SS6821

SS6821 Single-Cell Lithium-Ion Battery Protection IC FEATURES Reduction in board size with miniature SOT-23-5 package and few external components. Ultra-low quiescent current of 7µA (VCC=3.5V). Ultra-low power-down current of 0.6 µ A (VCC=2.2V). Precision over-charge protection voltage 4.35V ± 50mV for the SS6821A 4.30V ± 50mV for the SS6821B 4.25V ± 50mV for the SS6821C 4.20V ± 50mV for the SS6821D Built-in delay-time circuits for over-charge, overdischarge, and over-current protection. Load detection function during overcharge mode. Two detection levels for over-current protection. DESCRIPTION The SS6821 battery protection IC is designed to protect a lithium-ion battery from damage or reduced lifetime due to over-charge, over-discharge, and/or over-current in single-cell lithium-ion battery powered systems, such as cellular phones. The ultra-small package and few external components make the SS6821 ideal for integration into the limited space of of a battery pack. The accurate ±50mV over-charging detection voltage ensures safe and full-utilization charging. Four different specification values for over-charge protection voltage are provided for various protection requirements. The very low standby current drains little current from the cell while in storage. APPLICATIONS Protection IC for single-cell Lithium-Ion battery packs. TYPICAL APPLICATION CIRCUIT FUSE BATT+ R1 BATTERY 100 C1 0.1µF 5 VCC CS 4 2 3 GND OD OC 1 R3 R2 100K M1 SSM9926 SS6821 10M BATTM2 SSM9926 Protection Circuit for Single-Cell Lithium-Ion Battery 12/6/2004 Rev.2.02 www.SiliconStandard.com 1 of 10 SS6821 ORDERING INFORMATION SS6821-XCXXX Packing: TR: Tape and reel SOT-2 3- 5 TOP VIEW VCC 5 CS 4 PIN CONFIGURATION Package type V: SOT-23-5 Overcharge protection: A: 4.35V B: 4.30V C: 4.25V D: 4.20V Example: SS6821-A CVTR à 4.35V version, in SOT-23-5 package shipped in tape and reel 1 OC 2 GND 3 OD ABSOLUTE MAXIMUM RATINGS Supply Voltage ....................................………………….................................................... 18V DC Voltage Applied on other Pins ...............………………………….............................. 18V Charger Voltage ..............……………………….……………………................................ 14V Operating Temperature Range .....................................……………….............. -40°C~85°C Storage Temperature Range .........................…………………..................... - 65°C~125°C TEST CIRCUIT ICC R1 VCC 100 C1 0.1µF 2 VOD 3 GND OD OC 1 R3 10M VOC 5 VCC CS 4 R2 VCS 100K SS6821 12/6/2004 Rev.2.02 www.SiliconStandard.com 2 of 10 SS6821 ELECTRICAL CHARACTERISTICS PARAMETER Supply Current Power-Down Current Over-charge Protection Voltage (Ta=25°C, unless otherwise specified.) MIN. TYP. 7 0.6 4.30 4.25 VOCP 4.20 4.15 VHYS 230 4.35 4.30 4.25 4.20 300 TEST CONDITIONS SYMBOL VCC=3.5V V CC=2.2V, SS6821A SS6821B SS6821C SS6821D ICC I PD MAX. 11 1.0 4.40 4.35 UNIT µA µA V 4.30 4.25 370 mV Over-charge Hysteresis Voltage Over-discharge Protection Voltage Over-discharge Release Voltage Over-current Protection Voltage Over-charge Delay Time VCC=3.5V VCC=VOCP-0.1→ VOCP + 0.1V Over-discharge Delay Time Over-current Delay Time (1) VCC= 2.6V → 2.2V VCC=3.5V, 1V>VCS>0.2V VCC=3.5V, VCS>1V VODP 2.25 2.4 2.55 V VODR 2.85 3.0 3.15 V VOIP 180 200 220 mV TOC 100 150 200 ms TOD TOI1 6 6 12 12 18 18 50 ms ms µs V Over-current Delay Time (2) OD Pin Output “H” Voltage OD Pin Output “L” Voltage Load Detection Threshold Voltage Charge Detection Threshold Voltage TOI2 VDH VDL VCC-0.2 VCC-0.02 0.01 0.3 0.1 0.4 V V VCC=VOCP – 50mV VLD VCC=2.4V VCH -0.45 -0.3 V 12/6/2004 Rev.2.02 www.SiliconStandard.com 3 of 10 SS6821 TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs. Supply Voltage 8.0 10 Supply Current vs. Temperature Vcc=3.5V Ta=25°C 9 Supply Current (µA) Supply Current (µA) 7.6 8 7.2 7 6.8 6 6.4 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 5 -40 -20 0 