Si9731 Vishay Siliconix mP Controlled Battery Charger For 1-Cell Li-ion or 1-Cell to 3-Cell NiCd/NiMH Batteries FEATURES D Complete Isolation from Battery to External Power Supply In Shutdown D Thermal Shutdown D Minimum Number 0f External Components D ESD Protection to 4 kV on Charger Input and Battery Output D TSSOP-16 Package (1.2-mm maximum height) D Pulse Charges 1-Cell Li-ion or 1-Cell to 3-Cell NiCd/NiMH Batteries D Integrated MOSFETs With Bi-directional Reverse Current Blocking in “OFF” Mode D PWM Controlled Fast Charging Mode D Low Current Trickle Charge Mode D Pin Selectable 4.1 V or 4.2 V Charge Termination for Li-ion D Constant Voltage (CV) Termination For Li-ion D Input Over-Voltage Detector with Automatic Shutdown D External Shutdown D Under 1-mA Reverse Battery Leakage Current In Shutdown APPLICATIONS D Cellular Phone Battery Charger D Personal Digital Assistants DESCRIPTION Si9731 is a chemistry independent battery charger designed to pulse charge 1-cell to 3-cell NiCd/NiMH or 1-cell Li-ion batteries. Battery charging is accomplished under direct control from the system processor. An internal low rDS(on) MOSFET can be pulsed on and off at varying duty cycle by the system processor to pulse charge the battery at high charge current while minimizing heat dissipation. Provision is also made to trickle charge a discharged battery until the battery is charged to a high enough voltage to wake up the processor so that the processor can take control of the charging process. For charging Li-ion batteries, Si9731 includes a precision voltage reference and an error amplifier for constant voltage (CV) charge mode. FUNCTIONAL BLOCK DIAGRAM VBAT VCHARGER ON/OFF Fast Charge Trickle Charge B a t t e r y TRICKLECHARGEENABLE CVMODE Charge Control 4.1/4.2 V_TAP FAST CHARGE GND Document Number: 71321 S-02258—Rev. A, 28-Sep-00 www.vishay.com 1 Si9731 Vishay Siliconix ABSOLUTE MAXIMUM RATINGS Voltages Referenced to GND = 0 V Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65 to 150_C VCHARGER, V(CVMODE), V(TRICKLECHARGEEN), V(MAINCHARGEREN), V(ON/OFF), V(4.1 V_TAP), V(VBAT+), V(CHARGERPOWER_ON), V(CHARGERPRESENT), V(TRICKLE_VBAT) Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150_C V(CHARGERPRESENTIN), V(CHARGERPOWER_ONIN) . . . . . . . . . –0.3 V to +13.5 V Maximum Input Current (ICHARGER(max)) . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 A Maximum Sink Current CHARGERPOWER_ON and CHARGERPRESENT Pins . . . . . . . . . . . 5 mA Power Dissipation (Package)a 16-Pin TSSOP (Q Suffix)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25 W Thermal Impedance (QJA) 16-Pin TSSOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100_C/W Notes a. Device mounted with all leads soldered or welded to PC board. b. Derate 10 mW/_C above 25_C. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. RECOMMENDED OPERATING RANGE Voltages Referenced to GND = 0 V VCHARGER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 V to 12 V Ambient Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40_C to +85_C VREFBypass Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1 mF COUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 mF CIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 mF See application drawing Figure 1. SPECIFICATIONS Test Conditions Unless Specified Parameter External Charger Voltage Under Voltage Lockout on Charger UVLO Hysteresis Symbol –40_C t TA t +85_C 3.0 V v VCHARGER v 6.5 V, VON/OFF = 1.5 V Mina Rising Edge of Battery Charger 2.45 VCHARGER VUVLO VTERM+ Regulated Output Voltage 4.1 V_TAP Open Battery Over Voltage Protection VOVP Battery Over Voltage Hysteresis VOVP_HYS Battery Minimum Operating Voltage VBAT(min) Charger Voltage to Battery Voltage Comparator Offset VOS_CB Maxa 2.6 2.75 3.0 UVLOHYST Regulated Output Voltage 