LM3621 Single Cell Lithium-Ion Battery Charger Controller General Description The LM3621 is a full function constant voltage, constant current (CVCC) lithium-ion (Li+) battery charger controller. It provides 1% regulation accuracy over the specified temperature range without requiring the use of external precision resistors. The IC controls five charge modes: conditioning, fast, top-off, monitor and maintenance. In addition, the LM3621 detects and flags defective batteries as well as over current and over voltage fault events. The architecture of the IC is based on high gain constant voltage and constant current control loops. The LM3621 is designed to control a switching charger, a linear charger or an off-line ac adapter charger. The LM3621 consists of a logic controller, precision bandgap reference, wide bandwidth transconductance error amplifiers, comparators, and an output buffer. The LM3621 is available in a 16-pin SOIC package and is specified over the range of 0˚C to 70˚C. Key Specifications n Tight output voltage accuracy ( ± 0.5% at TA = 25˚C) n Two selectable output voltages (4.2V or 4.1V) n Less than 1 µA current drain from fully charged battery n Preconditioning severely discharged cells (0V to 2.55V) Features Automatic end-of-charge control Preset or user adjustable charge current regulation LED drivers for charging status and fault indication Battery self-discharge refresh (maintenance) Overvoltage/overcurrent fault detection and protection Defective battery pack detection Charge current boost control for cellular phone applications n Charge interruption control input n n n n n n n Applications n Complete, full function, protected battery charger for coke or graphite anode, single cell Lithium-Ion battery packs n Linear voltage regulator controlled chargers n High efficiency switching regulator controlled chargers n Cost effective wall adapter chargers Typical Application DS100107-7 1A, 4.1V CVCC Linear Charger for Graphite Anode Lithium-Ion Battery © 1998 National Semiconductor Corporation DS100107 www.national.com LM3621 Single Cell Lithium-Ion Battery Charger Controller March 1998 Connection Diagram 16-Lead SOIC DS100107-18 Top View Order Number LM3621M or LM3621M-3.0 NSC Package Number M16A Pin Description Pin No. Symbol I/O Description 1 VBAT+ I 2 VBAT− I Battery pack low side sense input. 3 CSR I Current Sense Resistor high side input. 4 PFD O Pass FET gate Drive output. (N-channel). 5 ICOMP I Compensation pin for current regulation loop. 6 MCO O Modulation Control Output- analog control signal output 7 VCOMP I Compensation pin for voltage regulation loop. 8 ISET I 9 VSET I Charge current adjust input pin (see application section). Charge termination voltage control input (VSET = HI for 4.2V or VSET = LO for 4.1V). 10 LED1 O LED driver #1 output (open drain). 11 LED2 O LED driver #2 output (open drain). 12 ChgInt I Charge current interrupt (active LO). 13 Enable I Enable charge cycle control. 14 Boost I Maximum output current boost control (max output current increased by 80%). 15 VSS S IC common. 16 VDD S IC power supply. www.national.com Battery pack high side sense input. 2 Absolute Maximum Ratings (Note 1) Lead Temperature, soldering If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage, VDD 6.0V Power Dissipation 100 mV ESD Susceptibility (Note 2) 150˚C Storage Temperature −65˚C to +150˚C +220˚C 0˚C ≤ TA ≤ 70˚C Ambient Temperature Range 2kV Junction Temperature +215˚C Infrared (15 sec) Operating Ratings −0.3 V ≤ V ≤ VDD+0.3V All pins Vapor Phase (60 sec) 3.0V ≤ VDD ≤ 5.5V Supply Voltage Range (Note 3) Electrical Characteristics VDD = 4.2V unless otherwise specified. Specifications with standard type face are for TA = 25˚C, and those with boldface type apply over full operating temperature range. Symbol VOUT VCSR VBAT-Det VCSR-Det Parameter Battery Regulation Voltage (Note 4) Charge Current Regulation Voltage (Notes 5, 16) Battery Voltage Detection Threshold (Note 6) Charge Current Voltage Detection Threshold (Notes 7, 16) IQ Quiescent Current IOUT MCO Output Source Current VMCO Maximum MCO Output Voltage Min Typ Max Charge termination voltage for VSET = HI Conditions 4.18 4.2 4.22 V 4.24 V Charge termination voltage for VSET = LO 4.08 4.16 4.1 4.06 Units 4.12 V 4.14 V Battery conditioning (Hi-Z) charge mode, LM3621M-3.0 2.95 3.1 3.25 V Battery conditioning (Hi-Z) charge