Supply Voltage (V) Temperature ( °C) 20 40 60 80 Power-Down Current vs. Temperature 0.66 Overcharge Protection Voltage vs. Temperature 4.36 Vcc=2.2V Power-Down Current (µA) 0.63 Overcharge Protection Voltage (V) 4.34 SS6821B 4.32 0.60 4.30 4.28 0.57 4.26 0.54 -40 -20 0 20 40 60 80 4.24 -40 -20 0 20 40 60 80 Temperature (°C) Overdischarge Protection Voltage vs. Temperature Overdischarge Protection Voltage (V) 2.42 202 Temperature (°C) Overcurrent Protection Voltage vs. Temperature Overcurrent Protection Voltage (mV) Vcc=3.5V 201 2.41 2.40 200 2.39 199 2.38 -40 -20 0 20 40 60 80 198 -40 -20 0 Temperature (°C) Temperature ( °C) 20 40 60 80 12/6/2004 Rev.2.02 www.SiliconStandard.com 4 of 10 SS6821 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Overcharge Release Voltage vs. Temperature 4.10 3.10 Overdischarge Release Voltage vs. Temperature Overdischarge Release Voltage (V) 80 Overcharge Release Voltage (V) SS6821B 4.05 3.05 4.00 3.00 3.95 2.95 3.90 40 - -20 0 20 40 60 Temperature ( °C) 2.90 -40 -20 0 20 40 60 80 Temperature ( °C) Overcharge Delay Time vs. Temperature 145 12 Overdischarge Delay Time vs. Temperature Overdischarge Delay Time (mS) Overcharge Delay Time (mS) 140 11 135 10 130 9 125 -40 -20 0 20 40 60 80 8 -40 -20 0 20 40 60 80 Temperature (°C) Temperature (°C) Overcurrent Delay Time 1 vs. Temperature 12 Overcurrent Delay Time 1(mS) Vcc=3.5V 11 10 9 8 -40 -20 0 20 40 60 80 Temperature (°C) 12/6/2004 Rev.2.02 www.SiliconStandard.com 5 of 10 SS6821 BLOCK DIAGRAM Wake-up Control -0.3V Enable Load Detected CS 4 0.2V 0.3V Enable Overcurrent Delay Circuit 3 VCC 5 1V OD Overdischarge Delay Circuit Power-down Control Overcharge Delay Circuit 1.2V GND 2 1 OC PIN DESCRIPTIONS PIN 1: OC - PMOS open drain output for control of the charge control MOSFET M2. In normal mode, this PMOS turns on to pull the gate of the MOSFET M2 high, and the MOSFET M2 turns on. When over-charge occurs, this PMOS turns off, no current flows through R3 and the MOSFET M2 turns off. MOSFET M1 and discharging is halted. PIN 4: CS - Input pin for current sensing. Using the sum of the drain-source voltages of the MOSFET M1 and the MOSFET M2 (voltage between CS and GND), it senses the discharge current during normal mode and detects whether charging current is present during the powerdown mode. It is also used to detect whether the load is connected during over-charge mode. PIN 2: GND - Ground pin. This pin is to be connected to the negative terminal of the battery cell. PIN 3: OD - Output pin for control of discharge control MOSFET When over-discharge occurs, pin goes low to turn off the M1. this the PIN 5: VCC - Power supply pin. This pin is to be connected to the positive terminal of the battery cell. 12/6/2004 Rev.2.02 www.SiliconStandard.com 6 of 10 SS6821 APPLICATION INFORMATION turning off of the discharge control MOSFET M1. OPERATION Over-charge Protection When the voltage of the battery cell exceeds the overcharge protection voltage (VOCP) for longer than the overcharge delay time (TOC) period, charging is halted by turning off the charge control MOSFET M2. The overcharge delay time is fixed to 100ms by circuitry internal to the IC. The over-charge condition is released in one of two ways: 1. The voltage of the battery cell becomes lower than the over-charge release voltage (VOCR or VOCP- VHYS) through self-discharge. 