4.1 V_TAP to VBAT Typb VCHARGER = 5.0 V IBAT+ = 1 mA MAINCHARGEREN = 5.0 V CVMODE = 5.0 V 12 70 90 110 –10_C t TA t +40_C 4.050 4.1 4.150 –40_C t TA t +85_C 4.025 4.1 4.150 –10_C t TA t +40_C 4.150 4.2 4.250 –40_C t TA t +85_C 4.125 4.2 4.250 4.70 4.95 5.15 Rising Edge of VBAT+ Comparator Offset Voltage, VCHARGER – VBAT+ 3.32 3.41 3.50 MAINCHARGEEN— High –0.08 –0.04 –0.01 MAINCHARGEEN— Low 0.01 0.04 0.08 Charger Voltage to Battery Voltage Comparator Hysteresis V mV V 0.11 Rising Edge, VBAT+ Latch Unit 0.07 Quiescent Current (Normal Mode) IIN(VCHARGER Pin) ON-Mode 1 mA v IBAT+ v 600 mA 1 3 mA Quiescent Current (Shutdown Mode) IIN(VCHARGER Pin) OFF-Mode VON/OFF = 0 V, VCHARGER = 4.5 V 0.1 1 mA RFB1 Pin 12 to Pin 14 1 RFB2 + RFB3 Pin 12 to GND 41 Feedback Resistor Battery Leakage Current www.vishay.com 2 IPIN13 + IPIN14 VBAT+ = 4.2 V kW W VON/OFF = 0 V –1 0.1 1 VCHARGER = 0V –1 0.1 2 mA Document Number: 71321 S-02258—Rev. A, 28-Sep-00 Si9731 Vishay Siliconix SPECIFICATIONS Test Conditions Unless Specified Symbol –40_C t TA t +85_C 3.0 V v VCHARGER v 6.5 V, VON/OFF = 1.5 V Q1 ON Resistance Q1 rDS(on) MAINCHARGEREN w 1.5 V Q2 ON Resistance Q2 rDS(on) Parameter Q5 ON Resistancec Q5 rDS(on) Over Voltage Detect Threshold VCHARGER(OVD) Over Voltage Detect Threshold Hysteresis VCHARGER(OVD) CHARGERPRESENT and CHARGERPOWER_ON CHARGERPRESENTIN, CHARGERPOWER_ONIN, TRICKLECHARGEEN, MAINCHARGEEN or CVMODE VCHARGER = 4.5 V Mina Typb TRICKLECHARGEEN v 0.4 V 6 CVMODE w 1.5 V 6 Rising Edge of Battery Charger 12.2 12.8 IOH VOH = 6.5 V Output Low Voltage VOL IOL = 1 mA Logic Low Voltage VIL Logic High Voltage VIH Pull Down Current IP/D 0.7 TS/D 130 THYST 10 Thermal Shutdown Hysteresisc Shutdown High Voltage Logic Level VON/OFF(high) Shutdown Low Voltage Logic Level VON/OFF(low) Shutdown Hysteresis VON/OFF(hyst) Unit 400 mW 10 0.1 W 13.4 V 0.4 _HYS Output High Leakage Current Thermal Shutdown Temperaturec Maxa 2 mA 0.4 0.4 V 10 mA 1.5 _ _C 1.5 0.3 100 V mV Notes a. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum, is used in this data sheet. b. Typical values are for DESIGN AID ONLY, not guaranteed or subject to production testing. c. Guaranteed by design and characterization, not subject to production testing. Document Number: 71321 S-02258—Rev. A, 28-Sep-00 www.vishay.com 3 Si9731 Vishay Siliconix PIN CONFIGURATION TSSOP-16 CHARGERPRESENT = (XCHARGERPRESENT) CHARGERPRESENTIN 1 16 CHARGERPOWER_ONIN 2 15 CHARGERPOWER_ON = (XCHARGERPOWER_ON) 14 VBAT+ VCHARGER 3 ON/OFF 4 13 TRICKLE_VBAT TRICKLECHARGEEN 5 12 4.1 V_TAP CVMODE 6 11 GND MAINCHARGEEN 7 10 (N/C) (N/C) 8 9 VREF Si9731DQ Top View Ordering Information Part Number Temperature Range Package Si9731DQ –40 to 85_C Tape and Reel Eval Kit Temperature Range Board Type Si9731DB –40 to 85_C Surface Mount PIN DESCRIPTION Pin Number 1 CHARGERPRESENTIN 2 CHARGERPOWER_ONIN 3 VCHARGER 4 ON/OFF 5 TRICKLECHARGEEN 6 CVMODE 7 MAINCHARGEEN Function Logic input for CHARGERPRESENT output Logic input for CHARGERPOWER_ON output External charger Master shutdown pin. Taking ON/OFF low shuts down the charger and quiescent current drops to under 1 mA Taking this pin high disables trickle (slow) charging A logic high enables the error amplifier to linearly drive the gate of MOSFET Q1 when MAINCHARGEREN is high. An external PWM signal at MAINCHARGEREN pin controls the ON/OFF duty cycle of the Fast Charge MOSFET, Q1. 8, 10 N/C Do not connect external circuitry to this pin. Circuitry internal to the IC is connected to this pin. 9 VREF Internal 1.30-V precision bandgap reference voltage. Do not apply loads to this pin. 11 GND Low impedance system ground 12 4.1 V_TAP Connect this pin to VBAT+ for 4.1-V charge termination in constant voltage mode 13 TRICKLE_VBAT Resistor connected between this pin and VBAT to limit the trickle charge current. 