 1.000 VCC = 4.3V 1.000 400 0.998 0.998 200 0.996 0.996 0.2 0.4 0.6 0.8 1.0 1.2 0.994 –50 –25 VPROG (V) 0 25 50 TEMPERATURE (°C) 75 84 100 0.994 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Trickle Charge Threshold Voltage vs Temperature 2.96 8.0 4062 G06 4062 G05 VCC = 5V VBAT = 2.5V RPROG = 1.25k 7.5 VCC (V) 4062 G04 Trickle Charge Current vs Temperature 8.0 VCC = 5V VBAT = 4V RPROG = 10k C/5 = 5V 1.004 1.002 0 7.0 7.5 PROG Pin Voltage vs VCC (Constant-Current Mode) 1.004 600 6.0 6.5 4062 G03 PROG Pin Voltage vs Temperature (Constant-Current Mode) VCC = 5V RPROG = 1k C/5 = 5V VTIMER = 5V 1000 5.0 5.5 4062 G02 Charge Current vs PROG Pin Voltage 1200 4.10 4.0 4.5 100 VCC (V) 4062 G01 IBAT (mA) 4.20 4.195 4.14 0 RPROG = 1k TA = 25°C IBAT = 10mA 4.24 Charge Current vs Battery Voltage 550 VCC = 5V RPROG = 1.25k C/5 = 5V 2.94 450 80 IBAT (mA) 2.92 VTRICKLE (V) ITRICKLE (mA) 82 2.90 350 250 2.88 78 76 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 4062 G07 2.84 –50 VCC = 5V RPROG = 2k 150 2.86 –25 0 25 50 TEMPERATURE (°C) 75 100 4062 G08 C/5 = 0V 50 3.2 3.0 3.6 3.4 VBAT (V) 3.8 4.0 4062 G09 4062f 4 LTC4062 U W TYPICAL PERFOR A CE CHARACTERISTICS Charge Current vs Ambient Temperature with Thermal Regulation Internal Charge Timer vs Temperature 195 Charge Current vs Supply Voltage 1000 104 VCC = 5V VBAT = 4V C/5 = 5V RPROG = 10k ONSET OF THERMAL REGULATION 190 tTIMER (MINUTES) TA = 25°C unless otherwise noted VCC = 4.3V 800 VCC = 8V 600 RPROG = 1.25k 102 180 IBAT (mA) IBAT (mA) 185 RPROG = 2k 400 100 175 200 170 165 –50 CTIMER = 0.1µF –25 0 25 50 TEMPERATURE (°C) 75 98 VCC = 5V VBAT = 4V θJA = 40°C/W 0 –50 100 50 25 0 75 TEMPERATURE (°C) –25 100 96 125 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 4062 G10 4062 G13 Recharge Threshold Voltage vs Temperature 4062 G14 Power FET “ON” Resistance vs Temperature 4.16 500 4.14 450 8.0 VCC (V) Undervoltage Lockout Voltage vs Temperature 3.900 VCC = 4V IBAT = 200mA 3.875 3.850 VCC = 8V 4.10 VCC = 4.3V 3.825 400 VUV (V) RDS(ON) (mΩ) VRECHARGE (V) 4.12 350 3.775 4.08 3.750 300 4.06 3.725 4.04 –50 –25 0 25 50 TEMPERATURE (°C) 75 250 –50 100 –25 0 25 50 TEMPERATURE (°C) 75 700 REN (MΩ) 600 500 400 300 –25 50 25 0 TEMPERATURE (°C) 100 75 4062 G17 C/5 Pin Pulldown Resistance vs Temperature 5.0 5.0 4.5 4.5 4.0 4.0 RC/5 (MΩ) VCC = 5V C/5 = 5V RPROG = 1.25k θJA = 40°C/W 800 3.700 – 50 EN Pin Pulldown Resistance vs Temperature Charge Current vs Battery Voltage 900 100 4062 G16 4062 G15 IBAT (mA) 3.800 3.5 3.5 3.0 3.0 2.5 2.5 200 100 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 VBAT (V) 4062 G18 2.0 –50 –25 50 25 0 TEMPERATURE (°C) 75 100 4062 G19 2.0 –50 –25 50 25 0 TEMPERATURE (°C) 75 100 4062 G20 4062f 5 LTC4062 U W TYPICAL PERFOR A CE CHARACTERISTICS EN Pin Threshold Voltage (On-to-Off) vs Temperature Shutdown Supply Current vs Temperature and VCC C/5 Pin Threshold Voltage (High-to-Low) vs Temperature 900 900 VCC = 5V 70 VCC = 5V EN = VCC 850 60 800 800 50 750 ICC (µA) 850 VC/5 (mV) VEN (mV) TA = 25°C unless otherwise noted 750 40 700 700 30 650 650 20 600 –50 600 –50 10 –50 VCC = 8V VCC = 5V VCC = 4.3V –25 0 25 50 TEMPERATURE (°C) 75 100 –25 50 25 0 TEMPERATURE (°C) 100 4062 G23 0.6 VCC = 5V VBAT = 4V TA = –40°C 120 VCC = 5V ICHRG = 5mA 0.5 TA = 25°C 0.4 TA = 90°C 100 VCHRG (V) IOUT (mA) 75 CHRG Pin Output Low Voltage vs Temperature OUT Pin I-V Curve 140 0 25 50 TEMPERATURE (°C) –25 4062 G22 4062 G21 160 100 75 80 60 0.3 0.2 40 0.1 20 0 0 2 1 3 0 –50 4 50 25 0 TEMPERATURE (°C) –25 VOUT (V) 4062 G25 4062 G24 OUT Pin Output Low Voltage vs Temperature 0.6 0.5 CHRG Pin I-V Curve 160 VCC = 5V IOUT = 5mA IN+ ≥ 1.05V VCC = 5V VBAT = 4V 140 TA = –40°C 120 ICHRG (mA) 0.4 VOUT (V) 100 75 0.3 0.2 TA = 25°C TA = 90°C 100 80 60 40 0.1 0 –50 20 –25 50 25 0 TEMPERATURE (°C) 75 100 4062 G26 0 0 1 2 VCHRG (V) 3 4 4062 G27 4062f 6 LTC4062 U U U PI FU CTIO S BAT (Pin 1): Charge Current Output. This pin provides charge current to the battery and regulates the final float voltage to 4.2V. IN+ (Pin 2): Positive Input of the Micropower Comparator. The negative input is tied internally to a