AAT2556 Battery Charger and Step-Down Converter for Portable Applications General Description Features The AAT2556 is a member of AnalogicTech's Total Power Management IC™ (TPMIC™) product family. It is a fully integrated 500mA battery charger plus a 250mA step-down converter. The input voltage range is 4V to 6.5V for the battery charger and 2.7V to 5.5V for the step-down converter, making it ideal for single-cell lithium-ion/polymer batterypowered applications. • • The battery charger is a complete constant current/ constant voltage linear charger. It offers an integrated pass device, reverse blocking protection, high current accuracy and voltage regulation, charge status, and charge termination. The charging current is programmable via external resistor from 15mA to 500mA. In addition to standard features, the device offers over-voltage, current limit, and thermal protection. • • • The step-down converter is a highly integrated converter operating at 1.5MHz of switching frequency, minimizing the size of external components while keeping switching losses low. It has independent input and enable pins. The output voltage ranges from 0.6V to the input voltage. The feedback and control deliver excellent load regulation and transient response with a small output inductor and capacitor. SystemPower™ Battery Charger: — Input Voltage Range: 4V to 6.5V — Programmable Charging Current up to 500mA — Highly Integrated Battery Charger — Charging Device — Reverse Blocking Diode Step-Down Converter: — Input Voltage Range: 2.7V to 5.5V — Output Voltage Range: 0.6V to VIN — 250mA Output Current — Up to 96% Efficiency — 30µA Quiescent Current — 1.5MHz Switching Frequency — 100µs Start-Up Time Short-Circuit, Over-Temperature, and Current Limit Protection TDFN33-12 Package -40°C to +85°C Temperature Range Applications • • • • • • The AAT2556 is available in a Pb-free, thermallyenhanced TDFN33-12 package and is rated over the -40°C to +85°C temperature range. Bluetooth™ Headsets Cellular Phones Handheld Instruments MP3 and Portable Music Players PDAs and Handheld Computers Portable Media Players Typical Application Adapter / USB Input VIN ADP EN_BUCK STAT BATT + VOUT BAT EN_BAT L= 3.3µH C LX RFB2 2556.2006.05.1.0 BATT - ISET FB RSET GND Battery Pack RFB1 COUT System Enable 1 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Pin Descriptions Pin # Symbol 1 FB 2, 8, 10 3 GND EN_BUCK 4 EN_BAT 5 ISET 6 7 9 11 BAT STAT ADP LX 12 EP VIN Function Feedback input. This pin must be connected directly to an external resistor divider. Nominal voltage is 0.6V. Ground. Enable pin for the step-down converter. When connected to logic low, the step-down converter is disabled and it consumes less than 1µA of current. When connected to logic high, it resumes normal operation. Enable pin for the battery charger. When internally pulled down, the battery charger is disabled and it consumes less than 1µA of current. When connected to logic high, it resumes normal operation. Charge current set point. Connect a resistor from this pin to ground. Refer to typical curves for resistor selection. Battery charging and sensing. Charge status input. Open drain status input. Input for USB/adapter charger. Output of the step-down converter. Connect the inductor to this pin. Internally, it is connected to the drain of both high- and low-side MOSFETs. Input voltage for the step-down converter. Exposed paddle (bottom): connect to ground directly beneath the package. Pin Configuration TDFN33-12 (Top View) FB GND EN_BUCK EN_BAT ISET BAT 2 1 12 2 11 3 10 4 9 5 8 6 7 VIN LX GND ADP GND STAT 