mode, LM3621M 4.05 4.1 4.15 V Monitor Mode float voltage for VSET = HI 4.05 4.09 4.13 V Monitor Mode float voltage for VSET = LO 3.80 3.85 3.90 V V Fast Charge Mode 0.475 0.5 0.525 Conditioning (Hi-Z) Charge Mode 0.04 0.05 0.06 V Boost Mode 0.855 0.9 0.945 V Overvoltage Fault Threshold for VSET = HI 4.28 4.40 4.50 V Overvoltage Fault Threshold for VSET = LO 4.18 4.30 4.40 V Battery Resistance Free Voltage Threshold 3.55 3.65 3.75 V Conditioning (Hi-Z) Charge Mode Threshold 2.45 2.55 2.40 End of charge threshold Over Current Fault Threshold Standby Mode with IOUT = 0 mA 2.65 V 2.70 V 40 0.95 VMCO = 1.0V IOUT = 1 mA, VDD = 5.5V IOUT = 1 mA, VDD = 3.0V mV 1 1.05 V 3 5 mA 20 mA 4.9 V 2.9 V GM-V V-Reg Loop Error Amp Transconductance 0.1 mA/V ISLEW-V V-Reg Loop Error Amp Slew Current 100 µA GM-I I-Reg Loop Error Amp Transconductance 1 mA/V ISLEW-I I-Reg Loop Error Amp Slew Current 200 µA THR 1 Hour Timer 55 3 60 65 min www.national.com Electrical Characteristics (Continued) VDD = 4.2V unless otherwise specified. Specifications with standard type face are for TA = 25˚C, and those with boldface type apply over full operating temperature range. Typ Max Units ILKG-0 Symbol Battery Load Current (Note 8) Parameter VDD = 0V Conditions Min 1 10 µA ILKG-MM Battery Load Current (Note 9) 1 10 µA VBSD Maximum Allowed Battery SelfDischarge(Note 10) Monitor Mode VSET = HI 70 110 150 mV VSET = LO 220 260 300 mV GCSR Fast Charge Current Regulation Adjustment Transfer Ratio (Notes 11, 12) VISET = 0.5V 0.90 0.93 0.96 V/V VLED1 = VLED2 = 1.5V ILED LED1 & LED2 Driver Sink Current VSUV Start Up Voltage (Note 13) 3.4 VUVR Under Voltage Reset (Note 14) 2.2 VPFD-MAX Maximum PFD Output Drive no DC load on PFD no DC load on PFD VPFD-MIN Minimum PFD Output Drive VIL Logic Input Low (Note 15) VIH Logic Input High (Note 15) IDIG Digital Input Leakage Current (Note 15) 20 mA V V VDD−0.2 V VSS+0.1 0.5 VDD−0.5 −1 V V V 1 µA Note 1: Absolute Maximum Ratings indicates limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device is intended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: ESD rating is based on the human body model, 100 pF discharged through 1.5 kΩ. Note 3: LM3621 requires a minimum VDD of 3.4V to start-up. After start-up, the operating range is 3.0V to 5.5V. Note 4: VOUT is measured between VBAT+ and CSR. Note 5: VCSR is measured between CSR and VSS (across the current sense resistor). Note 6: VBAT-Det is measured between VBAT+ and VBAT−. Note 7: VCSR-Det is measured between CSR and VSS (across the current sense resistor). Note 8: This is the current drawn from the battery by the LM3621 when VDD = 0V. Note 9: This is the current drawn from the battery by the LM3621 when the charger is in Monitor Mode. Note 10: This is the maximum battery voltage droop that is allowed before the charger initiates a fast charge mode to refresh the battery to its full charge capacity. Note 11: The current regulation and detection levels can be set by applying a dc voltage adjusting between 0.1V to 1V to the ISET pin without changing the value of the current sense resistor. To ensure proper operation, if the default current regulation and detection values are desired, then a capacitor of at least 100 pF should be connected from ISET to VSS (GND). Note 12: Transfer ratio of VCSR/VISET to adjust the fast charge current regulation level. See application section. Note 13: Minimum VDD supply voltage required at start-up. Note 14: The LM3621 goes to a shutdown or reset state during “brown out” (i.e., when VDD < VUVR) Note 15: Digital inputs are Enable, Boost, Chgint and VSET. To ensure proper operation, never allow any unused input pin to be left open. Note 16: No external voltage applied to Iset pin; a 100 pF capacitor is connected across Iset and VSS. Definition of Terms VOUT: Voltage measured between VBAT+ and CSR. VCSR: Charging current sense voltage measured between CSR and VSS (Gnd). RFV: The RFV (resistance free voltage, often called the float voltage) is the open circuit terminal voltage of a battery which is free from the ESR voltage drop error. VBATTERY: Battery terminal voltage measured between VBAT+ and VBAT−. ESR: The equivalent series resistance of a battery. The ESR is the purely resistive component of a battery’s impedance. Its value is usually determined by the battery construction. VISET: External voltage applied to ISET