precise bandgap voltage reference of 1V. There is approximately 50mV of hysteresis associated with the input comparator threshold (rising edge). TIMER (Pin 3): Timer Program and Termination Select Pin. This pin selects which method is used to terminate the charge cycle. Connecting a capacitor, CTIMER, to ground selects charge time termination. The charge time is set by the following formula: CTIMER or 0.1µF TIME (HOURS) CTIMER = 0.1µF • 3 (HOURS) TIME (HOURS) = 3 (HOURS) • Connecting the TIMER pin to ground selects charge current termination, while connecting the pin to VCC selects user termination. See Applications Information for more information on current and user termination. OUT (Pin 4): Low Power Comparator Open-Drain Output. This comparator output pin has two states; pull-down and high impedance. This output can be used as a logic interface or as an LED driver. In the pull-down state, an NMOS transistor capable of sinking 10mA pulls down on the OUT pin. The state of this pin is dependent on the value of IN+. When IN+ is greater than 1V the output pin is in pulldown state, if IN+ is less than 1V the output pin is in high impedance state. See Applications Information. CHRG (Pin 5): Open-Drain Charge Status Output. The charge status indicator pin has three states: pull-down, pulse at 6Hz and high impedance. This output can be used as a logic interface or as a LED driver. In the pull-down state, an NMOS transistor capable of sinking 10mA pulls down on the CHRG pin. The state of this pin depends on the value of IDETECT as well as the termination method being used. See Applications Information. C/5 (Pin 6): C/5 Enable Input. Used to control the amount of current drawn by the charger when powered from a USB port. A logic high on the C/5 pin sets the current limit to 100% of the current programmed by the PROG pin. A logic low on the C/5 pin sets the current limit to 20% of the current programmed by the PROG pin. An internal 3MΩ pull-down resistor defaults the C/5 pin to its low current state. EN (Pin 7): Charger Enable Input. A logic high on the EN pin places the charger into shutdown mode, where the input quiescent current is less than 50µA. A logic low on this pin enables charging. An internal 3MΩ pull-down resistor to ground defaults the charger to its enabled state. IDET (Pin 8): Current Detection Threshold Program Pin. The current detection threshold, IDETECT, is set by connecting a resistor, RDETECT, to ground. IDETECT is set by the following formula: RPROG 100V • ICHG = or 10RDET RDET 100V IDETECT = RDET = IDETECT The CHRG pin becomes high impedance when the charge current drops below IDETECT. IDETECT can be set to 1/10th the programmed charge current by connecting IDET directly to PROG. If the IDET pin is not connected, the CHRG output remains in its pull-down state until the charge time elapses and terminates the charge cycle. See Applications Information. This pin is clamped to approximately 2.4V. Driving this pin to voltages beyond the clamp voltage should be avoided. PROG (Pin 9): Charge Current Program and Charge Current Monitor. The charge current is set by connecting a resistor, RPROG, to ground. When charging in constant current mode, this pin servos to 1V. The voltage on this pin can be used to measure the charge current using the following formula: IBAT = VPROG • 1000 RPROG 4062f 7 LTC4062 U U U PI FU CTIO S VCC (Pin 10): Positive Input Supply Voltage. Provides power to the battery charger. This pin should be bypassed with a 1µF capacitor. GND (Exposed Pad) (Pin 11): Ground. This pin is the back of the exposed metal pad package and must be soldered to the PCB copper for minimal thermal resistance. W BLOCK DIAGRA 10 VCC + 4.1V – TO BAT 2 C1 1× 1× IN+ 1000× – BAT + 1 MA OUT + 4 C4 CA – 5 1V – VA + + – CHRG 1V 1.2V STOP 0.2V RECHRG 6 0.1V C/5 C/5 LOGIC 3M LOGIC 7 EN TERM EN C/5 3M SEL C2 + C3 + – TO BAT 2.9V – COUNTER 0.1V OSCILLATOR + TDIE – 105°C TA SHDN IDET TIMER 3 8 PROG 9 GND 11 4062 BD CTIMER RDET RPROG 4062f 8 LTC4062 U OPERATIO The LTC4062 is designed to charge single cell lithium-ion batteries. Using the