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SI9731
Vishay Siliconix
mP Controlled Battery Charger For 1-Cell Li-ion or 1-Cell to 3-Cell NiCd/NiMH Batteries
FEATURES
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 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)
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 Fast Charge B a t t e r y
ON/OFF
Trickle Charge
TRICKLECHARGEENABLE CVMODE FAST CHARGE GND Charge Control 4.1/4.2 V_TAP
Document Number: 71321 S-02258--Rev. A, 28-Sep-00
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SI9731
Vishay Siliconix
ABSOLUTE MAXIMUM RATINGS
Voltages Referenced to GND = 0 V 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) 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 Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65 to 150_C Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150_C 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 Symbol
-40_C t TA t +85_C 3.0 V v VCHARGER v 6.5 V, VON/OFF = 1.5 V
Mina
Typb
Maxa
Unit
External Charger Voltage Under Voltage Lockout on Charger UVLO Hysteresis Regulated Output Voltage 4.1 V_TAP to VBAT
VCHARGER VUVLO UVLOHYST VCHARGER = 5.0 V IBAT+ = 1 mA MAINCHARGEREN = 5.0 V CVMODE = 5.0 V -10_C t TA t +40_C -40_C t TA t +85_C -10_C t TA t +40_C -40_C t TA t +85_C Rising Edge of Battery Charger
3.0 2.45 70 4.050 4.025 4.150 4.125 4.70 2.6 90 4.1 4.1 4.2 4.2 4.95 0.11 Rising Edge, VBAT+ Latch Comparator Offset Voltage, VCHARGER - VBAT+ MAINCHARGEEN-- High MAINCHARGEEN-- Low 3.32 -0.08 0.01 3.41 -0.04 0.04 0.07
12 2.75 110 4.150 4.150 4.250 4.250 5.15
V mV
VTERM+ Regulated Output Voltage 4.1 V_TAP Open Battery Over Voltage Protection Battery Over Voltage Hysteresis Battery Minimum Operating Voltage Charger Voltage to Battery Voltage Comparator Offset Charger Voltage to Battery Voltage Comparator Hysteresis Quiescent Current (Normal Mode) Quiescent Current (Shutdown Mode) Feedback Resistor IIN(VCHARGER Pin) ON-Mode IIN(VCHARGER Pin) OFF-Mode RFB1 RFB2 + RFB3 VOVP VOVP_HYS VBAT(min) VOS_CB
Rising Edge of VBAT+
V 3.50 -0.01 0.08
1 mA v IBAT+ v 600 mA VON/OFF = 0 V, VCHARGER = 4.5 V Pin 12 to Pin 14 Pin 12 to GND VON/OFF = 0 V -1 -1
1 0.1 1 41 0.1 0.1
3 1
mA mA kW W
1 2 mA
Battery Leakage Current
IPIN13 + IPIN14
VBAT+ = 4.2 V
VCHARGER = 0V
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Document Number: 71321 S-02258--Rev. A, 28-Sep-00
SI9731
Vishay Siliconix
SPECIFICATIONS
Test Conditions Unless Specified Parameter Symbol
-40_C t TA t +85_C 3.0 V v VCHARGER v 6.5 V, VON/OFF = 1.5 V
Mina
Typb
Maxa
Unit
Q1 ON Resistance Q2 ON Resistance Q5 ON Resistancec
Q1 rDS(on) Q2 rDS(on) Q5 rDS(on) VCHARGER(OVD) VCHARGER(OVD)
_HYS
MAINCHARGEREN w 1.5 V VCHARGER = 4.5 V TRICKLECHARGEEN v 0.4 V CVMODE w 1.5 V Rising Edge of Battery Charger 12.2 6 6 12.8 0.4
400 10
mW
W
Over Voltage Detect Threshold Over Voltage Detect Threshold Hysteresis Output High Leakage Current Output Low Voltage Logic Low Voltage Logic High Voltage Pull Down Current
13.4 V
CHARGERPRESENT and CHARGERPOWER_ON
IOH VOL VIL VIH IP/D TS/D THYST VON/OFF(high) VON/OFF(low) VON/OFF(hyst)
VOH = 6.5 V IOL = 1 mA
0.1
2
mA
0.4 0.4 1.5 0.7 130 10 1.5 0.3 100 V mV 10 mA _C _ V
CHARGERPRESENTIN, CHARGERPOWER_ONIN, TRICKLECHARGEEN, MAINCHARGEEN or CVMODE
Thermal Shutdown Temperaturec Thermal Shutdown Hysteresisc Shutdown High Voltage Logic Level Shutdown Low Voltage Logic Level Shutdown Hysteresis
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
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SI9731
Vishay Siliconix
PIN CONFIGURATION
TSSOP-16
CHARGERPRESENTIN CHARGERPOWER_ONIN VCHARGER ON/OFF TRICKLECHARGEEN CVMODE MAINCHARGEEN (N/C) 1 2 3 4 5 6 7 8 Top View 16 15 14 CHARGERPRESENT = (XCHARGERPRESENT) CHARGERPOWER_ON = (XCHARGERPOWER_ON) VBAT+ TRICKLE_VBAT 4.1 V_TAP GND (N/C) VREF
SI9731DQ
13 12 11 10 9
Ordering Information Part Number
SI9731DQ
Temperature Range
-40 to 85_C
Package
Tape and Reel
Eval Kit
SI9731DB
Temperature Range
-40 to 85_C
