PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger General Description Features The AAT3620 BatteryManagerTM is a member of AnalogicTech's Total Power Management ICTM family. With the many functions added to mobile devices such as color display, camera with flash, organizer, video, etc, the battery capacity must keep pace with the power requirements. The AAT3620 is the ideal solution for high capacity Li+ batteries and can supply up to 2.0A charge current with minimal thermal impact to the system. * * * * * * * * The AAT3620 is a PWM switch mode / linear charger with high charge efficiency at the full constant current (fast charge) rate. Based on a 1.5MHz PWM step-down "buck" converter, the AAT3620 PWM switch mode controls the constant current charge mode up to 2.0A, and automatically switches to linear mode charging during the battery conditioning low level current and the light load end of charge current termination region. The full charge rate and the end of charge current can be programmed with separate external resistors. A shared charge current indication pin is available for a Coulomb counter. * * * * * * * * 4.3V~6.0V Input Range Up to 2.0A Charge Current Capability 1.5MHz PWM/Linear Charger Over 90% Full Rate Charge Efficiency Integrated Switching Device Integrated Sense Resistor Built-in Reverse Blocking Feature Battery Preconditioning/Constant Voltage/Constant Current Charge Mode Programmable End of Charge Current 1% Constant Voltage Mode Regulation Built-in Programmable Charging Timer Charge Current Indication Pin Over-Voltage, Over-Current, and Over-Temperature Protection Battery Over-Temperature Protection Power-On Reset and Soft-Start TDFN33-14 Package Applications Battery charge temperature and charge state are fully monitored for fault conditions. In the event of an overcurrent, over-voltage, short-circuit or over-temperature failure, the device will automatically shut down. A status monitor output pin is provided to indicate the battery charge status and power source status though a display LED. * * * * * Digital Camcorders Point of Service (POS) Portable DVD Players Portable Hand-held Solutions Portable Media Player The AAT3620 is available in a thermally enhanced, spacesaving 14-pin 3x3mm TDFN package that includes all essential components for a switch-mode battery charger. Typical Application 4.7H LX CS Adapter BATT + VPIN 22F 0.1F Charge Enable BAT VCC Battery Pack + 22F to 47F EN BATT- - PGND Timer Disable VPIN CT RT 0.1F TEMP TS Charging Status 1 STAT1 ISET Charging Status 2 STAT2 TERM Charge Current Set Termination Current Set and Charge Current Indicator GND RTERM 3620.2009.12.1.3 www.analogictech.com R SET 1 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Pin Description Pin# Name Type 1 2 3 4 5 6 VPIN PGND GND VCC EN ISET In Ground Ground In In In 7 CT In/Out 8 9 STAT2 STAT1 Out Out 10 TERM In/Out 11 TS In/Out 12 13 14 BAT CS LX Out In In/Out EP EP Ground Function Adapter power input. Power ground. Analog ground connection. Supply Input. Charge enable input, active high, with internal pull-up (to VPIN). Connect RSET resistor to pin to set constant current charge current. Timer pin: connect timing capacitor here for charge timer function; connect to ground to disables the timer function. Battery charge status 2 indicator pin to drive an LED, open-drain. Battery charge status 1 indicator pin to drive an LED, open-drain. Connect RTERM resistor to pin to set termination current. Charging current can be monitor with this pin. Leave OPEN to set to 200mA default termination current. Battery pack temperature sensing input. To disable TS function, pull up to VCC through 10k resistor. Battery positive terminal connecting pin. Return pin for inductor for internal current sensing Switching node. The exposed thermal pad (EP) must be connected to board ground plane and pins 2 and 3. The ground plane should include a large exposed copper pad under the package for thermal dissipation (see package outline). Pin Configuration TDFN33-14 (Top View) VPIN PGND GND VCC EN ISET CT 2 1 14 2 13 3 4 12 EP 11 5 10 6 9 7 8 LX CS BAT TS TERM STAT1 STAT2 www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Absolute Maximum Ratings1 Symbol VP VN TJ PD TLEAD Description VPIN, LX Other pins Operating Junction Temperature Range Maximum Power Dissipation Maximum Soldering Temperature (at Leads) Value Units -0.3 to 6.5 -0.3 to VP + 0.3 -40 to 150 2.5 300 V V C W C Value Units 50 2 C/W W Thermal Information Symbol JA PD Description Maximum Thermal Resistance (3x3mm TDFN-14)2 Maximum Power Dissipation3 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 2.7mW/C above 25C ambient temperature. 