constant current/constant voltage algorithm, the charger can deliver up to 1A of charge current with a final float voltage accuracy of ±0.35%. The LTC4062 includes an internal P-channel power MOSFET and thermal regulation circuitry. No blocking diode or external sense resistor is required; thus, the basic charger circuit requires only two external components. Normal Operation The charge cycle begins when the voltage at the VCC pin rises above the UVLO level and a discharged battery is connected to BAT. If the BAT pin voltage is below 2.9V, the charger enters trickle charge mode. In this mode, the LTC4062 supplies 1/10th of the programmed charge current in order to bring the battery voltage up to a safe level for full current charging. Once the BAT pin voltage rises above 2.9V, the charger enters constant current mode, where the programmed charge current is supplied to the battery. When the BAT pin approaches the final float voltage (4.2V), the LTC4062 enters constant voltage mode and the charge current decreases as the battery becomes fully charged. The LTC4062 offers several methods with which to terminate a charge cycle. Connecting an external capacitor to the TIMER pin activates an internal timer that stops the charge cycle after the programmed time period has elapsed. Grounding the TIMER pin and connecting a resistor to the IDET pin causes the charge cycle to terminate once the charge current falls below a set threshold when the charger is in constant voltage mode. Connecting the TIMER pin to VCC disables internal termination, allowing external charge user termination through the EN input. See Applications Information for more information on charge termination methods. Programming Charge Current The charge current is programmed using a single resistor from the PROG pin to ground. When the charger is in the constant current mode, the voltage on the PROG pin is 1V. The battery charge current is 1000 times the current out of the PROG pin. The program resistor and the charge current are calculated by the following equations: RPROG = 1000 V 1000 V , ICHG = ICHG RPROG The charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage and applying the following equation: IBAT = VPROG • 1000 RPROG SmartStart When the LTC4062 is initially powered on or brought out of shutdown mode, the charger checks the battery voltage. If the BAT pin is below the recharge threshold of 4.1V (which corresponds to approximately 80-90% battery capacity), the LTC4062 enters charge mode and begins a full charge cycle. If the BAT pin is above 4.1V, the LTC4062 enters standby mode and does not begin charging. This feature reduces the number of unnecessary charge cycles, prolonging battery life. Automatic Recharge When the charger is in standby mode, the LTC4062 continuously monitors the voltage on the BAT pin. When the BAT pin voltage drops below 4.1V, the charge cycle is automatically restarted and the internal timer is reset to 50% of the programmed charge time (if time termination 4062f 9 LTC4062 U OPERATIO is being used). This feature eliminates the need for periodic charge cycle initiations and ensures that the battery is always fully charged. Automatic recharge is disabled in user termination mode. Thermal Regulation An internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 105°C. This feature protects the LTC4062 from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damaging the LTC4062. The charge current can be set according to typical (not worst-case) ambient temperatures with the assurance that the charger will automatically reduce the current in worst-case conditions. Undervoltage Lockout (UVLO) An internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until VCC rises above the undervoltage lockout threshold (3.8V). The UVLO circuit has a built-in hysteresis of 200mV. Furthermore, to protect against reverse current in the power MOSFET, the UVLO circuit keeps the charger in shutdown mode if VCC falls to less than 45mV above the battery voltage. Hysteresis of 145mV prevents the charger from cycling in and out of shutdown. Manual Shutdown