LTC1729 Series Li-Ion Battery Charger Termination Controllers U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®1729 series is a family of smart termination controllers for lithium-ion battery chargers. These ICs provide trickle charge preconditioning, temperature charge qualification, time or charge current termination, automatic charger and battery detection and status output. Built-In Termination: 3-Hour Time-Out C/10 Detection with Status Indicator Trickle Charge Preconditioning If Cell < 2.7V Charging Enabled When 0°C < T < 50°C Automatic Charger Present Detection Automatic Battery Present Detection 1- or 2-Cell, 4.1V/Cell or 4.2V/Cell Options Precision Internal 0.2% Voltage Feedback Divider Compatible with LT1505/LT1510/LT1511/ LT1512/LT1513/LT1769 Small Footprint/Low Profile Combining the LTC1729 series part with the LT®1510 (1.5A), LT1769 (2A), LT1511 (3A) and LT1505 (> 4A) step-down chargers is a simple operation. Connecting six pins from the LTC1729 series part to the step-down chargers completes the integration. The LTC1729 termination controllers are also compatible with step-down/ step-up (SEPIC) chargers, including the LT1512 (2A switch) and LT1513 (3A switch). U APPLICATIO S ■ ■ ■ Cellular Phones PDAs Cradle Chargers Camcorders The LTC1729 series is available in the 8-pin MSOP and SO packages. , LTC and LT are registered trademarks of Linear Technology Corporation. U ■ TYPICAL APPLICATIO MBRM120T3 MBRM120T3 1µF LT1510-5 0.22µF INPUT POWER 8.2V TO 20V VCC SW 300Ω CIN* 10µF 6.19k PROG L1** 10µH BOOST 1k VC GND MMBD914L 0.1µF OVP SENSE BAT + COUT*** 22µF + 4.2V LTC1729-4.2 1 2 200Ω 1µF 3 4 OVP BAT SENSE GND VCC VC STATUS NTC * TOKIN OR MARCON SURFACE MOUNT ** COILTRONICS TP3-100, 10µH, 2.2mm HEIGHT (0.8A CHARGING CURRENT) COILTRONICS TP1 SERIES, 10µH, 1.8mm HEIGHT (<0.5A CHARGING CURRENT) *** PANASONIC EEFCD1B220 † LUMEX SML-LX0805GW-TR 8 0.1µF 1.4k 7 D1† CHARGE STATUS 6 1729 F01 5 10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT OPTION: TIE RESISTOR TO STATUS FOR CHARGE TERMINATION AT LOW CHARGING CURRENT Figure 1. 500kHz Li-Ion Cell Phone Charger (0.8A) 1 LTC1729 Series W W W AXI U U ABSOLUTE RATI GS (Note 1) VCC ......................................................................... 30V SENSE, VBAT, NTC .................................... – 0.3V to 15V VC ............................................................. – 0.3V to 15V OVP ............................................................ – 0.3V to 5V STATUS .................................................... – 0.3V to 30V Operating Temperature Range .................... 0°C to 70°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C U U W PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW OVP BAT SENSE GND 8 7 6 5 1 2 3 4 VCC VC STATUS NTC MS8 PACKAGE 8-LEAD PLASTIC MSOP LTC1729CMS8-4.1 LTC1729CMS8-4.2 LTC1729CMS8-8.2 LTC1729CMS8-8.4 ORDER PART NUMBER TOP VIEW OVP 1 8 VCC BAT 2 7 VC SENSE 3 6 STATUS GND 4 5 NTC MS8 PART MARKING TJMAX = 150°C, θJA = 200°C/ W LTLY LTJH LTLZ LTJG LTC1729CS8-4.1 LTC1729CS8-4.2 LTC1729CS8-8.2 LTC1729CS8-8.4 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO 172941 172942 172982 172984 TJMAX = 150°C, θJA = 150°C/ W Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VIN = 8V SYMBOL PARAMETER LTC1729-4.1/LTC1729-4.2 MIN TYP MAX CONDITIONS UNITS DC CHARACTERISTICS ● 1 1.0 10 0.5 5 1.4 17 3.0 12 2.0 21 5.0 µA mA mA mA ● 5.5 6.5 7.5 V ● 5.0 6.0 7.0 V VIN = 5V (Below UVLO), VBAT = 4.2V VIN = 8V, VBAT = 4.25V No Bat VIN = 8V, VBAT = 2.5V Trickle VIN = 8V, VBAT = 3.5V Charge ● ● ● –1 40 – 19 – 2.7 – 0.1 73 – 12 – 1.3 1 120 – 9.5 – 0.5 µA µA mA mA VBAT Clamp No Bat (External 200µA Pull-Up on VBAT) ● 4.25 4.5 4.75 V VMAX High VBAT Threshold High Going Threshold Low Going