DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger General Description Features The AAT3682 is a lithium-ion/polymer linear battery charger. It is designed for compact portable applications with a single-cell battery. The AAT3682 precisely regulates battery charge voltage and charge current, and offers an integrated pass device, minimizing the number of external components required. • • • • • • • • • The AAT3682 charges the battery in three different phases: preconditioning, constant current, and constant voltage. In preconditioning mode, the charge current has two different levels and is controlled by one external pin. Battery charge temperature and charge state are carefully monitored for fault conditions. A battery charge stable monitor output pin is provided to indicate the battery charge status through a display LED or interface to a system controller. The AAT3682 has a sleep mode option for when the input supply is removed. In this mode, it draws only 2.0μA of typical current. The AAT3682 is available in a Pb-free, 16-pin QFN44 package and is specified over the -20°C to +70°C temperature range. • • • • • VIN Range: 4.7V to 6.0V Low Quiescent Current, Typically 0.5mA 1% Accurate Preset Voltage Up to 1A of Charging Current Integrated Pass Device Battery Temperature Monitoring Fast Trickle Charge Option Deep Discharge Cell Conditioning LED Charge Status Output or System Microcontroller Serial Interface Power-On Reset Lower Power Sleep Mode Status Outputs for LED or System Interface Indicates Charge and Fault Conditions Temperature Range: -20°C to +70°C 16-Pin QFN44 Package Applications • • • • • Cellular Telephones Digital Still Cameras Hand-Held PCs MP3 Players Personal Data Assistants (PDAs) Typical Application BAT VP Adapter RSENSE BATT+ R3 COUT = 1μF T2X Gate VP R4 DRV BSENSE BATTR T1 CSI TS VCC STAT C IN = 10μF VSS TEMP LED 1 R2 = 1K RT2 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 1 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Pin Descriptions Pin # Symbol 1 2, 3, 8, 12 TS N/C 4 STAT 5 6 VSS DRV 7 T2X 9 BAT 10 11 13 14 15 16 EP VSS GATE VP CSI BSENSE VCC Function Battery temperature sense input. Not connected. Battery charger status output. Connect an LED in series with 2.2k from STAT to VIN for a visual monitor battery charge state or connect to a microcontroller to monitor battery status. A 100k resistor should be placed between STAT and VIN for this function. Common ground connection. Battery charge control output. Battery trickle charge control input. Connect this pin to VSS to double the battery trickle charge current. Leave this pin floating for normal trickle current (10% of full charge current). To enter microcontroller fast-read status, pull this pin high during power up. Battery charge control output. Current regulated output to charge the battery. For best operation, a 0.1μF ceramic capacitor should be placed between BAT and GND. Common ground connection. Input voltage for biasing the pass device. Battery charge power input. Current sense input. Battery voltage sense input. AAT3682 bias input power. Exposed paddle (bottom); connect to GND directly beneath the package. Pin Configuration QFN44-16 (Top View) 13 15 14 BSENSE 16 1 12 N/C N/C 2 11 GATE N/C 3 10 VSS STAT 4 9 BAT AAT3682 8 7 6 5 N/C T2X DRV VSS 2 VP CSI VCC TS Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Absolute Maximum Ratings1 Symbol Description VIN VCSI VT2X Bias, VBAT TJ VIN Relative to GND CSI to GND T2X to GND BAT to GND Operating Junction Temperature Range Value Units -0.3 to 6.0 -0.3 to VCC + 0.3 -0.3 to 5.5 -0.3 to VCC + 0.3 -40 to 85 °C Value Units 50 2.0 °C/W W V Thermal Information Symbol JA PD Description Maximum Thermal Resistance2, 3 Power Dissipation (TA = 25°C) 1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. Mounted on an FR4 board. 3. Derate 20mW/°C above 25°C. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 3 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Electrical Characteristics1 VIN = 5.0V, TA = -20°C to +70°C, unless otherwise noted. Typical values are at TA = 25°C. Symbol VIN ICC ISLEEP ISTAT(HI) VSTAT(LOW) Description Conditions Operation Input Voltage Operating Current Sleep Mode Current STAT High Level Output Leakage Current STAT Low Level Sink Current VIN VIN VIN VIN VCH Output Charge Voltage Regulation VCS ICH VMIN Charge Current Regulation Charge Current2 Preconditioning Voltage Threshold Trickle Charge Current Regulation Trickle Charge Current Gain Low Temperature Threshold High Temperature Threshold Charge Termination Threshold Voltage Battery Recharge Voltage Threshold Under-Voltage Lockout Over-Voltage Protection Threshold Over-Current Protection Threshold VTRICKLE T2X VTS1 VTS2 VTERM VRCH VUVLO VOVP VOCP Min Typ 4.7 = = = = 5.5V, VCH = 4.2 3.5V, VCH = 4.2 5.5V 5.5V, ISINK = 5mA TA = 25°C VBAT = 4.2V See Note 1 VIN = 5.5V, VCH = 4.2 VIN = 5.5V VCH = 4.2V T2X Floating; VCH = 4.2V T2X = VSS VCH = 4.2V VIN Rising, TA = 25°C 0.5 3.0 -1.0 4.175 4.158 90 3.04 29.1 58.2 4 4.018 3.5 0.3 4.20 4.20 100 3.1 10 1.8 30 60 12 4.1 4.0 4.4 200 Max Units 6.0 3.0 6.0 +1.0 0.6 4.225 4.242 110 1.0 3.16 V mA μA μA V 30.9 61.8 24 4.182 4.5 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 mV A V mV 1. The AAT3682 output charge voltage is specified over the 0°C to 55°C ambient temperature range; operation over -20°C to 70°C is guaranteed by design. 2. 1A of charging current is only for dynamic applications and not DC. In addition, the ambient temperature must be at or below 50°C. 4 V %VCC %VCC mV V V V %VCS DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Typical Characteristics Battery Recharge Threshold Voltage vs.Temperature Regulated Output Voltage vs. Charge Current (RSENSE = 0.15Ω)) Regulated Output Voltage (V) Battery Recharge Threshold Voltage (V) (RSENSE = 0.15Ω) 4.20 4.15 4.10 4.05 4.00 3.95 3.90 3.85 3.80 -25 -50 0 25 50 75 4.25 4.23 4.21 4.19 4.17 4.15 100 0 100 200 Temperature (°C) Regulated Output Voltage vs. Input Voltage Regulated Output Voltage (V) Regulated Output Voltage (V) 4.30 4.20 4.10 4.00 5.0 5.5 6.0 4.200 4.175 4.150 4.125 4.100 -50 -25 Trickle Charge Current (mA) Trickle Charge Threshold Voltage (V) 3.2 3.1 3.0 2.9 Temperature (°C) 50 75 100 (RSENSE = 0.15Ω) 3.3 50 25 Trickle Charge Current vs. Temperature 3.4 25 0 Temperature (°C) (RSENSE = 0.15Ω) 0 700 4.225 6.5 Trickle Charge Threshold Voltage vs.Temperature -25 600 4.250 Input Voltage (V) 2.8 -50 500 (RSENSE = 0.15Ω) 4.40 4.5 400 Regulated Output Voltage vs. Temperature (RSENSE = 0.15Ω) 4.0 300 Charging Current (mA) 75 100 170 165 160 155 150 145 140 135 130 -50 -25 0 25 50 75 100 Temperature (°C) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 5 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Typical Characteristics Charging Current vs. Temperature Charging Current vs. Input Voltage (RSENSE = 0.15Ω) (RSENSE = 0.15Ω with External Schottky) 700 Charging Current (mA) Charging Current (mA) 700 690 680 670 660 650 -50 -25 0 25 50 75 600 500 VBAT = 4.1V 400 300 VBAT = 3.6V 200 100 0 4.0 100 4.5 Temperature (°C) Charging Current vs. Battery Voltage Trickle Charge Current (mA) Charging Current (mA) 600 VIN = 5.5V VIN = 4.75V 400 300 200 100 0 2.5 3.0 3.5 4.0 4.5 170 165 160 155 150 145 140 135 130 5.0 4.0 4.5 Battery Voltage (V) VBAT = 4.0V 300 VBAT = 3.6V 100 5.0 Input Voltage (V) 6 Trickle Charge Current (mA) Charging Current (mA) 500 4.5 6.0 (RSENSE = 0.2Ω; 1.8X Mode) 600 0 4.0 5.5 Trickle Charge Current vs. Input Voltage (RSENSE = 0.2Ω with External Schottky) 200 5.0 Input Voltage (V) Charging Current vs. Input Voltage 400 6.0 (RSENSE = 0.15Ω; 1.8X Mode) 700 VIN = 4.5V 5.5 Trickle Charge Current vs. Input Voltage (RSENSE = 0.15Ω with External Schottky) 500 5.0 Input Voltage (V) 5.5 6.0 104 102 100 98 96 94 4 4.5 5 5.5 Input Voltage (V) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 6 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Typical Characteristics Charging Current vs. Battery Voltage Safe Operating Area (RSENSE = 0.2Ω with External Schottky) (TJ(MAX) = 120°C) Maximum Input Voltage (V) Charging Current (mA) 600 500 400 VIN = 4.5V 300 VIN = 5.5V 200 VIN = 4.75V 100 0 2.5 3.0 3.5 4.0 4.5 5.0 7.0 6.0 5.0 TAMB = 85°C 4.0 TAMB = 70°C TAMB = 40°C TAMB = 50°C 3.0 2.0 1.0 Schottky VF = 0.2V 0.0 0.0 0.2 0.4 0.6 0.8 Charging Current (A) Battery Voltage (V) Safe Operating Area Maximum Input Voltage (V) (TJ(MAX) = 150°C) 6.2 6.0 5.8 TAMB = 85°C 5.6 TAMB = 70°C 5.4 TAMB = <50°C 5.2 Schottky VF = 0.2V 5.0 0 0.2 0.4 0.6 0.8 Charging Current (A) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 7 