At any point in the charge cycle, the charger can be put into shutdown mode by pulling the EN pin high. This reduces the supply current to less than 50µA and the battery drain current of the charger to less than 2µA. A new charge cycle can be initiated by floating the EN pin or pulling it low. If shutdown is not required, leaving the pin disconnected continuously enables the circuit. Trickle-Charge and Defective Battery Detection When the BAT pin voltage is below the 2.9V trickle charge threshold (VTRIKL), the charger reduces the charge current to 10% of the programmed value. If the battery remains in trickle charge for more than 25% of the total programmed charge time, the charger stops charging and enters a FAULT state, indicating that the battery is defective1. The LTC4062 indicates the FAULT state by driving the CHRG open-drain output with a square wave. The duty cycle of this oscillation is 50% and the frequency is set by CTIMER: fCHRG = 0.1µF • 6Hz CTIMER A LED driven by the CHRG output exhibits a pulsing pattern, indicating to the user that the battery needs replacing. To exit the FAULT state, the charger must be restarted either by toggling the EN input or removing and reapplying power to VCC. Charge Status Output (CHRG) The charge status indicator pin has three states: pulldown, pulse at 6Hz and high impedance. In the pull-down state, an NMOS transistor pulls down on the CHRG pin capable of sinking up to 10mA. A pull-down state indicates that the LTC4062 is charging a battery and the charge current is greater than IDETECT (which is set by the external component RDET). A high impedance state indicates that the charge current has dropped below IDETECT. In the case where the IDET pin is left unconnected (RDET = ∞, IDETECT = 0), a high impedance state on CHRG indicates that the LTC4062 is not charging. 1The Defective Battery Detection Feature is only available when time termination is being used. 4062f 10 LTC4062 U OPERATIO Smart Pulsing Error Feature LTC4062 has a pulsing state at the CHRG pull-down pin of 6Hz (50% duty cycle) due to defective battery detection (see Trickle-Charge and Defective Battery Detection section). Low Power Comparator (IN+; OUT) The low power, low offset comparator is designed with an internal 1V reference connected to the negative input. This reference is generated by a precise bandgap circuit. The comparator output drives a pull down NMOS transistor able to sink up to 10mA. Voltages lower than 1V at the IN+ pin set the OUT pin to a high impedance state. Voltages higher than 1V plus a built-in 50mV hysteresis at the IN+ pin set the OUT pin to a low impedance state. The comparator is operational even when VCC is not applied provided the BAT pin voltage is greater than 2.5V. When the voltage at the BAT pin drops below 2.5V, the comparator shuts down and the current at the BAT pin is reduced to <1µA. 4 2 OUT IN+ + 1V – LTC4062 4062 F01 Figure 1. Low Power Comparator Circuit 4062f 11 LTC4062 U W U U APPLICATIO S I FOR ATIO Programming Charge Termination The LTC4062 can terminate a charge cycle using one of several methods, allowing the designer considerable flexibility in choosing an ideal charge termination algorithm. Table 1 shows a brief description of the different termination methods and their behaviors. Charge Time Termination Connecting a capacitor (CTIMER) to the TIMER pin enables the timer and selects charge time termination. The total charge time is set by: TIME (HOURS) = CTIMER • 3 HOURS 0.1µF When the programmed time has elapsed, the charge cycle terminates and the charger enters standby mode. Subsequent recharge cycles terminate when 50% of the programmed time has elapsed. The IDET pin determines the behavior of the CHRG output. Connecting a resistor (RDET) from the IDET pin to ground sets the charge current detection threshold, IDETECT: RPROG 100V • ICHG = or 10RDET RDET 100V IDETECT = RDET = IDETECT When the charge current (I BAT ) is greater than IDETECT, the CHRG output is in its pull-down state. When the charger enters constant voltage mode operation and the charge current falls