3620.2009.12.1.3 www.analogictech.com 3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Electrical Characteristics1 VIN = 5.5V, TA = -25C to 85C; unless otherwise noted, typical values are at TA = 25C. Symbol Description Conditions Operation VIN Adapter Input Voltage VVIN_UVLO Input Under-Voltage Lockout VPIN Rising Hysteresis VVIN_SLEEP Input Sleep Voltage No Charge if VVIN < VVIN_SLEEP Operating Supply Current Standby Supply Current Shutdown Supply Current Forward Leakage Current, Measured IFWD_LKG from LX to Ground Reverse Leakage Current, Measured IREV_LKG from LX to VIN IBAT_LKG Bat Pin Leakage Current Internal PMOS On Resistance RDS(ON) Internal NMOS On Resistance fSW PWM Switching Frequency Charge Regulation VBAT_REG Output Charge Voltage Regulation EN = Low or High, VIN = 0V, LX = 5.5V VBAT = 4.2V, VIN = 0V or open VIN = 5.5V VIN = 5.5V VBAT = 3.6V VBAT_BC Battery Conditioning Battery Voltage Threshold ICH_BC Battery Conditioning Charge Current When VBAT < VBAT_BC ICH_BC_TYP Typical Battery Conditioning Charge Current Setting Range ICH_CC ICH_CC_TYP tCH_CCFAST tCH_CV VBAT_RCH Charging Soft-Start Delay Constant-Current Battery Charge Current Typical Constant-Current Battery Charge Current Setting Range ITERM Charge Termination Threshold Current ITERM_TYP Typical Termination Threshold Current Setting Range Max Units 6.0 4.3 V V mV VBAT + 0.2 5 2 10 mA mA A 1 A 1 A 1.2 170 120 1.5 1 300 250 1.8 A m m MHz 4.158 4.20 4.242 V 100 2.4 2.6 V us 2.8 ICH_ CC x 0.1 V A 200 mA Stop Charge if Preconditioning Time is more than tCH_CV -15% 0.25 x CCT +15% Minute/nF When VBAT_BC < VBAT < VBAT_REG -15% ICH_CC +15 % 2 A +15% Hour/nF +15% Hour/nF 1 Fast Constant Current Charge Time Out Battery Recharge Voltage Threshold 150 VBAT + 0.05 100 Battery Conditioning Time Out Constant Voltage Charge Time Out 4.3 3.5 EN = Low, LX = 5.5V Delay of Charge from EN, or VVIN_UVLO, or VVIN_ADPP Preconditioning Battery Charge when VBAT < VBAT_BC tCH_BC Typ EN = High, Charge Current = 200mA EN = High, No Charge EN = Low, LX Floating IVIN_OP IVIN_STBY IVIN_SHDN tSOFT_START Min Stop Charge if Fast Charge Time is more than tCH_CCFAST Stop Charge if Charge Time is more than tCH_CV If VBAT Falls Below VBAT_RCH, Recharge Starts Terminate CV Charge if ICH < ITERM -15% -15% -10 50 0.02 x CCT 0.03 x CCT VBAT_REG - 0.1 RTERM x 10-6 V 10 % 200 mA 1. Specification over the -25C to +85C operating temperature range is assured by design, characterization and correlation with statistical process controls. 4 www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Electrical Characteristics1 VIN = 5.5V, TA = -25C to 85C; unless otherwise noted, typical values are at TA = 25C. Symbol Description Conditions Logic and Status Input/Output VHIGH EN Input Low Threshold VLOW EN Input Low Threshold IEN ISLEAK ISTATx tSTAT_PULSE fSTAT_FLASH Min Typ Max 1.6 EN Pin Supply Current STAT1, STAT2 Pin Leakage Current STAT1 and STAT2 Pin Current Sink Capability STAT Pulse Width STAT Pulse Frequency EN = VIN EN = 0V When output FET is off 0.1 0.6 In fault conditions In fault conditions 0.5 1 0.4 1 10 1 10 Units V V A A A mA s Hz Protection VBAT_OVP IOCP_LMT2 VBAT_OVP IDATA Battery Over-Voltage Protection Threshold Over-Current Protection Threshold and Limit VTS1 TS Hot Temperature Fault VTS2 TS Cold Temperature Fault Threshold TTH TTH HYS Thermal Shutdown Thermal Shutdown Hysteresis VCT_DIS Charge Timer Disable Threshold VBAT_REG + 0.2 No charge if VBAT > VBAT_OVP Threshold Hysteresis Threshold Hysteresis No timer out if CT voltage holds to be less than VCT_DIS V 2.46 3.0 4.0 A 29.1 30 50 60 50 140 15 30.9 % VIN mV 61.8 % VIN mV C C 0.4 V 58.2 1. Specification over the -25C to +85C operating temperature range is assured by design, characterization and correlation with statistical process controls. 