14 VBAT+ 15 CHARGERPOWER_ON Open drain logic output 16 CHARGERPRESENT Open drain logic output www.vishay.com 4 Name Charger output connected to battery’s positive terminal Document Number: 71321 S-02258—Rev. A, 28-Sep-00 Si9731 Vishay Siliconix TABLE 1: BATTERY CHARGING CONTROL LOGIC (NOMINAL VOLTAGE VALUES) TRICKLE CHARGEEN CVMODE MAIN CHARGEEN ON/OFF Q1b Q2 Not Present X X X X OFF OFF Not Charging Not Present OK to Chargea X X X X OFF OFF Not Charging Over Voltage VCHARGER u12.8 V X X X X OFF OFF Not Charging VCHARGER Present OK to Chargea Mode X X X LOW OFF OFF Not Charging (Shutdown) LOW LOW LOW HIGH OFF ON Trickle Charge HIGH LOW LOW HIGH OFF OFF Not Charging (Current pulse off during Constant Current Charge) LOW LOW HIGH HIGH ON OFF HIGH LOW HIGH HIGH ON OFF LOW HIGH LOW HIGH OFF OFF HIGH HIGH LOW HIGH OFF OFF LOW HIGH HIGH HIGH ON OFF HIGH HIGH HIGH HIGH ON OFF Constant Current Charge (current pulse on) Not Charging (Current pulse off during Constant Current Charge with output limited to 4.1 V/4.2 V or end of charge in Li-Ion charging) Constant Current Charge (Output Limited to 4.1 V/4.2 V or Constant Voltage Charge) Notes a. “OK to Charge” is a flag signal that is enabled by satisfying all the following conditions: 1. Battery voltage is below 5 V 2. Charger voltage is greater than 3 V but below 12.8 V 3. If MAINCHARGEEN = Logic Low, VCHARGER > VBAT + 40 mV, If MAINCHARGEEN = Logic High, VCHARGER > VBAT – 40 mV 4. ON/OFF pin is at logic high. b. Q1 drive is determined by the error amplifier during constant voltage mode. Q1 drive is a combination of Q1 drive (digital) and the output of the error amplifier using the analog adder. The combinations are: TABLE 2 Document Number: 71321 S-02258—Rev. A, 28-Sep-00 Q1 Drive (Digital) Output of Error Amplifier Q1 Drive LOW LOW LOW (fully off) Intermediate (linear mode) LOW Intermediate HIGH LOW HIGH (fully on) HIGH HIGH Should Never Happen www.vishay.com 5 Si9731 Vishay Siliconix TYPICAL CHARACTERISTICS (25_C UNLESS NOTED) VBAT (CV Mode) vs. Temperature VBAT (CV Mode) vs. VCHARGER 4.22 4.22 4.1 TAP Open 4.1 TAP Open 4.20 4.20 4.18 V BAT – (V) V BAT – (V) 4.18 4.16 4.14 4.16 4.14 4.12 4.12 4.1 TAP to VBAT 4.10 4.1 TAP to VBAT 4.10 4.08 4.08 3 6 9 4.06 –40 12 –15 10 VCHARGER (V) Charger UVLO Rising vs. Temperature 1.0 85 VBAT Leakage vs. Temperature VCHARGER = 0 V VBAT = 4.2 V 2.70 0.8 Current V BAT – (V) V CHARGER – (V) 60 Temperature (_C) 2.75 2.65 2.60 0.6 0.4 2.55 0.2 2.50 2.45 –40 –15 10 35 Temperature (_C) www.vishay.com 6 35 60 85 0.0 –40 –20 0 20 40 60 80 100 Temperature (_C) Document Number: 71321 S-02258—Rev. A, 28-Sep-00 Si9731 Vishay Siliconix BLOCK DIAGRAM AND TYPICAL APPLICATION CIRCUIT 16 CHARGERPRESENTIN 1 Q3 15 CHARGERPOWER_ONIN CHARGERPRESENT 2 CHARGERPOWER_ON Q4 Latch ON/OFF 4 1 MW 100 kW Battery Min Voltage VCHARGER – UVL 3 + 2.6 V 3.4 V + Circuit Power – 14 + CIN 2.2 mfd OVP OK to Charge (OTC) – 12.8 V VBAT+ VBAT 5V – COUT 2.2 mfd Battery Over Voltage + B a t t e r y 56 W + – 13 Q2 Trickle_VBAT Trickle Charge Q1 Fast Charge RFB1 12 TRICKLECHARGEEN 4.1 V_TAP RFB2 5 RFB3 CVMODE 6 Digital + Q5 11 Enable MAINCHARGEEN GND 7 Voltage Generator 2.6 V 3.4 V 5V 12.8 V Temp OK – Analog Temp Sensor 9 + VREF E/A Ref Voltage 8 N/C 0.1 mfd 1.3 V 10 N/C FIGURE 1. Document Number: 71321 S-02258—Rev. A, 28-Sep-00 www.vishay.com 7 Si9731 Vishay Siliconix DETAIL OPERATIONAL DESCRIPTION Si9731 is a chemistry independent battery charger designed for use with a system processor. For example, Si9731 can be integrated within a cellular phone whereby the fast charge and trickle (slow) charge modes can be software controlled by the DSP. The device is designed to charge 1-cell Li-ion or 1-cell to 3-cell NiCd/NiMH batteries. A regulated or unregulated external dc power source such as a wall adapter