pin, measured between ISET and VSS, to override the default value of VCSR. www.national.com 4 Typical Performance Characteristics Charge Termination Voltage Change vs VDD Unless otherwise specified, TA = 25˚C) Maximum MCO Output Voltage vs VDD DS100107-10 Fast Charge Current Regulation Voltage vs VDD DS100107-17 DS100107-15 Charge Termination Voltage Regulation vs LED1 or LED2 Sink Current Fast Charge Current Regulation vs LED1 or LED2 Sink Current Charge Termination Voltage Regulation vs MCO Output Current, IOUT DS100107-20 DS100107-19 DS100107-22 Fast Charge Current Regulation vs MCO Output Current, IOUT Charger Output Voltage Current Regulation Voltage vs Battery Resistance Free Voltage DS100107-21 DS100107-14 5 www.national.com DS100107-2 FIGURE 1. LM3621 Simplified Block Diagram www.national.com 6 DS100107-3 Note 17: State 8 is not used. FIGURE 2. LM3621 Charge State Diagram 7 www.national.com DS100107-1 FIGURE 3. Typical Charge Cycle Waveform (VSET = HI) www.national.com 8 Note 19: Voltage across the current sense resistor connected between CSR and VSS. Note 18: Battery Voltage = VBAT+− VBAT, VSET = HI 9 www.national.com Fault Fault Boost Monitor Top-Off Fast Charge Fast Charge Conditioning (Hi-Z) X Yes No Yes X No Yes X Yes, Open Battery or High ESR Yes X No Yes Yes Yes, Shorted Battery or No Capacity Yes X X Yes No No No No X X No X NO Boost Mode? (Boost = HI?) Defective Pack Detected? Yes No Standby Conditioning (Hi-Z) Pack Present? (Enable = HI?) Charge Mode Input Conditions X ≥ 1V X X X X X Pulse at 0.8 Hz Pulse at 0.8 Hz Low Open Drain ≥ 1 hour X 0 > 4.09V Open Drain Pulse at 0.8 Hz < 1 hour X Low Pulse at 0.8 Hz ≥ 1hour X Low Open Drain LED1 Output Pulse at 0.8 Hz Pulse at 0.8 Hz Low Low Low Open Drain Open Drain Open Drain Open Drain Open Drain LED2 Output LED Outputs < 1hour X Timer ≥ 4.4V < 40 mV = 4.2V ≤ 40mV RFV ≤ 3.65V 0.05V < 2.55V > 40mV 0.05V < 2.55V ≥ 2.55V X X Battery Voltage (Note 18) Charge Current Detect Voltage (Note 19) TABLE 1. Truth Table for Operation of LED Drivers (LED1 and LED2) DS100107-4 FIGURE 4. General Application Circuit the reset state, the PFD (Pass FET Drive) pin is pulled low so that current is not allowed to flow into the load (e.g., Li+ battery). The LM3621 transitions from the reset state to standby mode when the conditions for a stable power source are met. Application Information Battery Charger Operation Information Figure 4 shows a general battery charger configuration using LM3621. The LM3621 provides all the necessary control functions for charging Lithium-Ion batteries precisely and safely. It features constant voltage and constant current mode operation. The on chip timer provides all critical timing functions to properly initialize the charging cycle, avoid over charging the battery above its maximum capacity level, and cut off charging to a defective battery. The LM3621 also provides the high accuracy of output voltage regulation without requiring a trim pot or precision resistors. A built-in power down switch prevents the battery from discharging through the LM3621. Digital Control Inputs The LM3621 has four digital input control pins: Enable, Boost, VSET and ChgInt. To ensure proper operation, never allow unused digital input pins to be left open circuited. Enable is used to initiate a charge cycle, Boost is used to increase the maximum regulation current output, VSET controls the maximum output voltage, and ChgInt is used to instantaneously interrupt (and resume) a charge cycle in progress. Current Boost Mode This mode is activated when the “Boost” pin is pulled high. The charger increases the maximum output current equal to a VCSR level of 0.9V. This mode of operation is overridden by a charge interrupt signal. Input Supply Voltage The voltage supply to LM3621 must never exceed 6.0V or catastrophic damage may occur to the IC. When power is first applied to the battery charger, the LM3621 will remain in a reset state until the voltage on the VDD pin exceeds 3.4V for at least one second. This ensures that the power source is stable before a charge cycle is initiated. Figure 2 shows the state diagram for the charge cycle operation. Once the LM3621 emerges from the reset state after power up, it will not go into the reset state again until the voltage on the VDD pin drops below approximately 2.2V. When the LM3621 is in www.national.com Charge