Threshold ● ● 4.25 4.25 4.51 4.50 4.75 4.75 V V VMIN Low VBAT Threshold High Going Threshold Low Going Threshold ● ● 2.55 2.45 2.7 2.6 2.85 2.75 V V ISENSE SENSE Pin Current Charge State, VSENSE = 3V ● 85 100 115 µA VC10 SENSE Pin C/10 Offset Charge State, VC10 = (VBAT – VSENSE) ● ±1 ±2.5 mV ICC VCC Supply Current VLKOH VIN Undervoltage Lockout High VLKOL VIN Undervoltage Lockout Low IVBAT VBAT Current VCLAMP 2 VIN = 5V (Below UVLO) VIN = 8V, VBAT > 4.5V, No Bat VIN = 8V, VBAT = 2.5V Trickle VIN = 8V, VBAT = 3.5V Charge ● ● LTC1729 Series ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VIN = 8V SYMBOL PARAMETER CONDITIONS INTC NTC Pin Current VNTC = 1V VNTC-RESET Thermistor Pin Reset Threshold VNTC-HOT Thermistor Pin Hot Hold Threshold VNTC-COLD LTC1729-4.1/LTC1729-4.2 MIN TYP MAX UNITS ● 90 100 110 µA ● 0.160 0.206 0.240 V High Going Threshold Low Going Threshold ● ● 0.460 0.380 0.486 0.405 0.510 0.430 V V Thermistor Pin Cold Hold Threshold High Going Threshold Low Going Threshold ● ● 2.70 2.10 2.79 2.23 2.90 2.35 V V VOVP OVP Pin Voltage VBAT = 4.1V or VBAT = 4.2V ● 2.455 2.460 2.465 2.465 2.475 2.470 V V VOL-ST Output Low Voltage-STATUS Pin IO = 3mA ● 0.5 0.9 1.2 V VOL-VC Output Low Voltage-VC Pin IO = 1mA ● 0.35 0.6 0.75 V ISOFT Status Soft Pull-Down Current VSTATUS = 4.5V ● 40 50 65 µA The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VIN = 12V SYMBOL PARAMETER LTC1729-8.2/LTC1729-8.4 MIN TYP MAX CONDITIONS UNITS DC CHARACTERISTICS ● 1 1.0 10 0.5 6 1.4 17 3.0 12 2.0 21 5.0 µA mA mA mA ● 9.5 10.4 11.4 V ● 8.5 9.6 10.5 V VIN = 9V (Below UVLO), VBAT = 8.4V VIN = 12V, VBAT = 8.5V No Bat VIN = 12V, VBAT = 5V Trickle VIN = 12V, VBAT = 7V Charge ● ● ● –1 60 – 19 – 2.7 – 0.1 95 – 12 – 1.3 1 140 – 9.5 – 0.5 µA µA mA mA VBAT Clamp No Bat (External 200µA Pull-Up on VBAT) ● 8.5 9 9.5 V VMAX High VBAT Threshold High Going Threshold Low Going Threshold ● ● 8.5 8.5 9.013 9 9.5 9.5 V V VMIN Low VBAT Threshold High Going Threshold Low Going Threshold ● ● 5.1 4.9 5.4 5.2 5.7 5.5 V V ISENSE SENSE Pin Current Charge State, VSENSE = 7V ● 85 100 115 µA VC10 SENSE Pin C/10 Offset Charge State, VC10 = (VBAT – VSENSE) ● ±1 ±2.5 mV INTC NTC Pin Current VNTC = 1V ● 90 100 110 µA VNTC-RESET Thermistor Pin Reset Threshold ● 0.160 0.206 0.240 V VNTC-HOT Thermistor Pin Hot Hold Threshold High Going Threshold Low Going Threshold ● ● 0.460 0.380 0.486 0.405 0.510 0.430 V V VNTC-COLD Thermistor Pin Cold Hold Threshold High Going Threshold Low Going Threshold ● ● 2.70 2.10 2.79 2.23 2.90 2.35 V V VOVP OVP Pin Voltage VBAT = 8.2V or VBAT = 8.4V ● 2.455 2.460 2.465 2.465 2.475 2.470 V V VOL-ST Output Low Voltage-STATUS Pin IO = 3mA ● 0.5 0.9 1.2 V VOL-VC Output Low Voltage-VC Pin IO = 1mA ● 0.35 0.6 0.75 V ISOFT Status Soft Pull-Down Current VSTATUS = 4.5V ● 40 50 65 µA ICC VCC Supply Current VLKOH VIN Undervoltage Lockout High VLKOL VIN Undervoltage Lockout Low IVBAT VBAT Current VCLAMP VIN = 9V (Below UVLO) VIN = 12V, VBAT > 9V, No Bat VIN = 12V, VBAT = 5V Trickle VIN = 12V, VBAT = 7V Charge ● ● 3 LTC1729 Series ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS AC CHARACTERISTICS TIMER1 Timer for Trickle-Charge Preconditioning ● 0.869 1 1.305 Hr TIMER2 Timer for Charging ● 2.61 3 3.55 Hr TIMER3 Timer for VMAX Filter ● 0.764 0.859 1.043 sec TIMER4 Timer for VC/10 Filter ● 3.055 3.5 4.17 sec tOSC Oscillator Period ● 6.66 7.63 9.09 µs Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: VIN = 8V for LTC1729-4.1/LTC1729-4.2; VIN = 12V for LTC1729-8.2/LTC1729-8.4 U W TYPICAL PERFOR A CE CHARACTERISTICS IVBAT vs Temperature (4.2V Version) 14 IVBAT vs Temperature (8.4V Version) 14 VBAT = 2.5V IVBAT vs VCC (4.2V Version) 14 VBAT = 5V 12 12 12 10 10 10 8 6 IVBAT (mA) IVBAT (mA) IVBAT (mA) VBAT = 2.5V 8 6 8 6 4 4 4 2 2 