rated at typically 4.5 V to 12 V is connected to Si9731’s VCHARGER input pin. Note that a typical low cost wall adaptor is comprised of a transformer, bridge rectifier and a reservoir capacitor. The wall adaptor’s output voltage decreases linearly with increase in output current. When Si9731 is fast charging the battery, the wall adaptor’s output voltage tracks the battery voltage plus the voltage drop across Q1 (charging current times MOSFET Q1’s rDS(on), see Figure 1). The key features of Si9731 are described below. Since the under voltage lock out (UVLO) point of Si9731 is 2.6 V (typical) , it is essential to keep the charger voltage above this level under all conditions, especially for fast charging of single cell NiCd/NiMH. One simple solution is adding a external resistor between VBAT+ pin and the battery, which creates extra voltage drop to elevate the charger voltage. The value of the resistor is affected by the output V-I characteristic of the ac charger. Trickle Charge The charge path is via n-channel MOSFETs Q1 or Q2 (see applications circuit of Figure 1). Si9731 defaults to trickle (slow) charge mode if the battery voltage is too low to power the main processor. With the main processor unable to drive the MAINCHARGEEN pin as well as the TRICKLECHARGEEN pins, Q1 is turned “OFF” preventing fast charging. Meanwhile n-channel MOSFET Q2 turns “ON” and establishes a trickle charge path from the external power source VCHARGER to the battery. The trickle charge current is set by an external current limiting resistor, Rext, and is approximately ITRICKLE = (VCHARGER - VBAT+)/Rext. Once the battery voltage charges up to minimum battery operating voltage 3.4 V, the internal latch is triggered and the CHARGERPOWER_ON output changes state to wake up the processor. The processor is now able to disable trickle charge mode by taking the TRICKLECHARGEEN pin high while taking control of fast charging via the MAINCHARGEEN pin. www.vishay.com 8 Fast Charge Fast charging is accomplished by the low “ON” resistance MOSFET, Q1. The application microprocessor is able to “Pulse Charge” the battery via the MAINCHARGEREN control input of Si9731. The processor monitors the battery voltage via the system A/D converter and varies the pulse charging duty cycle accordingly to maintain fast charging. Note that even though charging current may be sufficiently high, pulse charging with short “ON” time and long “OFF” time ensures that heat generation due to thermal heating is reduced. In the case of NiCd or NiMH batteries, one of several charge termination schemes may be used to terminate charge. For example, the processor may disable fast charging by sensing DV or dV/dt at the VBAT+ output or by monitoring the temperature differential DT of the battery. Following fast charge, trickle charge may be enabled to “top off” the battery. When charging a 1-cell Li-ion battery, fast charging will operate in two modes, constant current mode followed by constant voltage mode. In the constant current mode, a discharged Li-ion battery is charged with constant current available from the external dc source. The MOSFET pass transistor (Q1) may be pulsed “ON” and “OFF” at varying duty cycle by the control signal present at the MAINCHARGEEN input pin. Once the battery voltage reaches it’s termination voltage of 4.1 V or 4.2 V (depending on the connection of the 4.1-VTAP), Si9731 may be placed in the “Constant Voltage” charging mode by taking the CVMODE pin high . Taking CVMODE pin high disables trickle charging and enables the internal battery voltage divider by turning ON Q5. Then the error amplifier will compare divided VBAT+ voltage against an internal precision 1.3-V bandgap reference voltage (see Figure 1). The output of the error amplifier drives the pass transistor Q1 to