below IDETECT, the CHRG output becomes high impedance, indicating that the battery is almost fully charged. The CHRG output will also become high impedance once the charge time elapses. If the IDET pin is not connected, the CHRG output remains in its pulldown state until the charge time elapses and terminates the charge cycle. Figure 2 shows a charger circuit using charge time termination that is programmed to charge at 500mA. Once the charge current drops below 100mA in constant voltage mode (as set by RDET), the CHRG output turns off the LED. This indicates to the user that the battery is almost fully charged and ready to use. The LTC4062 continues to Table 1 METHOD Charge Time Termination Mode Charge Current Termination User Selectable Charge Termination TIMER 0.1µF to GND IDET RDET to GND CHARGER DESCRIPTION Charges for 3 Hours. After 3 Hours, the Charger Stops Charging and Enters Standby Mode. Recharge Cycles Last for 1.5 Hours. CHRG OUTPUT DESCRIPTION Pull-Down State While IBAT > IDET. High Impedance State While IBAT < IDETECT or When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. 0.1µF to GND NC Charges for 3 Hours. After 3 Hours, the Charger Stops Charging and Enters Standby Mode. Recharge Cycles Last for 1.5 Hours. Pull-Down State When Charging. High Impedance State When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. GND RDET to GND Charges Until Charge Current Drops Below IDET, Then Enters Standby Mode. GND NC VCC RDET to GND Charges Indefinitely. SmartStart Is Disabled. Pull-Down State When Charging. High Impedance State When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. Pull-Down State When Charging. High Impedance State When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. Pull-Down State While IBAT > IDETECT. High Impedance State While IBAT < IDETECT or When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. VCC NC Charges Indefinitely. SmartStart Is Disabled. Charges Indefinitely. Pull-Down State When Charging. High Impedance State When Charging Is Stopped. Pulsing State Available When NTC Is Used and Is Still Charging. 4062f 12 LTC4062 U W U U APPLICATIO S I FOR ATIO charge the battery until the internal timer reaches 3 hours (as set by CTIMER). During recharge cycles, the LTC4062 charges the battery until the internal timer reaches 1.5 hours. Figure 3 describes the operation of the LTC4062 charger when charge time termination is used. Charge Current Termination Connecting the TIMER pin to ground selects charge current termination. With this method, the timer is disabled and a resistor (RDET) must be connected from the IDET pin to ground. IDETECT is programmed using the same equation stated in the previous section. The charge cycle terminates when the charge current falls below IDETECT. This condition is detected using an internal filtered comparator to monitor the IDET pin. When the IDET pin falls below 100mV for longer than tTERM (typically 1.5ms), charging is terminated. 500mA VIN VCC BAT C/5 LTC4062 CHRG PROG RPROG 2k IDET RDET 1k + TIMER GND CTIMER 0.1µF 4062 F02 When charging, transient loads on the BAT pin can cause the IDET pin to fall below 100mV for short periods of time before the DC current has dropped below the IDETECT Figure 2. Time Termination Mode. The Charge Cycle Ends After 3 Hours POWER ON DEFECTIVE BATTERY FAULT MODE NO CHARGE CURRENT CHRG STATE: PULSING 1/4 CHARGE TIME ELAPSES EN = 0V OR UVLO CONDITION STOPS TRICKLE CHARGE MODE 1/10TH FULL CURRENT CHRG STATE: PULL-DOWN BAT < 2.9V BAT > 2.9V CHARGE MODE SHUTDOWN MODE FULL CURRENT ICC DROPS TO 20µA CHRG STATE: 2.9V < BAT < 4.1V PULL-DOWN IF IBAT > IDETECT Hi-Z IF IBAT < IDETECT CHRG STATE: Hi-Z CHARGE TIME ELAPSES STANDBY MODE BAT > 4.1V NO CHARGE CURRENT EN = 5V OR UVLO CONDITION CHRG STATE: Hi-Z BAT < 4.1V RECHARGE MODE FULL CURRENT 1/2 CHARGE TIME ELAPSES CHRG STATE: PULL-DOWN IF IBAT > IDETECT Hi-Z IF IBAT < IDETECT 4062 F03 Figure 3. State Diagram of a Charge Cycle Using Charge Time Termination 4062f 13 LTC4062 U W U U APPLICATIO S I FOR ATIO threshold. The 1.5ms filter time (tTERM) on the internal comparator