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Functional Block Diagram VP BAT GATE T2X 2X Trickle Charge Control Loop Select MUX Driver DRV CSI Current Loop Error Amp Microcontroller Status Generator STAT VREF Voltage Loop Error Amp Charge Status Logic Control MUX BSENSE LED Signal Generator Voltage Comparator Microcontroller Read Enable TS VCC T2X VSS Temperature Sense Comparator Power-On Reset Under-Voltage Lock Out Over-Current / Short-Circuit Protection Functional Description Cell Preconditioning The AAT3682 is a linear charger designed for single-cell lithium-ion/polymer batteries. It is a full-featured battery management system IC with multiple levels of power savings, system communication, and protection integrated inside. Refer to the block diagram above and the flow chart and typical charge profile graph (Figures 1 and 2) in this section. Before the start of charging, the AAT3682 checks several conditions in order to maintain a safe charging environment. The input supply must be above the minimum operating voltage, or under-voltage lockout threshold (VUVLO), for the charging sequence to begin. Also, the cell temperature, as reported by a thermistor connected to the TS pin, must be within the proper window for safe charging. 8 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Power On Reset Power On Reset UVLO No VCC > VUVLO Shut Down Shut Down Mode Mode Yes Temperature Temperature Fault Fault No Temperature Test TS > VTS1 TS < VTS2 Yes Preconditioning Test VMIN > VBAT Yes Low Current Conditioning Low Current Charge Conditioning (Trickle Charge) Charge No Current Phase Test VCH > VBAT Yes Current Current Charging Charging Mode Mode No Voltage Phase Test VTERM < I BAT RSENSE Yes Voltage Voltage Charging Charging Mode Mode No < VRCH Charge Complete Charge Complete Latch Off Latch Off Figure 1: AAT3682 Operational Flow Chart. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 9 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Preconditioning (Trickle Charge) Phase Constant Voltage Charging Constant Current Phase Constant Voltage Phase Output Charge Voltage (VCH) Preconditioning Voltage Threshold (VMIN) Regulation Current (ICHARGE(REG)) Charge Cycle Termination, Recharge Sequence Trickle Charge and Termination Threshold Figure 2: Typical Charge Profile. When these conditions have been met and a battery is connected to the BAT pin, the AAT3682 checks the state of the battery. If the cell voltage is below VMIN, the AAT3682 begins preconditioning the cell. This is performed by charging the cell with 10% of the programmed constant current amount. For example, if the programmed charge current is 500mA, then the preconditioning mode (trickle charge) current will be 50mA. Cell preconditioning is a safety precaution for deeply discharged cells and, furthermore, limits power dissipation in the pass transistor when the voltage across the device is largest. The AAT3682 features an optional T2X mode, which allows faster trickle charging at approximately two times the default rate. This mode is selected by connecting the T2X pin to VSS. If an over-temperature fault is triggered, the fast trickle charge will be latched off, and the AAT3682 will continue at the default 10% charge current. Constant Current Charging The cell preconditioning continues until the voltage on the BAT pin reaches VMIN. At this point, the AAT3682 begins constant current charging (fast charging). Current level for this mode is programmed using a current sense resistor RSENSE between the VCC and CSI pins. The CSI pin monitors the voltage across RSENSE to provide feedback for the current control loop. The AAT3682 remains in constant current charge mode until the battery reaches the voltage regulation point, VCH. 10 When the battery voltage reaches VCH during constant current mode, the AAT3682 transitions to constant voltage mode. The regulation voltage is factory programmed to 4.2V. In constant voltage operation, the AAT3682 monitors the cell voltage and terminates the charging cycle when the voltage across RSENSE decreases to approximately 10mV. After the charge cycle is complete, the AAT3682 shuts off the pass device and automatically enters powersaving sleep mode. Either of two possible conditions will bring the IC out of sleep mode: the battery voltage at