2 0 0 0 VBAT = 3.5V 0 25 50 75 25 0 100 50 100 75 IVBAT vs VCC (8.4V Version) ICC vs VCC (4.2V Version) 8 10 12 10 8 0 2 14 18 22 VCC (V) 26 30 1729 G04 8 6 VBAT = 3.5V 4 VBAT = 7V 30 VBAT = 5V VBAT = 2.5V 6 4 26 ICC vs VCC (8.4V Version) ICC (mA) 12 ICC (mA) IVBAT (mA) 10 6 22 14 VBAT = 5V 10 18 VCC (V) 14 1729 G03 14 12 2 10 1729 G02 1729 G01 4 6 TEMPERATURE (°C) TEMPERATURE (°C) 4 VBAT = 7V 2 6 10 14 18 VCC (V) 22 26 30 1729 G05 10 14 18 22 VCC (V) 26 30 1729 G06 LTC1729 Series U U U PI FU CTIO S OVP (Pin 1): Connection to an Internal Precision Resistor Divider Used as a Voltage Feedback Monitor for ConstantVoltage Mode Charging. BAT (Pin 2): Input to Battery Monitor Circuits and OVP Resistor Divider. The battery monitor circuits activate trickle charge preconditioning, battery present detection and C/10 current detection. This pin is in a high impedance state when VCC is below the undervoltage lockout threshold. During trickle charge preconditioning and charging the BAT pin sources 12mA and 1.3mA respectively. The current sources are clamped from driving the BAT pin above 4.5V/cell with an internal pull-down transistor. In the No Bat, Done and Pause states or the Hold and Reset modes, the current sources are turned off, leaving only the 55k OVP divider as a load on the BAT pin. Most chargers have a 200µA current source that will compensate for this 50µA to 80µA load. SENSE (Pin 3): Input to C/10 Current Detection Circuit. This pin sinks 100µA during the Charge state which is used to program the C/10 current threshold. GND (Pin 4): Ground. NTC (Pin 5): Input to the NTC Thermistor Monitoring Circuits. When the voltage on this pin is above 2.79V (cold) or below 0.405V (hot), the state machine is locked in the present state and the timer is stopped. This is called the Hold mode. While in the Hold mode, the charger is turned off via the VC pin and the current sources on BAT and SENSE pins are turned off. The STATUS pin is not affected. If the NTC pin is below 0.2V, the state machine is forced in the reset mode with all the timers cleared to zero. The current sources on the BAT pin and SENSE pin are disabled leaving the 55k OVP divider. The STATUS pin is pulled low in the Reset mode. There is a 100µA current source on the NTC pin to bias the NTC thermistor. This current source is active when the VCC is greater than the undervoltage lockout threshold. STATUS (Pin 6): Open-Drain Output for C/10 Charge Termination Detection Circuit. When in the Charge state, this pin is pulled low. Once the charge current drops below the C/10 current threshold for three seconds, the pulldown transistor is disabled, and a 50µA pull-down current sink remains activated until the 1- or 3-hour time-out or the battery or wall adapter is removed. VC (Pin 7): Open-Drain Output for Turning Off the Charger. When this pin is open circuit, the charger is active. Normally this pin allows the charger to be active for three hours. VCC (Pin 8): Input Supply. For 4.1V or 4.2V single cell operation, VCC should be between 8V and 28V with the IC turning off when VCC drops below 6V. For 2-cell applications, the undervoltage lockout is 10.4V with a minimum VCC of 12V. Removing the wall adapter will trigger an undervoltage lockout and put the IC in a high impedance condition. When the supply is connected, the IC is initialized in the Reset mode with the state machine forced in the Charge state with all the timers set to zero. 5 LTC1729 Series W BLOCK DIAGRA 7 VC M2 SENSE 3 100µA UVLO 6 STATUS – M3 COMP1 + 50µA C/10 1.3mA 12mA COMP2 BAT + 2 UVLO M1 4.5V/CELL CLAMP 4.5V/CELL – 2.7V/CELL + VMAX LOGIC AND TIMER COMP3 OVP 1 2.465V – VMIN HOLD 100µA COMP4 + NTC 5 2.79V – 0.405V + COMP5 – COMP6 0.2V + RESET – 1729 F02 Figure 2. Block Diagram 