2. The voltage of the battery cell falls below the over-charge protection voltage (VOCP) because a load has been connected. When the battery voltage is above VOCP, the over-charge condition is never released even if a load is connected to the pack. The over-current condition returns to the normal mode when the load is released and the impedance between the BATT+ and BATTterminals is 1MΩ or higher. The SS6821 is provided with two overcurrent detection levels (0.2V and 1V) and two over-current level. delay times (TOI1 and TOI2) corresponding to each over-current detection Load detection after overcharge The load detection function after over-charge is implemented by detecting the CS pin voltage. Once a load is connected to the battery pack after an over-charge, discharge current flows through the parasitic diode of MOSFET M2 and there is a diode voltage drop between CS and GND. A load is determined to be connected to the pack if the CS pin voltage is above the load detection threshold voltage (VLD). Over-discharge protection When the voltage of the battery cell goes below the over-discharge protection voltage (VODP) for longer than the over-discharge delay time (TOD) period, discharging is halted by turning off the discharge control MOSFET M1. The over-discharge delay time defaults to 10ms. Discharging is immediately resumed when the voltage of the battery cell becomes higher than over-discharge release voltage (VODR) through charging. Power-down after over-discharge When an over-discharge occurs, the SS6821 will go into power-down mode, turning off all the timing generation and detection circuitry to reduce the quiescent current to 0.6µA (VCC=2.2V). At the same time, the CS pin is pulled high to VCC through a high resistance resistor. Charge detection after over-discharge When over-discharge occurs, the discharge control MOSFET M1 turns off and discharging is halted. However, charging is still permitted through the parasitic diode of M1. Once the charger is connected to the battery pack, the SS6821 immediately turns on all the timing generation and detection circuitry. Charging is determined to be in progress if the voltage between CS and GND is below the charge detection threshold voltage (VCH). . Over-current protection In normal mode, the SS6821 continuously monitors the discharge current by sensing the voltage of the CS pin. If the voltage of the CS pin exceeds the over-current protection voltage (VOIP) for longer than the over-current delay time (TOI) period, the over-current protection circuit operates and discharging is halted by 12/6/2004 Rev.2.02 www.SiliconStandard.com 7 of 10 SS6821 DESIGN GUIDE Selection of external control MOSFETs Because the over-current protection voltage is pre-set, the threshold current for over-current detection is determined by the on-resistance of the discharge control MOSFET M1. The required on-resistance of the external control MOSFETs can be determined by the equation: RON=VOIP/ (2 x IT) (IT is the over-current threshold current). For example, if the overcurrent threshold current IT is designed to be 3A, the on-resistance of the external control MOSFETs must be 33mΩ. Users should be aware that on-resistance of the MOSFET changes with temperature variation due to heat dissipation. It changes with the voltage between gate and source as well. (Onresistance of a MOSFET increases as the voltage between gate and source decreases). Once the on-resistance of the external MOSFET changes, the over-current threshold current will change accordingly. Suppressing the ripple and disturbance from the charger To suppress the ripple and disturbance from the charger, connecting R1, C1 to the VCC pin is recommended. Protection at CS pin R2 is used for latch-up protection when the charger is connected under an over-discharge condition, and over-stress protection for accidental reverse-connection of the charger. A larger value of R2 reduces the charger leakage current in over-charge mode, but may possibly disable the charge detection function after overdischarge. A resistance value of 100KΩ is recommended. 12/6/2004 Rev.2.02 www.SiliconStandard.com 8 of 10 SS6821 TIMING DIAGRAMS l Over-charge and over-discharge protection TOC TOC VCC VOCP VOCP-VHYS VODR VODP TOD VOC VCC Hi-Z Hi-Z VOD VCC 0V charger connected load connected charger connected load connected charger connected l Over-current protection (VCC=3.5V) VCC 1V VBATT0.2V 0V TOI1