the BAT pin drops below VRCH (recharge threshold voltage) or the AAT3682 is reset by cycling the input supply through the power-on sequence. Falling below VRCH signals the IC that it is time to initiate a new charge cycle. Sleep Mode When the input supply is disconnected, the device automatically enters power-saving sleep mode. Only consuming an ultra-low 2μA current, the AAT3682 minimizes battery drain when it is not charging. This feature is particularly useful in applications where the input supply level may fall below the battery charge or under-voltage lockout level. In such cases, where the AAT3682 input voltage drops, the device will enter the sleep mode and automatically resume charging once the input supply has recovered from its fault condition. This makes the AAT3682 well suited for USB battery charger applications. Charge Inhibit The AAT3682 charging cycle is fully automatic; however, it is possible to stop the device from charging even when all conditions are met for proper charging. Switching the TS pin to either VIN or GND will force the AAT3682 to turn off the pass device and wait for a voltage between the low and high temperature voltage thresholds. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Resuming Charge and the VRCH Threshold LED Display Charge Status Output The AAT3682 will automatically resume charging under most conditions when a battery charge cycle is interrupted. Events such as an input supply interruption or under voltage, removal and replacement of the battery under charge, or charging a partially drained battery are all possible. The AAT3682 will monitor the battery voltage and automatically resume charging in the appropriate mode based upon the measured battery cell voltage. This feature is useful for systems with an unstable input supply, which could be the case when powering a charger from a USB bus supply. It is also beneficial for charging or “topping off” partially discharged batteries. The only restriction on resuming charge of a battery is that the battery cell voltage must be below the battery recharge voltage threshold (VRCH) specification. There is VRCH threshold hysteresis built into the charge control system. This is done to prevent the charger from erroneously turning on and off once a battery charge cycle is complete. The AAT3682 provides a battery charge status output via the STAT pin. STAT is an open-drain serial data output capable of displaying five distinct status functions with one LED connected between the STAT pin and VP. There are four periods which determine a status word. Under default conditions, each output period is one second long; thus one status word will take four seconds to display through an LED. The five modes include: For example, the AAT3682 has a typical VRCH threshold of 4.1V. A battery under charge is above 4.1V, but is still in the constant voltage mode because it has not yet reached 4.2V to complete the charge cycle. If the battery is removed and then placed back on the charger, the charge cycle will not resume until the battery voltage drops below the VRCH threshold. In another case, a battery under charge is in the constant current mode and the cell voltage is 3.7V when the input supply is inadvertently removed and then restored. The battery is below the VRCH threshold and the charge cycle will immediately resume where it left off. Charge Status 1. 2. 3. 4. 5. Sleep/Charge Complete: The IC goes into Sleep mode when no battery is present -OR- when the charge cycle is complete. Fault: When an over-current (OC) condition is detected by the current sense and control circuit -OR- when an over-voltage (OV) condition is detected at the BAT pin -OR- when a battery over-temperature fault is detected on the TEMP pin. Battery Conditioning: When the charge system is in 1X or 2X trickle charge mode. Constant Current (CC) Mode: When the system is in constant current charge mode. Constant Voltage (CV) Mode: When the system is in constant voltage charge mode. An additional feature of the LED status display is for a Battery Not Detected state. When the AAT3682 senses there is no battery connected to the BAT pin, the STAT output will turn the LED on and off at a rate dependent on the size of the output capacitor being used. The LED cycles on for two periods then remains off for two periods. See Figure 3 below. LED Display Output Status on/off on/off on/off on/off ON Sleep / Charge Complete off / off / off / off Temp., OC, OV Fault on / on / off / off Battery Conditioning on / on / on / on Constant Current Mode on / on / on / off Constant Voltage Mode on / off / off / off OFF ON OFF ON OFF ON OFF ON OFF Figure 3: LED Display Output. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 11 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger High-Speed Data Reporting An optional system microcontroller interface can be enabled by pulling the T2X pin up to 4.5V to 5.5V during the power-up sequence. The T2X pin should be pulled high with the use of a 100k resistor. If the input supply to VIN will not exceed 5.5V, then the T2X pin may be tied directly to VIN through a 100k resistor. Since this is a TTL level circuit, it may not be pulled higher than 5.5V without risk of damage to the device. When the high-speed data report feature is enabled, the STAT output periods are sped up to 40μs, making the total status word 160μs in length. See Figure 4 below. An additional feature is the Output Status for the Battery Not Detected state. When the AAT3682 senses there is no battery connected to the BAT pin, the STAT pin cycles for two periods, then remains off for two periods. When in high-speed data reporting, the AAT3682 will only trickle charge at the 2X trickle charge level. This is because the T2X pin is pulled high to enable the highspeed data reporting. A status display LED may not be connected to the STAT pin when the high-speed data reporting is being utilized. If both display modes are required, the display LED must be switched out of the circuit before the T2X pin is pulled high. Failing to do so could cause problems with the high-speed switching control circuits internal to the AAT3682. Charge Complete LED Status Mode A simplified LED status can be obtained by configuring the AAT3682 for high-speed data reporting mode (T2X tied to VCC) and installing a 0.047μF capacitor from the STAT pin to the VSS pin (see Figure 5). In this configuration, the LED will be illuminated for all modes except the Charge Status Sleep / Charge Complete Sleep/Charge Complete mode. In addition, the T2X input must be tied to VCC through a 100k resistor. In this mode, the trickle charge current will be 1.8X the normal trickle charge level. To reset the trickle charge current to the 1X level, the TS input must be temporarily toggled low. Removing C3 forces the LED status to gradually dim as the battery becomes fully charged (see Figure 5). Protection Circuitry The AAT3682 is a highly integrated battery management system IC including several protection features. In addition to battery temperature monitoring, the IC constantly monitors for over-current and over-voltage conditions; if an over-current situation occurs, the AAT3682 latches off the pass device to prevent damage to the battery or the system, and enters shutdown mode until the overcurrent event is terminated. An over-voltage condition is defined as a condition where the voltage on the BAT pin exceeds the maximum battery charge voltage. If an overvoltage condition occurs, the IC turns off the pass device until voltage on the BAT pin drops below the maximum battery charge constant voltage threshold. The AAT3682 will resume normal operation after the over-current or over-voltage condition is removed. During an over-current or over-voltage event, the STAT will report a FAULT signal. In the event of a battery over-temperature condition, the IC will turn off the pass device and report a FAULT signal on the STAT pin. After the system recovers from a temperature fault, the IC will resume operation in the 1X trickle charge mode to prevent damage to the system in the event a defective battery is placed under charge. Once the battery voltage rises above the trickle charge to constant current charge threshold, the IC will resume the constant current mode. Output Status STAT Level HI / HI / HI / HI Temp., OC, OV Fault LO / LO / HI / HI Battery Conditioning LO / LO / LO / LO Constant Current Mode LO / LO / LO / HI Constant Voltage Mode LO / HI / HI / HI Figure 4: Microcontroller Interface Logic Output. 