6 LTC1729 Series U W U U APPLICATIO S I FOR ATIO Overview The LTC1729 is a charge termination controller for the LT1505/LT1510/LT1511/LT1512/LT1513/LT1769 constant-voltage/constant-current battery charger family. Table 1 details these chargers. The primary function of this IC is to stop the charger after three hours of constantvoltage/constant-current charging. The secondary function of this controller includes an indication when the charge current (during constant-voltage mode) drops below a user-selected threshold. A 500kHz Li-Ion cell phone charger is shown in Figure 1. The LTC1729 requires only six external components when combined with the standard LT1510 application. The LTC1729 provides a complete and tiny solution for cellular phones and other portable applications. Table 1. Battery Chargers LT1505 4A Step-Down Charger with Input Current Limit LT1510 1.5A Step-Down Charger LT1510-5 1.5A 500kHz Step-Down Charger LT1511 3A Step-Down Charger with Input Current Limit LT1512 2A Switch SEPIC Charger LT1513 3A Switch SEPIC Charger LT1769 2A Step-Down Charger with Input Current Limit Block Diagram Figure 2 shows the block diagram of the LTC1729. The IC consists of six comparators, a resistive divider, a UVLO block and a logic and timer block. Comparator COMP1 is used to indicate C/10 charge current threshold. (“C” is a term used to indicate the Amperehour capacity of a cell.) Figure 3 details the C/10 detection circuit. The resistor and capacitor on the SENSE pin filter the signal from the 0.2Ω current sense resistor R1. The 100µA current sink on the SENSE pin develops 20mV across the 200Ω resistor R2. This sets a 20mV offset on COMP1 that sense resistor R1 must equal before C/10 current is indicated. The C/10 is not recognized by the logic until it passes through a 3-second digital filter. For cases where there are multiple batteries to be charged, the LTC1729 detects when a battery is removed and resets the timers for the next charge cycle. The battery present detection is the primary function of comparator COMP2. When the battery is disconnected from the LTC1729, the voltage at the BAT pin will begin ramping upward. This is due to a current source inside the charger or an external pull-up resistor. Once the voltage on the BAT pin exceeds the 4.5V/cell limit, COMP2 signals a VMAX = true to the logic and turns on a transistor that clamps the voltage. There is the possibility of an overvoltage transient at the charging terminals. This occurs if the battery protection circuit, which is often included in the battery pack, opens the connection to the battery during high current charging (constant-current mode). This is a result of energy storage in the inductor. COMP2 senses the overvoltage and clamps the VC pin, reducing the duty cycle of the charger. If the battery protection circuit quickly returns battery connection to the charger (in less than one second), then the LTC1729 continues charging without resetting the timers. VCC CHARGING CURRENT LTC1729 IBIAS + 20mV – + 20mV – R1 0.2Ω R2 200Ω SENSE C1 1µF STATUS – COMP1 BAT CHARGE LED 100µA + 3-SEC FILTER LOGIC AND TIMERS 50µA 1729 F03 Figure 3. C/10 Detection Circuit 7 LTC1729 Series U W U U APPLICATIO S I FOR ATIO For a battery that has been deeply discharged, the LTC1729 provides a 12mA start-up current. This preconditioning trickle charge begins when the battery voltage drops below 2.7V/cell. Comparator COMP3 is used to determine when this condition exists. The battery operating range is summarized in Figure 4. With a 10k negative TC thermistor connected to the NTC pin, the LTC1729 will disable charging if the temperature is not in the 0°C to 50°C range. A thermistor must be present at this pin, or if the temperature qualification feature