Interrupt Control Charging is interrupted with the digital input “ChgInt” pulled low. The PFD pin is pulled to ground turning off the series low pass FET. This is useful to prevent charging a battery if, for example, the ambient temperature is excessively high. 10 Application Information been discharged down to as low as 0V. This is accomplished by the fact that the “ON” resistance of the low side N-channel pass FET is modulated by the PFD output. This ensures that VCSR stays constant at 50 mV regardless of what the battery voltage is, and it prevents the charger’s regulation loop from collapsing in the event that the charger’s output is shorted. The LM3621 will remain in the Hi-Z Charge mode for a maximum of one hour. If the battery voltage does not increase to at least 2.55V by the end of the one-hour interval, then PFD goes low to turn off the low side pass FET and LED1 will pulse at 0.8 Hz to indicate a defective battery. (Continued) Programmable Charge Termination Voltage The charging status for battery of graphite or coke anode is programmed with the digital input “VSET”. VSET = LO for a charge termination voltage of 4.1V, a float voltage of 3.84V and over voltage detection threshold (VBAT-Det) of 4.3V. VSET = HI for a charge termination voltage of 4.2V, float voltage of 4.09V and VBAT-Det of 4.4V. Defective Pack Detection The LM3621 automatically checks for defective battery. Whenever a defective pack is detected, the charging sequence is suspended and LED1 driver is pulsed at a rate of 0.8 Hz. A defective battery is indicated under three conditions: (1) when a battery fails to charge up to 2.55V within one hour, (2) when the battery ESR plus the contact resistance is excessive, and (3) when the pack is an open circuit. 3. Fast Charge Mode The LM3621 will transition to Fast Charge mode whenever the battery voltage is above 2.55V. During Fast Charge mode LED1 stays low and LED2 stays open drain, and the LM3621 controls the charger to behave as a current limited, constant output voltage source to the battery. If the battery voltage is less than 4.2V (for VSET = HI), the LM3621 controls the charger to behave as a constant current source. VCSR is limited to 0.5V, so the maximum charge current delivered to the battery is equal to 0.5V / RCS. Once the battery voltage reaches 4.2V, the LM3621 controls the charger to behave as a constant voltage source, and VOUT is maintained at 4.2V. As the battery continues to charge up, the charge current will decrease. Correspondingly, VCSR will decrease as well. The battery will continue to charge until VCSR has decreased to 40 mV, at which time PFD pulls low to interrupt the charge current for one second. At the end of the one second interval, the LM3621 checks to see if the battery’s Resistance Free Voltage (RFV) is greater than 3.65V or less than 3.65V. If the battery’s RFV is less than 3.65V, then the ESR of the battery is excessively high, PFD stays low to keep the charging sequence suspended and LED1 pulses at 0.8 Hz to indicate a defective battery. If the battery’s RFV is greater than 3.65V, then the LM3621 transitions to Top-Off mode. At this transition, LED1 becomes open drain and LED2 pulls low indicating a fully charged battery. Step by Step Description of a Typical Charging Sequence. (Refer to Figure 3) 1. Standby Mode The LM3621 will remain in standby while the digital inputs to the Enable and Boost pins are low. Boost overrides Enable, and Boost mode may be activated at any time with two exceptions: (1) when a deeply discharged battery (i.e., VBATTERY ≤ 2.5V) is attached to the charger or (2) when ChgInt has been activated during a normal charge cycle. Both LED drivers pull low during Boost mode. During standby, the charger’s output voltage VOUT is regulated to either 4.2V or 4.1V depending on the state of the digital input to the VSET pin (VOUT = 4.2V when VSET = high or VOUT = 4.1V when VSET = low). PFD is low so the low side pass FET is off. The LED driver pins are high impedance (open drain). Table 1 shows the state of the LED drivers during various modes of operation. 