12 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger VIN 2 1 C1 22μF R1 2.2K R5 100K C5 4.7μF 13 14 15 16 J1 GND R2 0.2Ω N/C GATE VSS BAT 12 11 10 9 J2 D1 8 7 6 5 R6 100K Remove capacitor for progressive dimming TS N/C N/C STAT 3 100K 1 C2 10μF 1 2 3 R4 1K C3 47nF R7 C4 1000pF R3 1K N/C T2X DRV VSS D2 Green LED VP CSI BSENSE VCC 1 2 3 4 U1 AAT3682 S1 2 SW-T2X Figure 5: Evaluation Board Schematic. Applications Information Choosing a Sense Resistor The charging rate recommended by lithium-ion/polymer cell vendors is normally 1C, with a 2C absolute maximum rating. Charging at the highest recommended rate offers the advantage of shortened charging time without decreasing the battery’s lifespan. This means that the suggested fast charge rate for a 500mAH battery pack is 500mA. Refer to the Safe Operating Area curves in the Typical Characteristics section of this datasheet to determine the maximum allowable charge current for a given input voltage. The current sense resistor, RSENSE, programs the charge current according to the following equation: RSENSE = VCC - VCSI ICHARGE Where ICHARGE is the desired typical charge current during constant current charge mode. VCC - VCSI is the voltage across RSENSE, shown in the Electrical Characteristics table as VCS. To program a nominal 500mA charge cur- rent during fast charge, a 200m value resistor should be selected. Calculate the worst case power dissipated in the sense resistor according to the following equation: P= VCS2 0.1V2 = = 50mW RSENSE 0.2Ω A 500mW LRC type sense resistor from IRC is adequate for this purpose. Higher value sense resistors can be used, decreasing the power dissipated in the sense resistor and pass transistor. The drawback of higher value sense resistors is that the charge cycle time is increased, so tradeoffs should be considered when optimizing the design. Thermistor The AAT3682 checks battery temperature before starting the charge cycle, as well as during all stages of charging. This is accomplished by monitoring the voltage at the TS pin. Either a negative temperature coefficient thermistor (NTC) or positive-temperature coefficient thermistor (PTC) can be used because the AAT3682 checks to see Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 13 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger that the voltage at TS is within a voltage window bounded by VTS1 and VTS2. Please see the following equations for specifying resistors: RT1 and RT2 for use with NTC Thermistor: RT1 = RT2 = 5 ∙ RTH ∙ RTC 3 · (RTC - RTH) 5 ∙ RTH ∙ RTC (2 ∙ RTC) - (7 ∙ RTH) RT1 and RT2 for use with PTC Thermistor: RT1 = RT2 = 5 ∙ RTH ∙ RTC 3 · (RTH - RTC) 5 ∙ RTH ∙ RTC (2 ∙ RTH) - (7 ∙ RTC) Where RTC is the thermistor’s cold temperature resistance and RTH is the thermistor’s hot temperature resistance. See thermistor specifications for additional information. To ensure there is no dependence on the input supply changes, connect divider between VCC and VSS. Disabling the temperature-monitoring function is achieved by applying a voltage between VTS1 and VTS2 on the TS pin. Capacitor Selection Input Capacitor In general, it is good design practice to place a decoupling capacitor between the VCC and VSS pins. An input capacitor in the range of 1μF to 10μF is recommended. If the source supply is unregulated, it may be necessary to increase the capacitance to keep the input voltage above the under-voltage lockout threshold. If the AAT3682 is to be used in a system with an external power supply source, such as a typical AC-to-DC wall adapter, then a CIN capacitor in the range of 10μF should be used. A larger input capacitor in this application will minimize switching or power bounce effects when the power supply is “hot plugged” in. Output Capacitor The AAT3682 does not need an output capacitor for stability of the device itself. However, a capacitor connected 14 between BAT and VSS will control the output voltage when the AAT3682 is powered up when no battery is connected. The AAT3682 can become unstable if a high impedance load is placed across the BAT pin to VSS. Such a case is possible with aging li-ion/poly battery cells. As cells age through repeated charge and discharge cycles, the internal impedance can rise over time. A 10μF or larger output capacitor will compensate for the adverse effects of a high impedance load and assure device