ensures that transient loads of this nature do not result in premature charge cycle termination. Once the average charge current drops below IDETECT, the charger terminates the charge cycle. When the charger is set for charge current termination and the battery is removed from the charger, a sawtooth waveform of several hundred mV will appear at the charger output. This is caused by the repeated cycling between termination and recharge events. This cycling results in pulsing at the CHRG output. If an LED is connected to this pin, it will exhibit a pulsing pattern, indicating to the user that a battery is not present. The frequency of the sawtooth is dependent on the amount of output capacitance. The CHRG output is in a pull-down state while charging and in a high impedance state once charging has stopped. Figure 4 describes the operation of the LTC4062 charger when charge current termination is used. POWER ON TRICKLE CHARGE MODE 1/10TH FULL CURRENT EN = 0V OR UVLO CONDITION STOPS CHRG STATE: PULL-DOWN BAT < 2.9V BAT > 2.9V 2.9V < BAT < 4.1V CHARGE MODE SHUTDOWN MODE FULL CURRENT ICC DROPS TO 20µA CHRG STATE: Hi-Z CHRG STATE: PULL-DOWN IBAT < IDETECT IN VOLTAGE MODE BAT < 4.1V STANDBY MODE NO CHARGE CURRENT EN = 5V OR UVLO CONDITION CHRG STATE: Hi-Z BAT > 4.1V 4062 F04 Figure 4. State Diagram of a Charge Cycle Using Charge Current Termination POWER ON EN = 0V OR UVLO CONDITION STOPS TRICKLE CHARGE MODE 1/10TH FULL CURRENT SHUTDOWN MODE CHRG STATE: PULL-DOWN ICC DROPS TO 20µA BAT < 2.9V BAT > 2.9V CHRG STATE: Hi-Z CHARGE MODE FULL CURRENT CHRG STATE: 2.9V < BAT PULL-DOWN IF IBAT > IDETECT Hi-Z IF IBAT < IDETECT 4062 F05 EN = 5V OR UVLO CONDITION Figure 5. State Diagram of a Charge Cycle Using User-Selectable Termination 4062f 14 LTC4062 U W U U APPLICATIO S I FOR ATIO User-Selectable Charge Termination Connecting the TIMER pin to VCC selects user-selectable charge termination, in which all of the internal termination features are disabled. The charge cycle continues indefinitely until the charger is shut down through the EN pin. The IDET pin programs the behavior of the CHRG output in the same manner as when using charge time termination. If the IDET pin is not connected, the CHRG output remains in its pull-down state until the charger is shut down. With user-selectable charge termination, the SmartStart feature is disabled; when the charger is powered on or enabled, the LTC4062 automatically begins charging, regardless of the battery voltage. Figure 5 describes charger operation when user-selectable charge termination is used. Programming C/10 Current Detection/Termination In most cases, an external resistor, RDET, is needed to set the charge current detection threshold, IDETECT. However, when setting IDETECT to be 1/10th of ICHG, the IDET pin can be connected directly to the PROG pin. This reduces the component count, as shown in Figure 6. 500mA VIN VCC BAT C/5 LTC4062 PROG RPROG 2k IDET TIMER GND VCC BAT RDET 2k + 500mA VIN C/5 LTC4062 PROG RPROG 1k IDET + TIMER GND When PROG and IDET are connected in this way, the fullscale charge current, ICHG, is programmed with a different equation: RPROG = 500V 500V , ICHG = ICHG RPROG Stability Considerations The battery charger constant voltage mode feedback loop is stable without any compensation provided a battery is connected. However, a 1µF capacitor with a 1Ω series resistor to GND is recommended at the BAT pin to reduce noise when no battery is present. When the charger is in constant current mode, the PROG pin is in the feedback loop, not the battery. The constant current stability is affected by the impedance at the PROG pin. With no additional capacitance on the PROG pin, the charger is stable with program resistor values as high as 10kΩ; however, additional capacitance on this node reduces the maximum allowed program resistor value. Power Dissipation When designing the battery charger circuit, it is not necessary to design for worst-case power dissipation scenarios because the LTC4062 automatically reduces the charge current during high power conditions. The conditions that