2. Charging Sequence Initialization The LM3621 determines the presence or absence of a battery pack by the state of the “Enable” pin. Enable should be pulled low when the pack is not present. When a pack is inserted into the charger, Enable should go high to initiate the charging sequence. After Enable is asserted with a battery connected to the charger, LED1 goes low and there is a one-second delay before current is allowed to flow into the battery. During this delay, the LM3621 checks the charge condition of the battery to determine if it is grossly overcharged or if it is deeply discharged. If the battery is grossly overcharged, PFD stays low keeping the low side pass FET off, and both LED drivers pulse at a frequency of 0.8 Hz to indicate a fault condition. If the battery is less than 2.55V, the LM3621 goes to the Hi-Z ( battery conditioning) charge mode. During the Hi-Z charge mode, VOUT is regulated to 4.1V, and the voltage (VCSR) across the current sense resistor (RCS) is regulated to 50 mV. The LM3621 is capable of charging a battery that has 4. Top-Off Mode During Top-Off mode, the battery is trickle charged for one hour. At the end of the one hour interval, PFD goes low to terminate charging (i.e., the charge current is interrupted), and the LM3621 transitions to Battery Monitor mode. 5. Monitor Mode During Monitor mode, VOUT drops to 4.09V (if VSET is high) or 3.84V (if VSET is low), and the battery is floating. The LM3621 typically draws less than 1 µA from the battery during Monitor mode. If the battery self discharges so that its voltage decreases to 4.09V (if VSET is high) or 3.84V (if VSET is low), then the LM3621 will transition back to Fast Charge mode to refresh the battery and charge it back up to its full capacity (Figure 2 & Figure 5). This process will continue until Enable goes low. 11 www.national.com Application Information (Continued) DS100107-5 FIGURE 5. Battery Refresh Adjustable Charge Current The current sense resistor (Rcs) converts the charging current to a voltage level, VCSR. Applying an external voltage source (VEXT) to the ISET pin will adjust the value of VCSR for Fast Charge current regulation. Simultaneously the regulation level for Boost mode, Hi-Z Charge mode, End-of-Charge threshold and over current detect threshold will also be adjusted accordingly. The voltage at ISET pin should be within the range of 1V ≥ VISET ≥ 0.1V. The transfer functions of VCSR to VISET are: Fast Charge Mode, VCSR = 0.933·VISET Hi-Z Mode, VCSR = 0.083·VISET Boost Mode, VCSR = 0.48·VISET+0.65 Over Current Threshold, VCSR = 0.36·VISET+0.79 End-Of-Charge, VCSR = 0.07·VISET Fault Protection LM3621 provides redundant fault protection for a Li-Ion battery pack. If the charger’s control loop is accidentally opened, the regulation voltage will begin to increase beyond the level that are safe for the battery. In order to protect the battery from a fault condition, PFD goes low to turn off the series pass FET whenever the voltage across the battery exceeds the over voltage detection threshold (VBAT-Det) or whenever VCSR exceeds 1V. A fault condition also causes both of the LED drivers to pulse at 0.8 Hz. Enable must go low to cause the LM3621 to transition from the Fault State to Standby mode. Low Current Drain of Battery If power is inadvertently removed from the battery charger, the voltage at the VDD pin will collapse to the same potential as the VSS pin. An internal switch will disconnect the circuitry of the LM3621 from the VBAT+ pin so that no more than 1µA (typical) of leakage current will be drawn from the battery. DS100107-16 FIGURE 6. Adjusting VCSR by applying VEXT to ISET pin www.national.com 12 Application Information (Continued) DS100107-9 FIGURE 7. Charge Current Regulation (VCSR) vs ISET Voltage DS100107-8 FIGURE 8. Charge Current Detection (VCSR) vs ISET Voltage 13 www.national.com LM3621 Single Cell Lithium-Ion Battery Charger Controller Physical Dimensions inches (millimeters) unless otherwise noted 16-Lead SOIC Package Order Number LM3621M or LM3621M-3.0 NSC Package Number M16A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 2. A critical component in any component of a life support 1. Life support devices or systems are devices or sysdevice or system whose failure to perform can be reatems which, (a) are intended for surgical implant into sonably expected to cause the failure of the life support the body, or (b) support or sustain life, and whose faildevice or system, or to affect its safety or effectiveness. ure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5620-6175 Fax: 81-3-5620-6179 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.