is not used, a 10k resistor must be used in its place. This pin should not be left open. The NTC thermistor monitoring circuits consist of COMP4, COMP5 and COMP6. The NTC pin voltage range is shown in Figure 5. Comparators COMP4 and COMP5 signal the logic when the temperature is below 0°C or above 50°C. The 100µA bias current through the 10kΩ thermistor will generate 2.79V at 0°C and 0.405V at 50°C. The voltage hysteresis on COMP4 and COMP5 is designed to give 10°C of temperature hysteresis. If the voltage on the NTC pin drops below 0.2V, the comparator COMP6 generates a reset to the logic and timer block. To provide accurate charge voltages, the internal resistor divider is trimmed to provide a precise ±0.2% voltage of 2.465V at the OVP pin for the four battery voltage options of 4.1V, 4.2V, 8.2V and 8.4V. When the input supply is removed in step-down charger designs, the VCC pin does not drop to 0V, but is held to a diode drop below the battery voltage. This is due to the internal parasitic diode from the SW pin to the VCC pin that is present in the LT1510, LT1511, LT1769, and the body diode of the top MOSFET in the LT1505 charger. Removing the input supply will result in the VCC pin dropping below the UVLO threshold, thus shutting down the LTC1729 and minimizing battery drain. Once the input supply is connected, the LTC1729 resets the timers and begins another charge cycle. There is a disconnect transistor that will remove the OVP resistor divider from the battery when the VCC voltage drops below the UVLO threshold. If external circuitry is connected directly to the VCC pin and the input power is removed, battery current will flow through the charger’s internal parasitic diode (SW pin to VCC pin), discharging the battery and possibly damaging the charger if currents greater than 1A are present. If external circuitry is used, connect it directly to the input power source (which is the anode of the input Schottky diode). The logic and timer block consists of a state machine, oscillator and counter. The state machine will be discussed in detail in the next section. The oscillator is internally trimmed to 131kHz. The counter is composed of a chain of 25 flip-flops that includes self-test circuitry. HOLD MODE BATTERY VOLTAGE VMAX = 1V VMIN = 0V BATTERY CLAMP PULL-DOWN ON 4.5V/CELL VMAX = 0V VMIN = 0V NORMAL CHARGE 2.7V/CELL VMAX = 0V VMIN = 1V NORMAL CHARGE 0.405V HOLD MODE 0.2V TRICKLE CHARGE PRECONDITIONING 1729 F04 Figure 4. BAT Voltage Operating Range 8 THERMISTOR VOLTAGE 2.79V RESET MODE 1729 F05 Figure 5. NTC Voltage Operating Range LTC1729 Series U W U U APPLICATIO S I FOR ATIO State Machine Reset and Hold are the two modes that will cause the charger to stop charging (VC pin pulled low) and ignore the state machine. The Reset mode clears all the timers and forces the state machine to begin in the Charge state (STATUS pin pulled low). This mode is only activated momentarily at power-up or when the NTC pin is below the Reset threshold. The other interrupt condition is called the Hold mode. When the voltage on the NTC pin is above 2.79V (cold) or below 0.405V (hot), the state machine is locked in the present state until the NTC pin voltage returns to the proper range. While in the Hold mode, the charging is disabled and the timers are frozen. The state machine is responsible for the following items: 1. When to start and stop the charger. The internal timer must be initialized every time a new battery is installed or when the input supply is applied. 2. When a battery is installed, the state machine must determine if it is a new battery or if the previous battery has been reinstalled. 