3620.2009.12.1.3 www.analogictech.com 5 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Typical Characteristics Charging Current vs. Battery Voltage Constant-Current Charge Mode Current vs. ISET Resistor (VIN = 5V; VBAT = 3.5V) Fast Charge Current (mA) Charging Current (mA) 2400 2100 1800 1500 1200 900 600 85C 25C -25C 300 0 2.2 2.5 2.8 3.1 3.4 3.7 4.0 10000 1000 100 10 10 4.3 100 ) Set Resistor (K Battery Voltage (V) Termination Current vs. Temperature Recharge Voltage vs. Temperature (VIN = 5V) 4.080 64 62 60 58 56 54 52 50 48 46 44 42 40 End of Charge Voltage (V) Termination Current (mA) (VIN = 5V; RTERM = 49.9K) 4.075 4.070 4.065 4.060 4.055 4.050 -40 -15 10 35 60 85 -40 35 60 85 3.0 2.64 Shutdown Current (A) Preconditioning Rising Threshold Voltage (V) (VIN = 5.5V) 2.63 2.62 2.61 2.60 2.59 2.58 2.57 2.5 2.0 1.5 1.0 -25C 25C 85C 0.5 0.0 -15 10 35 60 85 4.5 5.0 5.5 6.0 Input Voltage (V) Temperature (C) 6 10 Shutdown Current vs. Input Voltage Preconditioning Rising Threshold Voltage vs. Temperature 2.56 -40 -15 Temperature (C) Temperature (C) www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Charge Current vs. Input Voltage Charge Current vs. Input Voltage (T = -25C) (T = 85C) 2400 2500 2100 Charge Current (mA) Battery Charging Current (mA) Typical Characteristics 1800 1500 1200 900 VBAT = 2.7V VBAT = 3.3V VBAT = 3.6V VBAT = 3.9V 600 300 0 4.0 2000 1500 1000 VBAT = 2.7V VBAT = 3.3V VBAT = 3.6V VBAT = 3.9V 500 0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 Input Voltage (V) 3620.2009.12.1.3 4.0 4.5 5.0 5.5 6.0 6.5 Input Voltage (V) www.analogictech.com 7 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Functional Block Diagram PGND Reverse Blocking VPIN LX Reverse Blocking CS VCC Volt Det/ UVLO BAT EN PWM / Linear Charge Control GND VREF CHR TS Over-Temperature Protection ISET TERM Charge status STAT1 Current Set CT STAT2 Timer Functional Description Linear vs. Switching Battery Charging Control Loop The AAT3620 uses an average current mode step-down converter to implement the DC/DC switch-mode converter function during constant current mode charging. The technique of average current mode control overcomes peak current control problems by introducing a high gain integrating current error amplifier into the current loop. Average current tracks the sensed output current with a high degree of accuracy and the noise immunity is excellent. The oscillator saw-tooth ramp provides compensation so no slope compensation is required for duty cycle exceeding 50%. The high gain of the current error amplifier at DC accurately programs the output. The switching charger works in continuous current mode PWM only. There is a soft start before entering constant current charging mode and the charger re-enters linear operation in constant voltage mode when the charge current drops below 300mA. The AAT3620 performs battery charging using the benefits of the step-down or "buck" architecture to multiply the input current when stepping down the output voltage. This property is expressed mathematically in the comparison below, and provides the ability to maximize battery charging from current limited devices, as well as greatly decrease power and heat related dissipation. Linear Charging Linear charge current relationship*: IBATL = IIN Efficiency of linear charger: nL = VBAT VIN * Equation does not take into account thermal foldback. 8 www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Switch-Mode Charging Switch-mode current relationship: IBATS = nS * VIN * IIN VBAT Where nS =90%. Example: Power Savings Conventional Linear Charger IC: PD = (VIN - VBAT)*IBAT = (5-3.5)*0.5 = 0.75W Switch-Mode Charger IC: PD = VBAT*IBAT/ - VBAT*IBAT = 3.5*0.5/0.9-3.5*0.5 = 0.195W Adapter Input Charge Inhibit and Resume The AAT3620 has a UVLO and power on reset feature so that if the input supply to the ADP pin drops below the UVLO threshold, the charger will suspend charging and shut down. When power is re-applied to the IN pin or the UVLO condition recovers, the system charge control will assess the state of charge on the battery cell and will automatically resume charging in the appropriate mode for the condition of the battery. Input/Output Capacitor and Inductor The AAT3620 contains a high performance 2A, 1.5MHz synchronous step-down converter. The step-down converter operates to ensure high efficiency performance over all load conditions. It requires only 3 external power components (CIN, COUT, and L). Apart from the input capacitor, only a small L-C filter is required at the output side for the step-down converter to operate properly. Typically, a 4.7H inductor such as the Wurth 7447789004 and a 22F to 47F ceramic output capacitor is recommended for low output voltage ripple and small component size. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. A 22F ceramic input capacitor is sufficient for most applications. Battery Charging Battery charging starts only after the AAT3620 checks several conditions in order to maintain a safe charging environment. The input supply must be above the minimum operating voltage (UVLO) and above the battery voltage by 0.3V, the battery temperature must be within 3620.2009.12.1.3 the 0C ~ 45C range, and the enable pin must be high. The AAT3620 checks the condition of the battery and determines which charging mode to apply. If the battery voltage is below VBAT_BC, the AAT3620 begins battery conditioning until the battery voltage reaches VBAT_BC. The battery conditioning current is 10% of constant current level. At this point the AAT3620 begins constant current mode charging. The constant current mode current level is programmed using a single resistor from the ISET pin to ground. Programmed current can be set from a minimum of 1A to a maximum of 2.0A. Constant current charging will continue until the battery voltage reaches the voltage regulation point VBAT_REG. When the battery voltage reaches VBAT_REG, the AAT3620 will transition to constant-voltage mode. The regulation voltage is factory programmed to a nominal 4.2V and will continue charging until the charging current has reduced to the termination current programmed by the resistor connected from ITERM to ground. The termination current program range is from 50mA to 200mA. After the charge cycle is complete, the AAT3620, turns off the series pass device and automatically goes into a power saving sleep mode. During this time the series pass device will block current in both directions therefore preventing the battery from discharging through the IC. The AAT3620 will remain in sleep mode, even if the charger source is disconnected, until either the battery terminal voltage drops below the VBAT_RCH threshold, the charger EN pin is recycled, or the charging source is reconnected. In all cases the AAT3620 will monitor all parameters and resume charging in the most appropriate mode. Figure 1 illustrates the entire battery charging profile, which consists of three phases. 1. 2. 3. Preconditioning-Current Mode (Trickle) Charge Constant-Current Mode Charge Constant-Voltage Mode Charge The battery preconditioning current is equal to 10% of the constant current charging level, so the battery preconditioning current set range is 100mA to 200mA. Linear mode is on standby while switch-mode is active in the constant current charging region 2.6V < VBAT < 4.2V. The charger will re-enter linear mode while in constant voltage mode after the switch-mode current drops below 300mA. The termination current is programmed by an external resistor with a separate ITERM pin and the termination current set pin also monitors the charge current. The output short circuit current is equal to the battery preconditioning current. www.analogictech.com 9 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger V Preconditioning Trickle Constant Current Constant Voltage Charge Complete Charge Fast Charge Phase Taper Charge Phase Regulated Voltage Phase 4.2 1 3 2 Constant Current Charge Phase Battery Discharge Constant Voltage Taper Charge Phase Battery Recharge Voltage Threshold 2 3 I Regulated Current 1C Constant Current Mode Voltage Threshold 2.6 300mA Trickle Charge and Termination Threshold (Programmable) 0.1C Regulated Current L S S L L Figure 1: Current vs. Voltage and Charger Time Li-ion Battery Charging and Recharge Profile. The profile consists of three phases: 1. Preconditioning-Current Mode (Trickle) Charge - Linear Mode 2. Constant-Current (Fast) Mode Charge - Switching Mode 3. Constant-Voltage Mode (Taper) Charge - Switching/Linear Mode. Preconditioning Trickle Charge Constant-Current Mode Charge Current Battery charging commences only after the AAT3620 battery charger checks several conditions in order to maintain a safe charging environment. The System operation flow chart for the battery charger operation is shown in Figure 4. The input supply must be above the minimum operating voltage (UVLO) and the enable pin (EN) must be high (it is internally pulled up). When the battery is connected to the BAT pin, the battery charger checks the condition of the battery and determines which charging mode to apply. Trickle charge continues until the battery voltage reaches VBAT_BC. At this point the battery charger begins constant-current charging. The current level default for this mode is programmed using a resistor from the ISET pin to ground. Programmed current can be set at a minimum of 100mA and up to a maximum of 2.0A. Preconditioning-Current Mode Charge Current Constant-Voltage Mode Charge If the battery voltage is below the Preconditioning Voltage Threshold VCH_BC, the battery charger initiates precondition trickle charge mode and charges the battery at 10% of the programmed constant-current magnitude. For example, if the programmed current is 1A, the trickle charge current will be 100mA. Trickle charge is a safety precaution for a deeply discharged cell. It also reduces the power dissipation in the internal series pass MOSFET when the input-output voltage differential is at its highest. 