Board Type
Surface Mount
PIN DESCRIPTION
Pin Number
1 2 3 4 5 6 7 8, 10 9 11 12 13 14 15 16
Name
CHARGERPRESENTIN CHARGERPOWER_ONIN VCHARGER ON/OFF TRICKLECHARGEEN CVMODE MAINCHARGEEN N/C VREF GND 4.1 V_TAP TRICKLE_VBAT VBAT+ CHARGERPOWER_ON CHARGERPRESENT Logic input for CHARGERPRESENT output Logic input for CHARGERPOWER_ON output External charger
Function
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. Do not connect external circuitry to this pin. Circuitry internal to the IC is connected to this pin. Internal 1.30-V precision bandgap reference voltage. Do not apply loads to this pin. Low impedance system ground Connect this pin to VBAT+ for 4.1-V charge termination in constant voltage mode Resistor connected between this pin and VBAT to limit the trickle charge current. Charger output connected to battery's positive terminal Open drain logic output Open drain logic output
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Document Number: 71321 S-02258--Rev. A, 28-Sep-00
SI9731
Vishay Siliconix
TABLE 1: BATTERY CHARGING CONTROL LOGIC (NOMINAL VOLTAGE VALUES)
VCHARGER
Not Present Not Present OK to Chargea Over Voltage VCHARGER u12.8 V
TRICKLE CHARGEEN
X X X X LOW HIGH LOW
CVMODE
X X X X LOW LOW LOW LOW HIGH HIGH HIGH HIGH
MAIN CHARGEEN
X X X X LOW LOW HIGH HIGH LOW LOW HIGH HIGH
ON/OFF
X X X LOW HIGH HIGH HIGH HIGH HIGH HIGH HIGH HIGH
Q1b
OFF OFF OFF OFF OFF OFF ON ON OFF OFF ON ON
Q2
OFF OFF OFF OFF ON OFF OFF OFF OFF OFF OFF OFF Not Charging Not Charging Not Charging
Mode
Not Charging (Shutdown) Trickle Charge Not Charging (Current pulse off during Constant Current Charge) 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)
Present OK to Chargea
HIGH LOW HIGH LOW HIGH
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
Q1 Drive (Digital)
LOW LOW HIGH HIGH
Output of Error Amplifier
LOW Intermediate LOW HIGH
Q1 Drive
LOW (fully off) Intermediate (linear mode) HIGH (fully on) Should Never Happen
Document Number: 71321 S-02258--Rev. A, 28-Sep-00
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SI9731
Vishay Siliconix
TYPICAL CHARACTERISTICS (25_C UNLESS NOTED)
VBAT (CV Mode) vs. VCHARGER
4.22 4.1 TAP Open 4.20 4.18 V BAT (V) - 4.16 4.14 4.12 4.10 4.08 3 6 VCHARGER (V) 9 12 V BAT (V) - 4.20 4.18 4.16 4.14 4.12 4.1 TAP to VBAT 4.10 4.08 4.06 -40 4.1 TAP to VBAT 4.22 4.1 TAP Open
VBAT (CV Mode) vs. Temperature
-15
10
35
60
85
Temperature (_C)
Charger UVLO Rising vs. Temperature
2.75 1.0
VBAT Leakage vs. Temperature
VCHARGER = 0 V VBAT = 4.2 V
2.70 V CHARGER - (V) Current V BAT (V) - -15 10 35 60 85
0.8
2.65
0.6
2.60
0.4
2.55 0.2
2.50
2.45 -40
0.0 -40
-20
0
20
40
60
80
100
Temperature (_C)
Temperature (_C)
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Document Number: 71321 S-02258--Rev. A, 28-Sep-00
SI9731
Vishay Siliconix
BLOCK DIAGRAM AND TYPICAL APPLICATION CIRCUIT
16 CHARGERPRESENT
CHARGERPRESENTIN
1
Q3
15 2
CHARGERPOWER_ON
CHARGERPOWER_ONIN
Q4
Latch 4
ON/OFF
100 kW 3
1 MW Battery Min Voltage UVL
+
-
+
3.4 V 14 VBAT+ VBAT
VCHARGER CIN 2.2 mfd
2.6 V
- OVP -
Circuit Power + OK to Charge (OTC) - Battery Over Voltage 5V
COUT 2.2 mfd
12.8 V
+
+
56 W
B a t t e r y
- Q2 Trickle Charge Q1 Fast Charge RFB1 12 RFB2 4.1 V_TAP 13 Trickle_VBAT
TRICKLECHARGEEN
5
RFB3 CVMODE 6 Digital
+ Q5 11 Enable GND
MAINCHARGEEN
7 -
+
Voltage Generator
2.6 V 3.4 V 5V 12.8 V
Temp OK
Analog E/A
9
VREF 0.1 mfd
Temp Sensor
Ref Voltage 8 N/C
1.3 V 10 N/C
FIGURE 1.
Document Number: 71321 S-02258--Rev. A, 28-Sep-00 www.vishay.com
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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. 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.
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.
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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! 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.
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
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