3. When a deeply discharged battery is installed, trickle charge conditioning must take place before the full charge current. The charger is enabled only during the charger “ON” state. There are three ways that the state machine can exit the charger “ON” state. The first is for a 3-hour time-out which is denoted as the time > tMAX transition to the Done state. The state machine diagram is shown in Figure 6. Note that the Charge state includes the Precondition state, the charger “ON” state and the Reset mode. CHARGE RESET MODE IBAT = 0 STATUS = PULL-DOWN VC = PULL-DOWN VBAT < VMIN VBAT > VMIN VBAT > VMIN PRECONDITION IBAT = 12mA STATUS = PULL-DOWN V BAT < VMIN VC = PULL-DOWN t MAX = 1HR VBAT < VMAX FOR MORE THAN 1SEC CHARGER “ON” IBAT = 1.3mA STATUS = PULL-DOWN VC = OPEN t MAX = 3HR TIME > t MAX VBAT > VMAX PAUSE IBAT = 0 STATUS = PULL-DOWN VC = PULL-DOWN VBAT > VMAX FOR MORE THAN 1SEC NOTE: FOR STATUS PULL-DOWN = HARD: FOR CURRENT > C/10 PULL-DOWN = 50µA: FOR CURRENT < C/10 FOR 3SEC DONE IBAT = 0 STATUS = OPEN VC = PULL-DOWN VBAT < VMAX FOR MORE THAN 1SEC VBAT > VMAX FOR MORE THAN 1SEC NO BAT IBAT = 0 STATUS = OPEN VC = PULL-DOWN VNTC > 2.79V OR VNTC < 0.405V VNTC < 2.79V AND VNTC > 0.405V HOLD MODE IBAT = 0 STATUS = PREVIOUS STATUS VC = PULL-DOWN 1729 F06 Figure 6. State Diagram 9 LTC1729 Series U W U U APPLICATIO S I FOR ATIO Second, if the battery is removed from the charger, the VMAX signal is activated as mentioned in the Block Diagram section. This causes the state machine to make the VBAT > VMAX transition to the Pause state. The third way to exit the charger “ON” state is with a VBAT < VMIN transition to the Precondition state. The battery will need to drop below 2.6V/cell to be less than VMIN. This is not a likely scenario. Once in the Pause state, there are two ways to proceed. The first is to go to the No Bat state. This requires that the VBAT remain greater than VMAX for more than one second. From these conditions, the LTC1729 interprets that a battery has been removed. If the voltage on the BAT pin stays less than VMAX for more than one second, then the state machine returns to the Charge state (Precondition and charger “ON”). This is interpreted as a momentary open caused by the battery pack protection circuitry or loose contact. The Done state can only proceed to the No Bat state. From outside the LTC1729 this transition is undetectable. The requirement for this transition is for the BAT pin voltage to exceed VMAX for more than one second. The IC now assumes that the battery has been removed. From the No Bat state, there is only one possible transition. The No Bat state can move to the Charge state if the voltage on the BAT pin remains less than VMAX for one second. The LTC1729 will now work on the assumption that a new battery has been installed. Although the Precondition and Charger “ON” both reside in the Charge state, there are differences between these states. The main purpose of the Precondition state is to slowly bring a heavily discharged battery up to a minimum level before full charge current begins. The Precondition state uses a 12mA current source to trickle charge the battery with a 1-hour time-out transition to the Done state. The Charger “ON” state enables the external charger and the time-out is increased to three hours. For the entire time in the Precondition state, the STATUS pin uses a hard pull-down. In the Charger “ON” state the STATUS pin uses two types of pull-down: hard pull-down and soft 50µA pull-down. 10 Status Output Pin The STATUS pin is designed to provide an indication that the battery is charging. Once the current drops below the C/10 threshold, the battery is close to being fully charged. The LTC1729 turns off the hard pull-down once the C/10 comparator is active for more than three seconds. The 50µA soft pull down remains in effect until the 3-hour