10 The AAT3620 contains a high performance 2A, 1.5MHz synchronous step-down converter. The step-down converter operates to ensure high efficiency performance over all load conditions. It requires only 3 external power components (CIN, COUT, and L). Constant current charging will continue until the battery voltage reaches the Output charge voltage regulation point VBAT_REG. When the battery voltage reaches VBAT_REG, the battery charger transitions to constant-voltage mode. VBAT_REG is factory programmed to 4.2V (nominal). Charging in constant-voltage mode will continue until the charge current has reduced to the programmed end of charge termination current. www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger System Operation Flowchart Enable No Power On Reset Yes No Power Input Voltage VIN > VUVLO VIN : VPIN, VCC Expired Yes Shut Down Yes Fault Conditions Monitoring OV, OT, VTS1 < TS < V TS2 Charge Timer Control No Preconditioning Test VBAT < VBAT_BC Yes Preconditioning (Trickle Charge) VBAT > VBAT_BC No No Recharge Test VBAT_RCH > VBAT Yes Current Phase Test VBAT < VBAT_EOC Yes Constant Current Charge Mode VBAT > VBAT_EOC No Voltage Phase Test IBAT > ITERM Yes Constant Voltage Charge Mode IBAT < ITERM No Charge Completed Figure 2: System Operation Flowchart for the Battery Charger. 3620.2009.12.1.3 www.analogictech.com 11 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Power Saving Mode The battery charger will remain in sleep mode even if the charger source is disconnected. It will come out of sleep mode if either the battery terminal voltage drops below the VBAT_RCH threshold, the charger EN pin is recycled, or the charging source is reconnected. In all cases, the battery charger will monitor all parameters and resume charging in the most appropriate mode. Programming Charge Current (ISET) The default constant current mode charge level is user programmed with a set resistor placed between the ISET pin and ground. The accuracy of the constant charge current, as well as the preconditioning trickle charge current, is dominated by the tolerance of the set resistor. For this reason, a 1% tolerance metal film resistor is recommended for the set resistor function. The constant charge current levels from 1A to 2A may be set by selecting the appropriate resistor value from Table 1 and Figure 3. Constant Charging Current ICH_CC (mA) Set Resistor Value (k) 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 50 55 60 65 70 75 80 85 90 95 100 Table 1: Constant Current Charge vs. ISET Resistor Value. Constant-Current Charge Mode Current vs. ISET Resistor (VIN = 5V; VBAT = 3.5V) Fast Charge Current (mA) After the charge cycle is complete, the battery charger turns off the series pass device and automatically goes into a power saving sleep mode. During this time, the series pass device will block current in both directions to prevent the battery from discharging through the battery charger. 2000 1800 1600 1400 1200 1000 800 600 400 20 30 40 50 60 70 80 90 100 ) ISET Resistor (K Figure 3: Constant-Current Mode Charge ICH_CC Setting vs. ISET Resistor. Programmable Charge Termination Current The charge termination current ITERM can be programmed by connecting a resistor from TERM to GND: ITERM = RTERM * 10-6 If the TERM pin is left open, the termination current will set to 200mA as the default value. When the charge current drops to the defaulted 10% of the programmed charge current level or programmed terminated current in the constant voltage mode, the device terminates charging and goes into a sleep state. The charger will remain in this sleep state until the battery voltage decreases to a level below the battery recharge voltage threshold (VBAT_RCH). Consuming very low current in sleep state, the AAT3620 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 AAT3620 input voltage drops, the device will enter sleep state and automatically resume charging once the input supply has recovered from the fault condition. The TERM pin can also be used as a charge current monitor based on the following equation: Charge Current Voltage Level = 1A/V 12 www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Status Indicator (STAT1/2) Charge Status Output The AAT3620 provides battery charge status via two status pins (STAT1 and STAT2). Each of the two pins is internally connected to an N-channel open drain MOSFET. The status pins can indicate the