cause the LTC4062 to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the IC. Most of the power dissipation is generated from the internal charger MOSFET. Thus, the power dissipation is calculated to be approximately: PD = (VCC – VBAT) • IBAT 4062 F06 Figure 6. Two Circuits That Charge at 500mA Full-Scale Current and Terminate at 50mA PD is the power dissipated, VCC is the input supply voltage, VBAT is the battery voltage and IBAT is the charge current. The approximate ambient temperature at which the thermal feedback begins to protect the IC is: TA = 105°C – PD • θJA TA = 105°C – (VCC – VBAT) • IBAT • θJA 4062f 15 LTC4062 U W U U APPLICATIO S I FOR ATIO Example: An LTC4062 operating from a 5V wall adapter is programmed to supply 800mA full-scale current to a discharged Li-Ion battery with a voltage of 3.3V. Assuming θJA is 40°C/W (see Thermal Considerations), the ambient temperature at which the LTC4062 will begin to reduce the charge current is approximately: TA = 105°C – (5V – 3.3V) • (800mA) • 40°C/W TA = 105°C – 1.36W • 40°C/W = 105°C – 54.4°C TA = 50.6°C The LTC4062 can be used above 50.6°C ambient, but the charge current will be reduced from 800mA. The approximate current at a given ambient temperature can be approximated by: IBAT = 105°C – TA (VCC – VBAT )• θ JA Using the previous example with an ambient temperature of 60°C, the charge current will be reduced to approximately: 105°C – 60°C 45°C = (5V – 3.3V)• 40°C /W 68°C /A = 662mA IBAT = IBAT It is important to remember that LTC4062 applications do not need to be designed for worst-case thermal conditions, since the IC will automatically reduce power dissipation if the junction temperature reaches approximately 105°C. Thermal Considerations In order to deliver maximum charge current under all conditions, it is critical that the exposed metal pad on the backside of the LTC4062 package is properly soldered to the PC board ground. Correctly soldered to a 2500mm2 double sided 1oz copper board, the LTC4062 has a thermal resistance of approximately 40°C/W. Failure to make thermal contact between the exposed pad on the backside of the package and the copper board will result in thermal resistances far greater than 40°C/W. As an example, a correctly soldered LTC4062 can deliver over 800mA to a battery from a 5V supply at room temperature. Without a good backside thermal connection, this number could drop to less than 500mA. VCC Bypass Capacitor Many types of capacitors can be used for input bypassing; however, caution must be exercised when using multilayer ceramic capacitors. Because of the self-resonant and high Q characteristics of some types of ceramic capacitors, high voltage transients can be generated under some start-up conditions such as connecting the charger input to a live power source. Adding a 1.5Ω resistor in series with an X5R ceramic capacitor will minimize start-up voltage transients. For more information, see Application Note 88. Charge Current Soft-Start and Soft-Stop The LTC4062 includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. When a charge cycle is initiated, the charge current ramps from zero to the full-scale current over a period of approximately 100µs. Likewise, internal circuitry slowly ramps the charge current from full-scale to zero when the charger is shut off or self terminates. This has the effect of minimizing the transient current load on the power supply during start-up and charge termination. Reverse Polarity Input Voltage Protection In some applications, protection from reverse polarity on VCC is desired. If the supply voltage is high enough, a series blocking diode can be used. In other cases, where the diode voltage drop must be kept low, a P-channel MOSFET can be used (as shown in Figure 7). DRAIN-BULK DIODE OF FET LTC4062 VIN VCC 4062 F07 Figure 7. Low Loss Input Reverse Polarity Protection 4062f 16 LTC4062 U W U U APPLICATIO S I FOR ATIO USB and Wall Adapter Power Typically a wall adapter can supply more current than the 500mA limited USB port. Therefore, an N-channel MOSFET, MN1, and an extra 3.3kΩ program resistor are used to increase the charge current to 800mA when the wall adapter is present. The LTC4062 allows charging from both a wall adapter and a USB port. Figure 8 shows an example of how to combine wall adapter and USB power inputs. A P-channel MOSFET, MP1, is used to prevent back conducting into the USB port when a wall adapter is present and a Schottky diode, D1, is used to prevent USB power loss through the 1kΩ pull-down resistor. 