time-out is completed or the input power is removed. By using two different value pull-up resistors, a microprocessor can detect three states from this pin (charging, C/10 and stop charging). See Figure 7. VIN VDD 8 VCC 200k LTC1729 STATUS 6 µPROCESSOR 3k OUT IN 1729 F07 Figure 7. Microprocessor Interface When the LTC1729 is in charge mode, the STATUS pin is pulled down by an internal N-channel MOSFET. To detect this mode, force the digital output pin, OUT, high and measure the voltage at the STATUS pin. The N-channel MOSFET will pull the pin low even with a 3k pull-up resistor. Once the charge current drops to 10% of the full-scale current (C/10), the N-channel MOSFET is turned off and a 50µA current source is connected to the STATUS pin. The IN pin will then be pulled high by the 3k pull-up. By forcing the OUT pin into a high impedance state, the current source will pull the pin low through the 200k resistor. When the internal timer has expired, the STATUS pin will change to high impedance state and the 200k resistor will then pull the pin high to indicate the charging has stopped. Terminate at C/10 Current Charging can also be terminated using C/10 detection before the 3-hour time-out. By connecting the low side of the NTC thermistor to the STATUS pin instead of ground, LTC1729 Series U W U U APPLICATIO S I FOR ATIO the NTC pin will float to 5V as soon as the Status pull-down is open. This will force the state machine into the Hold mode. The VC pin is pulled low which turns off the charger. This circuit is shown in Figure 8. In order to restart the charging process for a new battery, the NTC pin will need to be momentarily brought below 0.2V or the VCC pin brought below the UVLO threshold. The automatic battery detection features are disabled during the Hold mode. Using Status as a Charging Indicator In many applications circuits shown in this data sheet, the STATUS pin is used to indicate when C/10 has occurred (charge current has dropped to 10% of the full charge current). This C/10 number is not fixed, but is set by an external resistor connected to the LTC1729 SENSE pin. A 100µA bias current through this resistor develops a voltage which is compared with the voltage across the charge current sense resistor. When these voltages are equal, the open-drain STATUS pin turns off. Connecting an LED to the STATUS pin will give a visual indication during the precondition trickle charge and the portion of the main charge before C/10 has occurred. By reducing the LTC1729 SENSE pin resistor to 0Ω, the STATUS pin function can be changed to a charging indicator (Figure 9). The LED on the STATUS pin will always go off after the 3-hour charge cycle is completed, regardless of the C/10 circuitry. LTC1729-4.2 1 OVP 2 BAT 1µF 3 200Ω SENSE 4 OVP VCC BAT SENSE VC STATUS GND NTC 8 7 VCC 0.1µF VC 6 5 10k NTC THERMISTOR NTHS1206N02 VISHAY/DALE 1729 F08 Figure 8. Terminate Charging at C/10 CHARGE CURRENT LTC1729 IBIAS + – SENSE RESISTOR SENSE – BAT + 100µA COMP1 1729 F09 Figure 9. Modify C/10 Indication to Create Charging Indicator 11 LTC1729 Series U TYPICAL APPLICATIO S Wide Input Voltage Range 1A Charger VIN 3V TO 28V L1** + C3 VIN 22µF C2* 4.7µF Si9925 D1 MBRS340 BOOST VSW + L2** ON/OFF R1 29.4k S/S LT1512 VFB GND VC C4 0.33µF R5 470Ω C5 0.1µF D2 1/2 BAT85S CAP + OSC LTC1044 GND LV C1 22µF ×2 CAP – D3 1/2 BAT85S VOUT + R4 39Ω IFB V+ 10µF R2 12.4k R3 0.1Ω R6 0.1Ω 8.4V RPULL-UP 47k LTC1729-8.4 R7 C6 100Ω 1µF + OVP VCC BAT VC C7 10µF 220k 1729 TA01 SENSE GND STATUS R8:10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT NTC R8 * TOKIN CERAMIC 1E225ZY5U-C203-F ** L1, L2 ARE TWO 10µH INDUCTORS: SUMIDA CDRH6D38-100 Using STATUS Pin to Indicate Charge Status TO VCC 12V VCC 8 0.1µF 2.2k VC 7 LTC1729 STATUS NTC 