maintain VBAT+ at the regulated termination voltage. This operation is same as a linear regulator. True Load Disconnect Both the fast charge FET (Q1 in Figure 1) and trickle charge FET (Q2 in Figure 1) incorporate a floating body diode. In their “OFF” state both FETs block current bidirectionally. Note that because of the reverse blocking switches, a Schottky diode in series with the external VCHARGER power supply is not required. Document Number: 71321 S-02258—Rev. A, 28-Sep-00 Si9731 Vishay Siliconix DETAIL OPERATIONAL DESCRIPTION 4.1 VTAP The Si9731’s internal feedback resistors are set to provide 4.2-V charge termination at VBAT+ output if the 4.1 VTAP is left open circuit. Connecting the 4.1 VTAP to VBAT+ configures Si9731 for 4.1-V charge termination at VBAT+. This feature allows Si9731 to accommodate Li-ion batteries requiring 4.1-V or 4.2-V charge termination. Caution : the 4.1 VTAP should not be connected to ground or any other voltage source as this will cause the Si9731 to operate open loop and can result in over charging the battery! Feedback Disconnect Switch The Si9731 includes a feedback disconnect switch (Q5 in Figure 1) connected in series with the device’s internal feedback resistor string. The 42-kW feedback resistor string is connected to ground when both the internal “OK to Charge” signal and the CVMODE pin are at logic high, providing feedback voltage to Si9731’s error amplifier. This action helps prevent the Si9731 from discharging the battery. CHARGERPRESENT and CHARGERPOWERON CHARGERPRESENT and CHARGERPOWERON are open drain outputs, each requiring an external pull-up resistor. pin goes low with CHARGERPRESENT CHARGERPRESENTIN pin goes high, signaling the processor that a charger has been inserted. CHARGERPOWERON Pin goes low when CHARGERPOWERONIN Pin is high, charger voltage is not in UVLO and the battery voltage has increased to above 3.4 V, turning on the system power supply since the battery has been charged up to minimum operating voltage. Input Over-Voltage Detector The external dc source connected to the VCHARGER pin should be at 12 V or less. In the unlikely event that the voltage at VCHARGER pin is at or above 12.8 V (typical), Si9731’s internal Document Number: 71321 S-02258—Rev. A, 28-Sep-00 over voltage detector will turn off MOSFETs Q1, Q2,and Q5 and disable charging. Thermal Shutdown Si9731 also includes a thermal protection circuit that suspends charging through Q1 and Q2 when die temperature exceeds 130_C due to overheating. Once the die temperature cools to below 120_C, the charging will resume. Shutdown Si9731 can be completely turned off by applying 0.4 V or less to the device’s ON/OFF pin. In shutdown mode, Si9731 draws less than 1-mA quiescent current with charger voltage below UVLO, and draws 500 mA when charger voltage is above UVLO. The device is enabled by applying 1.5 V to 12 V at the ON/OFF pin. In applications where the device will always remain enabled, the ON/OFF pin may be connected to the VCHARGER pin. Si9731’s shutdown circuitry includes hysteresis, as such the device will operate properly even if a slow moving signal is applied to the ON/OFF pin. When the device is enabled, the battery voltage sense circuitry draws approximately 25 mA from VBAT. OK to Charge (OTC) Si9731 also includes an internal signal that enables both trickle charge mode and fast charge mode operations, the “OK to Charge” (or OTC) signal. The OTC signal is at logic high if all of the following are satisfied: 1. Battery voltage is below 5 V 2. Charger voltage is greater than 2.6 V but below 12.8 V 3. VCHARGER u VBAT + 40 mV when MAINCHARGEEN = Low VCHARGER u VBAT – 40 mV when MAINCHARGEEN = High 4. ON/OFF pin is at logic high. In order to charge the battery in any manner, the OTC signal has to be high. www.vishay.com 9