stability over all operating conditions. Power Dissipation The voltage drop across the VP and BAT pins multiplied times the charge current is used to determine the internal power dissipation. The maximum power dissipation occurs when the input voltage is at a maximum and the battery voltage is at the minimum preconditioning voltage threshold. This power is then multiplied times the package theta to determine the maximum junction temperature. The worst case power junction temperature is calculated as follows: PMAX = (VIN(MAX) - VSENSE - VSCHOTTKY - VBAT(MIN)) ⋅ ICHG(MAX) = (5.5V - 0.1V - 0.2V - 3.04V) ⋅ 550mA = 1.2W This equation can be used to determine the maximum input voltage given the maximum junction and ambient temperature and desired charge current. VIN(MAX) = = TJ(MAX) - TAMB + VBAT + VSCHOTTKY + VCS θ ⋅ ICHG(MAX) 120°C - 70°C + 3.1V + 0.2V + 0.1V 50°C/W ⋅ 500mA = 5.3V Operation Under No-Load Under no-load conditions (i.e., when the AAT3682 is powered with no battery connected between the BAT pin and VSS), the output capacitor is charged up very quickly by the trickle charge control circuit to the BAT pin until the output reaches the recharge threshold (VRCH). At this point, the AAT3682 will drop into sleep mode. The output capacitor will discharge slowly by the capacitor’s own internal leakage until the voltage seen at the BAT pin drops below the VRCH threshold. This 100mV cycle will Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger continue at approximately 3Hz with a 0.1μF capacitor connected. A larger capacitor value will produce a slower voltage cycle. This operation mode can be observed by viewing the STAT LED blinking on and off at the rate established by the COUT value. For desktop charger applications, where it might not be desirable to have a “charger ready” blinking LED, a large COUT capacitor in the range of 100μF or more would prevent the operation of this mode. A reverse blocking diode is generally required for the circuit shown in Figure 5. The blocking diode gives the system protection from a shorted input. If there is no other protection in the system, a shorted input could discharge the battery through the body diode of the internal pass MOSFET. If a reverse blocking diode is added to the system, a device should be chosen that can withstand the maximum constant current charge current at the maximum system ambient temperature. The AAT3682 features a charge status output. Connecting a LED to the STAT pin will display all the three conditions of battery operation. Once the adapter is connected to the battery charger, the LED will be fully illuminated. As the battery charges, the LED will gradually dim as it transitions to constant current mode and to constant voltage mode. Table 1 summarizes the conditions. Additionally, the blocking diode will prevent the battery from being discharged to the UVLO level by the AAT3682 in the event that power is removed from the input to the AAT3682. For this reason, the blocking diode must be placed in the location shown in Figure 5. Charge Status LED Display No Battery Connected Battery Condition Constant Current Constant Voltage Sleep/Charge Complete Blinking 100% LED Light 75% LED Light 25% LED Light Off Table 1: Charging Status. Diode Selection Typically, a Schottky diode is used in reverse current blocking applications with the AAT3682. Other lower cost rectifier type diodes may also be used if sufficient input power supply headroom is available. The blocking diode selection should based on merits of the device forward voltage (VF), current rating, input supply level versus the maximum battery charge voltage, and cost. For applications where gradual dimming of the LED is not desired, adding C3 (refer to Figure 5) between the STAT pin and VSS will alter the charging status. In addition, the AAT3682 must be configured to operate in the high frequency STAT mode by connecting the T2X pin to VCC via 100k resistor. First, one must determine the appropriate minimum diode forward voltage drop: As the battery is transitioning from trickle charge to constant current charge and constant voltage, the LED will remain illuminated. Once the battery is fully charged, the LED will shut off, indicating completion of charge. Table 2 summarizes the conditions. VIN(MIN) = Minimum