following conditions: Option 1: Default Option STAT1 Pre-Charge Fast-Charge End of Charge (Charge Complete) Charge Disabled Sleep Mode No Battery (with Charge Enabled) Fault Condition (Battery 0V) Fault Condition (Battery OT/UT) Fault Condition (Device OT) Fault (Time Out) TERM (Current reached in CVM) ON ON OFF OFF OFF OFF OFF OFF OFF OFF Option 2 STAT1 Pre-Charge Fast-Charge End of Charge (Charge Complete) Charge Disabled Sleep Mode No Battery (with Charge Enabled) Fault Condition (Battery 0V) Fault Condition (Battery OT/UT) Fault Condition (Device OT) Fault (Time Out) TERM (Current reached in CVM) ON ON OFF OFF OFF STAT1 (50% Duty Cycle) STAT2 STAT2 (50% Duty Cycle) ON OFF ON OFF OFF ON ON OFF OFF OFF OFF OFF STAT1 (50%) STAT2 ON OFF OFF OFF OFF OFF OFF ON ON ON ON OFF OFF ON ON OFF OFF STAT2 (50%) Table 2: Constant Current Charge vs. ISET Resistor Value. The LEDs should be biased with as little current as necessary to create reasonable illumination; therefore, a ballast resistor should be placed between the LED cathode and the STAT pins. LED current consumption will add to the overall thermal power budget for the device package, hence it is good to keep the LED drive current to a minimum. 2mA should be sufficient to drive most low cost green or red LEDs. It is not recommended to exceed 8mA for driving an individual status LED. The required ballast resistor values can be estimated using the following formula: RBALLAST = (VIN - VF(LED)) ILED Example: RBALLAST = 3620.2009.12.1.3 (5.0V - 2.0V) = 1.5k 2mA Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA. Protection Circuitry Charge Safety Timer (CT) While monitoring the charge cycle, the AAT3620 utilizes a charge safety timer to help identify damaged cells and to ensure that the cell is charged safely. Operation is as follows: upon initiating a charging cycle, the AAT3620 charges the cell at 10% of the programmed maximum charge until VBAT > 2.6V. If the cell voltage fails to the precondition threshold of 2.6V (typ) before the safety timer expires, the cell is assumed to be damaged and the charge cycle terminates. If the cell voltage exceeds 2.6V prior to the expiration of the timer, the charge cycle proceeds into fast charge. Three timeout periods of 25 minutes for Trickle Charge mode, 2 hours for Constant Current Mode and 3 hours for Constant Voltage mode. www.analogictech.com 13 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Mode Time Trickle Charge (TC) Time Out Trickle Charge (TC) + Constant Current (CC) Mode Time Out Constant Voltage (VC) Mode Time Out 25 minutes 2 hours 3 hours Table 3: Summary for a 0.1F Ceramic Capacitor Used for the Timing Capacitor. The AAT3620 has a battery fault detector, which, when used in conjunction with a 0.1F capacitor on the CT pin, outputs a 1Hz signal with 50% duty cycle at the STAT1 pin in the event of a timeout while in the trickle charge mode. The CT pin is driven by a constant current source and will provide a linear response to increases in the timing capacitor value. Thus, if the timing capacitor were to be doubled from the nominal 0.1F value, the time-out periods would be doubled. If the programmable watchdog timer function is not needed, it can be disabled by terminating the CT pin to ground. The CT pin should not be left floating or unterminated, as this will cause errors in the internal timing control circuit. The constant current provided to charge the timing capacitor is very small, and this pin is susceptible to noise and changes in capacitance value. Therefore, the timing capacitor should be physically located on the printed circuit board layout as close as possible to the CT pin. Since the accuracy of the internal timer is dominated by the capacitance value, a 10% tolerance or better ceramic capacitor is recommended. Ceramic capacitor materials, such as X7R and X5R types, are a good choice for this application. Battery Temperature Fault Monitoring (TS) In the event of a battery over-temperature condition, the charge control will turn off the internal pass device and report a battery temperature fault on the STAT pins. After the system recovers from a temperature fault, the device will resume charging operation. The AAT3620 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. The internal battery temperature sensing system (Figure 3) is comprised of two comparators which establish a voltage window for safe operation. The thresholds for the TS operating window are bounded by the VTS1 and VTS2 specifications. Referring to the electrical characteristics table in this datasheet, the VTS1 threshold = 0.30 * VIN and the VTS2 threshold = 0.60 * VIN. An external resistor RT with a value equal to the NTC thermistor resistance must be connected between TS and VIN. This system is intended for use with negative temperature coefficient thermistors (NTC) which are typically integrated into the battery package. Most of the commonly used NTC thermistors in battery packs are approximately 10k at room temperature (25C). If the battery becomes too hot during charging due to an internal fault or excessive constant charge current, the thermistor will heat up and reduce in value, pulling the TS pin voltage lower than the TS1 threshold, and the AAT3620 will stop charging until the condition is removed, when charging will be resumed. If the use of the TS pin function is not required by the system, it should be tied to VPIN using a 10k resistor. VIN Over-Voltage Protection An over-voltage event is defined as a condition where the voltage on the BAT pin exceeds the maximum battery charge voltage and is set by the over-voltage protection threshold (VBAT_OVP). If an over-voltage condition occurs, the AAT3620 charge control will shut down the device until the voltage on the BAT pin drops below VBAT_OVP. The AAT3620 will resume normal charging operation after the over-voltage condition is removed. During an over-voltage event, the STAT LEDs will report a system fault. VPIN 0.60x VIN Battery Pack Battery Hot Fault Over-Temperature Shutdown x V IN The AAT3620 has a thermal protection control circuit which will shut down charging functions should the internal die temperature exceed the preset thermal limit threshold. Once the internal die temperature falls below the thermal limit, normal operation will resume the previous charging state. 14 Battery Cold Fault TS Figure 3: AAT3620 Battery Temperature Sense Circuit. www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Thermal Considerations The actual maximum charging current is a function of Charge Adapter input voltage, the state of charge of the battery at the moment of charge, the system supply current from the BAT pin, the ambient temperature and the thermal impedance of the package. The maximum programmable current may not be achievable under all operating parameters. The AAT3620 is offered in a TDFN33-14 package which can provide up to 2W of power dissipation when it is properly bonded to a printed circuit board and has a maximum thermal resistance of 50C/W. Many considerations should be taken into account when designing the printed circuit board layout, as well as the placement of the charger IC package in proximity to other heat generating devices in a given application design. The ambient temperature around the charger IC will also have an effect on the thermal limits of a battery charging application. The maximum limits that can be expected for a given ambient condition can be estimated by the following discussion. First, the maximum power dissipation for a given situation should be calculated: IQOP = Quiescent Current Consumed by the IC for Normal Operation [5mA] RDS(ON)HS and RDS(ON)LS = On-resistance of step-down high and low side MOSFETs The power dissipation for the linear charging mode can be calculated by the following equation: PD(MAX) = [(VPIN - VBAT) * ICH_BC + (VPIN * IQOP)] Where: PD(MAX) = Total Power Dissipation by the Device VPIN = Input Voltage VBAT = Battery Voltage as Seen at the BAT Pin ICH_BC = Battery Conditioning Charge Current Programmed for the Application IQOP = Quiescent Current Consumed by the Charger IC for Normal Operation [5mA] By substitution, we can derive the maximum charge current before reaching the thermal limit condition (thermal loop). The maximum charge current is the key factor when designing battery charger applications. (TJ(MAX) - TA) PD(MAX) = JA ICH_BC(MAX) = Where: PD(MAX) = Maximum Power Dissipation (W) JA = Package Thermal Resistance (C/W) TJ(MAX) = Maximum Device Thermal Shutdown Temperature (C) [140C] TA = Ambient Temperature (C) The power dissipation for both the linear charging mode and the switching charger mode should be considered. The power dissipation for the switching charger can be calculated by the following equation: PD(MAX) = ICH_CC2 * [RDSONHS * VBAT + RDSONLS * (VPIN - VBAT)] VPIN + [(tSW * fSW * ICH_CC + IqOP) * VPIN] Where: PD(MAX) = Total Power Dissipation by the Device VPIN = Adapter Input Voltage VBAT = Battery Voltage at the BAT Pin ICH_CC = Constant Charge Current Programmed for the Application 3620.2009.12.1.3 (PD(MAX) - TA * IQOP) VPIN - VBAT (TJ - TA) JA - VIN - IOP ICH(MAX) = VIN - VBAT In