6 5 PNP: MMBT3906 12 47k 10k 2k 4.7k 2k CONDITION NO WALL ADAPTER CHARGING (IBAT > C/10) CHARGING (IBAT < C/10) TIMER EXPIRED AMBER OFF ON OFF OFF GREEN OFF OFF ON ON 1729 TA03 AMBER LED GREEN LED LTC1729 Series U TYPICAL APPLICATIO S 4A, 2-Cell Lithium-Ion Battery Charger TO SYSTEM LOAD DBODY M3 Si4435 VIN (FROM ADAPTER) RS4 0.025Ω + R7 500Ω C1 1µF CIN* 47µF 35V C4 D3 0.1µF MMSD4148 VCC BOOST BOOSTC GBIAS CLN TGATE CLP R5 3k SW INFET LT1505 SYNC SHDN VFB RPROG 4.93k 1% C2 0.68µF M1 Si4412 M2 Si4412 PROG CAP D4 MBRS140 AGND RS2 200Ω 1% R8 100Ω * SANYO OS-CON ** SUMIDA CDRH127-150 *** AVX TPSD226L025R0200 † C6 NOT NEEDED IF FLAG NOT USED †† LUMEX SML-LX0805GW-TR OVP VCC BAT VC SENSE GND + RS3 200Ω 1% RPULL-UP 10k LTC1729-8.4 C8 0.1µF COUT*** 22µF ×2 8.4V CPROG 1µF PGND BAT2 BAT SENSE SPIN + R4 3k C5 0.33µF R3 300Ω 4.1V RS1 0.025Ω L1** 15µH 4.2V COMP1 C6† 0.1µF 5Ω VC 3 CELL FLAG R1 1k C7 0.68µF D2 MMSD4148 BGATE UV R6 5.1k C3 2.2µF C9 0.1µF R9 1.4k D5†† STATUS NTC 10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT OPTION: TIE RESISTOR TO STATUS FOR CHARGE TERMINATION AT LOW CHARGING CURRENT 1729 TA02 13 LTC1729 Series U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 8 7 6 5 0.118 ± 0.004** (3.00 ± 0.102) 0.193 ± 0.006 (4.90 ± 0.15) 1 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 2 3 4 0.034 ± 0.004 (0.86 ± 0.102) 0° – 6° TYP 0.021 ± 0.006 (0.53 ± 0.015) SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC 0.006 ± 0.004 (0.15 ± 0.102) MSOP (MS8) 1098 * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 14 LTC1729 Series U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC 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. SO8 1298 15 LTC1729 Series U TYPICAL APPLICATIO 3A (LT1511) Or 2A (LT1769), 2-Cell Lithium-Ion Battery Charger D1 SS24 R1 510Ω GND RS4 0.05Ω 1µF CLN SW D4 SS24 C2 0.47µF VCC LT1511 OR LT1769 C1* 15µF D2 SS24 BOOST L1** 22µH INPUT POWER 11.5V TO 28V CLP D3 MBR0540T UV R6 5.1K COMP1 C3 220pF PROG VC SPIN OVP SENSE RS2 200Ω 1% C4 0.33µF BAT R2 1k RS3 200Ω 1% RS1 0.05Ω + LTC1729-8.4 R4 100Ω R5 3k TO MAIN SYSTEM LOAD C5 1µF OVP VCC BAT VC SENSE GND C7*** 22µF CPROG 1µF R3 300Ω RPROG 4.93k + 8.4V C6 0.1µF R7 1.4k D5† STATUS NTC * TOKIN C55Y5U1E156Z ** SUMIDA CDRH125-220MC *** AVX TPSD226K025R0200 † LUMEX SML-LX0805GW-TR D1, D2, D4: GENERAL SEMICONDUCTOR 10k NTC THERMISTOR, NTHS1206N02 VISHAY/DALE NOTE: EITHER A THERMISTOR OR 10k RESISTOR MUST BE PRESENT OPTION: TIE RESISTOR TO STATUS FOR CHARGE TERMINATION AT LOW CHARGING CURRENT 1729 TA04 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1505 High Efficiency Constant-Voltage/Constant-Current Battery Charger Uses External Synchronous N-Channel FETs LT1510 Constant-Voltage/Constant-Current Battery charger Up to 1.5A Charge Current for Lithium-Ion, NiCd and NiMH Batteries, Internal RSENSE LT1511 3A Constant-Voltage/Constant-Current Battery Charger Charges Lithium, NiCd and NiMH Batteries LT1512 SEPIC Battery Charger VIN Can Be Higher or Lower Than Battery Voltage, 2A Switch LT1513 SEPIC Battery Charger VIN Can Be Higher or Lower Than Battery Voltage, 3A Switch LT1571-1/LT1571-2 LT1571-5 200kHz/500kHz Constant-Current/Constant-Voltage Battery Charger Family Up to 1.5A Charge Current for 1- or 2-Cell Li-Ion Batteries, Preset and Adjustable Battery Voltages, C/10 Charge Detection LTC1731 Linear Charger Programmable Timer, C/10 Flag, 8-Pin MSOP LTC1732 Linear Charger Programmable Timer, C/10 Flag, AC Power Good, 10-Pin MSOP LTC1759 SMBus-Controlled Smart Battery Charger LT1505 Charger Functionality with SMBus Control LT1769 2A Constant-Voltage/Constant-Current Battery Charger 28-Pin SSOP Package 16 Linear Technology Corporation 1729f LT/LCG 0800 4K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1999