input supply level VBAT(MAX) = Maximum battery charge voltage required VF(TRAN) = Pass transistor forward voltage drop VF(DIODE) = Blocking diode forward voltage Charge Status LED Display No Battery Connected Battery Condition Constant Current Constant Voltage Sleep/Charge Complete Blinking On On On Off VIN(MIN) = VBAT(MAX) + VF(TRAN) + VF(DIODE) Where: Based on the maximum constant current charge level set for the system, the next step is to determine the minimum current rating and power handling capacity for the blocking diode. The constant current charge level itself will dictate what the minimum current rating must be for a given blocking diode. The minimum power handling capacity must be calculated based on the constant current amplitude and the diode forward voltage (VF): Table 2: Charging Status With C3 Connected. PD(MIN) = VF ICC Where: Reverse Current Blocking Diode PD(MIN) = Minimum power rating for a diode selection Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 15 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger VF = Diode forward voltage ICC = Constant current charge level for the system Rectifier Diodes Schottky diodes are selected for this application because they have a low forward voltage drop, typically between 0.3V and 0.4V. A lower VF permits a lower voltage drop at the constant current charge level set by the system; less power will be dissipated in this element of the circuit. A Schottky diode allows for lower power dissipation, smaller component package sizes, and greater circuit layout densities. Any general purpose rectifier diode can be used with the AAT3682 application circuit in place of a higher cost Schottky diode. The design trade-off is that a rectifier diode has a high forward voltage drop. VF for a typical silicon rectifier diode is in the range of 0.7V. A higher VF will place an input supply voltage requirement for the battery charger system. This will also require a higher power rated diode since the voltage drop at the constant current charge amplitude will be greater. Refer to the previously stated equations to calculate the minimum VIN and diode PD for a given application. Figure 6: Evaluation Board Top Side Layout. Figure 7: Evaluation Board Bottom Side Layout. Schottky Diodes 16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Reference Symbol Description Footprint Part Number Manufacturer U1 C1 C2 C3 R1 R2 R3 R4 R5 R6 R7 J1 J2 S1 D1 D2 Battery Charger AAT3682 Ceramic Capacitor 20μF-10V-X5R Ceramic Capacitor 10μF-10V-X5R Ceramic Capacitor 0.047μF-10V-X7R Resistor 2.2k 1/4W Current Sensing Resistor 0.2 1/4W Resistor 1.0k 1% 1/4W Resistor 1.0k 1% 1/4W Resistor 100k 1% 1/4W Resistor 100k 1% 1/4W Resistor 100k 1% 1/4W 4-Pin Socket Connector 6-Pin Socket Connector Jumper Stand Switch Green LED 3.0A Schottky Diode QFN44-16 1210 0805 0805 0402 0805 0402 0402 0402 0402 0402 4 Pin 6 Pin 2mm Jumper 1206 SMA AAT3682-4.2 GRM32ER61A226KA65L GRM21BR61A106KE19L VJ0805Y473KXQA CRCW04022211F RL1220S-R20-F CRCW04021003F CRCW04021001F CRCW04021003F CRCW04021003F CRCW04021003F 277-1273-ND 277-1274-ND S2105-40-ND L62215CT-ND B340LADITR-ND Skyworks Murata Vishay SSM Susumu Vishay Chicago Miniature Diodes Incorporated Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012 17 DATA SHEET AAT3682 Li-Ion/Polymer Linear Battery Charger Ordering Information Output Voltage Package Marking1 Part Number (Tape and Reel)2 4.2V QFN44-16 MGXXY AAT3682ISN-4.2-T1 Skyworks Green™ products are compliant with all applicable legislation and are halogen-free. For additional information, refer to Skyworks Definition of Green™, document number SQ04-0074. Package Information3 2.400 ± 0.050 0.550 ± 0.020 0.330 ± 0.075 13 2.400 ± 0.050 1 4 9 8 4.000 ± 0.050 Pin 1 Identification 16 C0.3 0.650 BSC 5 2.280 REF Top View 0.025 ± 0.025 Bottom View 0.214 ± 0.036 0.900 ± 0.100 4.000 ± 0.050 Pin 1 Dot By Marking Side View All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection. Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes. No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. 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Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. 18 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 201884A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 17, 2012