general, the worst condition is the greatest voltage drop across the charger IC, when battery voltage is charged up to the preconditioning voltage threshold and entering Constant Current switching charge mode. Example Worst Case Power Dissipation The worst case power dissipation can be calculated using the lowest battery voltage level when the charger enters CC charge mode and the charge current is set to 2A. ICH_CC = 2A VPIN =6V RDSONHS = 0.3 RDSONLS = 0.25 tSW = 5 * 10-9 IQOP = 0.005A fSW = 1.5 * 106 TA = 85C JA = 50C/W www.analogictech.com 15 PRODUCT DATASHEET AAT3620 BatteryManagerTM PD(MAX) = 1-Cell Li+ Switch Mode Battery Charger following layout guidelines should be followed to ensure proper operation of the AAT3620: (2A)2 * [0.3 * 2.8V + 0.25 * (6V - 2.8V)] 6V 1. + [(5 * 10-9 * [1.5 * 106]* 2A + 0.005A) * 6V] PD(MAX) = 1.213W TJ(MAX) = 85 + 50 * 1.213 TJ(MAX) = 145.65 2. For the Linear Mode: IQOP = 0.005A VPIN = 6V VBAT = 2V ICH_BC = 0.2A 3. PD(MAX) = [(6V - 2V) * 0.2A + (6V * 0.005A)] 4. PD(MAX) = 0.83W 5. Layout Guidance Figure 5 is the evaluation board schematic. The evaluation board has additional components for easy evaluation; the actual bill of materials required for the system is shown in Table 4. When laying out the PC board, the C6 22F The exposed pad EP must be reliably soldered to PGND/AGND and multilayer GND. The exposed thermal pad should be connected to board ground plane and pins 2 and 3. The ground plane should include a large exposed copper pad under the package with vias to all board layers for thermal dissipation. The power traces, including GND traces, the LX traces and the VIN trace should be kept short, direct and wide to allow large current flow. The L1 connection to the LX pins should be as short as possible. Use several via pads when routing between layers. The input capacitors (C1, C5, C6, and C7) should be connected as close as possible to VPIN (Pin 1) VCC (Pin 4) and GND/PGND (Pin 2,3) to get good power filtering. The output capacitors C2, C4, and C9 and inductor L1 should be connected as close as possible and there should not be any signal lines under the inductor. The resistance of the trace from the load return to the PGND (Pin 2) should be kept to a minimum. This will help to minimize any error in DC regulation due to differences in the potential of the internal signal ground and the power ground. C1 0.1F TP5 CS GND TB2 100 TP2 R7 VIN L1 4.7H VCC TP1 1 VIN C7 100F (Optional) TP3 GND VIN AAT3620-TDFN33-14 JP3 (open) C5 10F 2 3 4 JP1 5 R4 EN 100k C3 0.1F 6 7 VPIN LX PGND CS GND BAT VCC TS EN TERM ISET STAT1 CT EP STAT2 TP4 14 TP8 R1 10k BAT LX 13 12 C2 C4 11 10 9 8 22F R3 47F TB1 BAT GND TS 49.9k TS R5 2k U1 D1 JP2 TS VIN R6 STAT1 D2 2k STAT2 R2 10k TP7 TP6 GND Figure 5: AAT3620 2A Evaluation Kit Schematic. 16 www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Quantity Value Designator Footprint Description 1 2 2 1 (Optional) 1 1 2 2 1 1 1 2 10F 0.1F 22F 100F 47F 4.7H 10K 2k 49.9k 100k 100 LED C5 C1, C3 C2, C6 C10 C4 L1 R1, R2 R5, R6 R3 R4 R7 D1, D2 0603 0402 1206 C 1206 7mm x 7mm 0402 0402 0402 0402 0402 0402 Capacitor, Ceramic, X5R, 10V, 20% Capacitor, Ceramic, 20%, 10V, X5R Capacitor, Ceramic, 20%, 10V, X5R Capacitor, Tantalum, 16V, 10% Capacitor, Ceramic, 20%, 10V, X5R Inductor, Wurth, 7447789004 Resistor, 5% Resistor, 5% Resistor, 1% Resistor, 1% Resistor, 1% Red and Green SMD Table 4: Minimum AAT3620 Bill of Materials. Figure 6: AAT3620 Evaluation Kit Top Layer. 3620.2009.12.1.3 Figure 7: AAT3620 Evaluation Kit Bottom Layer. www.analogictech.com 17 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Ordering Information Package Part Marking1 Part Number (Tape and Reel)2 TDFN33-14 6WXYY AAT3620IWO-4.2-T1 All AnalogicTech products are offered in Pb-free packaging. The term "Pb-free" means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/aboutus/quality.php. Packaging Information TDFN33-14 Detail "A" 3.000 0.050 2.500 0.050 Index Area 3.000 0.050 1.650 0.050 Top View Bottom View + 0.100 - 0.000 Pin 1 Indicator (Optional) 0.180 0.050 Side View 0.400 BSC 0.000 0.203 REF 0.750 0.050 0.425 0.050 Detail "A" 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. 18 www.analogictech.com 3620.2009.12.1.3 PRODUCT DATASHEET AAT3620 BatteryManagerTM 1-Cell Li+ Switch Mode Battery Charger Advanced Analogic Technologies, Inc. 3230 Scott Boulevard, Santa Clara, CA 95054 Phone (408) 737-4600 Fax (408) 737-4611 (c) Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech's terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders. 3620.2009.12.1.3 www.analogictech.com 19