5V WALL ADAPTER ICHG = 800mA USB POWER ICHG = 500mA D1 VCC MP1 SYSTEM LOAD BAT LTC4062 IDET C/5 + PROG Li-Ion BATTERY 3.3k 1k MN1 2k 1.24k 4062 F08 Figure 8. Combining Wall Adapter and USB Power 4062f 17 LTC4062 U TYPICAL APPLICATIO S Full-Featured Li-Ion Charger with Low-Battery Comparator (Using Time Termination) VIN 4.3V TO 8V VCC OUT BAT > 3V BAT < 3V LTC4062 1µF 1.24k 0.1µF 619Ω EN C/5 BAT TIMER PROG IDET IN+ GND 100k 800mA 715k + 347k SINGLE CELL Li-Ion BATTERY 4062 TA03 USB/Wall Adapter Power Li-Ion Charger (Using Charge Current Termination) 5V WALL ADAPTER 400mA USB POWER VCC BAT + LTC4062 1µF C/5 Li-Ion CELL PROG TIMER IDET GND 2k 2.5k 4062 TA04 4062f 18 LTC4062 U PACKAGE DESCRIPTIO DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1669) 0.675 0.05 3.50 0.05 1.65 0.05 2.15 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.38 0.05 (2 SIDES) R = 0.115 TYP 6 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 0.10 (4 SIDES) 0.38 0.10 10 1.65 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) (DD10) DFN 1103 5 0.200 REF 1 0.25 0.05 0.50 BSC 0.75 0.05 0.00 – 0.05 2.38 0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 4062f Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 19 LTC4062 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1734 Lithium-Ion Linear Battery Charger in ThinSOTTM Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed LTC1734L Lithium-Ion Linear Battery Charger in ThinSOT Low Current Version of LTC1734, 50mA ≤ ICHRG ≤ 180mA LTC4002 Switch Mode Lithium-Ion Battery Charger Standalone, 4.7V ≤ VIN ≤ 24V, 500kHz Frequency, 3 Hour Charge Termination LTC4050 Lithium-Ion Linear Battery Charger Controller Features Preset Voltages, C/10Charger Detection and Programmable Timer, Input Power Good Indication, Thermistor Interface LTC4052 Monolithic Lithium-Ion Battery Pulse Charger No Blocking Diode or External Power FET Required, ≤1.5A Charge Current LTC4053 USB Compatible Monolithic Li-Ion Battery Charger Standalone Charger with Programmable Timer, Up to 1.25A Charge Current LTC4054 Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOT Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA Charge Current LTC4057 Lithium-Ion Linear Battery Charger Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package LTC4058 Standalone 950mA Lithium-Ion Charger in DFN C/10 Charge Termination, Battery Kelvin Sensing, ±7% Charge Accuracy LTC4059 900mA Linear Lithium-Ion Battery Charger 2mm × 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output LTC4061/ LTC4061-4.4 Standalone Li-Ion Chargers with Thermistor 4.2V/4.4V, ±0.35%/±0.4% Float Voltage, Up to 1A Charge Current Interface LTC4063 Li-Ion Charger with Linear Regulator Up to 1A Charge Current, 100mA, 125mV LDO, 3mm × 3mm DFN Battery Chargers LTC4411/LTC4412 TM Low Loss PowerPath Controller in ThinSOT Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes LTC3405/LTC3405A 300mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.7V to 6V, VOUT = 0.8V, IQ = 20µA, ISD < 1µA, ThinSOT Package LTC3406/LTC3406A 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.6V, IQ = 20µA, ISD < 1µA, ThinSOT Package LTC3411 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.8V, IQ = 60µA, ISD < 1µA, MS Package LTC3440 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 2.5V, IQ = 25µA, ISD < 1µA, MS Package LTC4413 Dual Ideal Diode in DFN 2-Channel Ideal Diode ORing, Low Forward ON Resistance, Low Regulated Forward Voltage, 2.5V ≤ VIN ≤ 5.5V Power Management ThinSOT and PowerPath are trademarks of Linear Technology Corporation. 4062f 20 Linear Technology Corporation LT/TP 0205 1K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005