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Absolute Maximum Ratings1 Symbol VIN VADP VLX VFB VEN VX TJ TLEAD Description Input Voltage to GND Adapter Voltage to GND LX to GND FB to GND EN_BAT and EN_BUCK to GND BAT, ISET and STAT to GND Operating Junction Temperature Range Maximum Soldering Temperature (at leads, 10 sec) Value Units 6.0 -0.3 to 7.5 -0.3 to VIN + 0.3 -0.3 to VIN + 0.3 -0.3 to 6.0 -0.3 to VADP + 0.3 -40 to 150 300 V V V V V V °C °C Value Units 2.0 50 W °C/W Thermal Information Symbol PD θJA Description Maximum Power Dissipation Thermal Resistance2 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. 2556.2006.05.1.0 3 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Electrical Characteristics1 VIN = 3.6V; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol Description Conditions Step-Down Converter VIN Input Voltage VUVLO UVLO Threshold VOUT Output Voltage Tolerance2 VOUT IQ ISHDN ILIM Output Voltage Range Quiescent Current Shutdown Current P-Channel Current Limit High-Side Switch On Resistance Low-Side Switch On Resistance LX Leakage Current Line Regulation Feedback Threshold Voltage Accuracy FB Leakage Current Oscillator Frequency RDS(ON)H RDS(ON)L ILXLEAK ΔVLinereg/ΔVIN VFB IFB FOSC TS TSD THYS VEN(L) VEN(H) IEN Startup Time Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis Enable Threshold Low Enable Threshold High Input Low Current Min Typ 2.7 VIN Rising Hysteresis VIN Falling IOUT = 0 to 250mA, VIN = 2.7V to 5.5V Max Units 5.5 2.7 V V mV V % 200 1.8 -3.0 3.0 0.6 No Load EN = GND VIN 1.5 V µA µA mA Ω Ω µA %/V V µA MHz 100 µs 140 15 °C °C V V µA 30 1.0 600 0.59 0.42 VIN = 5.5V, VLX = 0 to VIN VIN = 2.7V to 5.5V VIN = 3.6V VOUT = 1.0V 1.0 0.597 From Enable to Output Regulation 0.2 0.606 0.615 0.2 0.6 VIN = VEN = 5.5V 1.4 -1.0 1.0 1. The AAT2556 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 2. Output voltage tolerance is independent of feedback resistor network accuracy. 4 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Electrical Characteristics1 VADP = 5V; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol Description Battery Charger Operation VADP Adapter Voltage Range Under-Voltage Lockout (UVLO) VUVLO UVLO Hysteresis IOP Operating Current ISHUTDOWN Shutdown Current ILEAKAGE Reverse Leakage Current from BAT Pin Voltage Regulation VBAT_EOC End of Charge Accuracy ΔVCH/VCH Output Charge Voltage Tolerance VMIN Preconditioning Voltage Threshold VRCH Battery Recharge Voltage Threshold Current Regulation ICH Charge Current Programmable Range ΔICH/ICH Charge Current Regulation Tolerance VSET ISET Pin Voltage KI_A Current Set Factor: ICH/ISET Charging Devices RDS(ON) Charging Transistor On Resistance Logic Control/Protection VEN(H) Input High Threshold VEN(L) Input Low Threshold VSTAT Output Low Voltage ISTAT STAT Pin Current Sink Capability VOVP Over-Voltage Protection Threshold ITK/ICHG Pre-Charge Current ITERM/ICHG Charge Termination Threshold Current Conditions Min Rising Edge 4.0 3 Typ 150 0.5 0.3 0.4 Charge Current = 200mA VBAT = 4.25V, EN = GND VBAT = 4V, ADP Pin Open 4.158 2.85 Measured from VBAT_EOC 4.20 0.5 3.0 -0.1 15 Max Units 6.5 4 V V mV mA µA µA 1 1 2 4.242 3.15 500 mA % V 1.1 Ω 10 2 800 VADP = 5.5V 0.9 1.6 0.4 0.4 8 STAT Pin Sinks 4mA ICH = 100mA 4.4 10 10 V % V V V V V mA V % % 1. The AAT2556 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -25°C to +85°C temperature range is guaranteed by design. 2556.2006.05.1.0 5 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Typical Characteristics – Step-Down Converter Efficiency vs. Load DC Load Regulation (VOUT = 1.8V; L = 3.3µH) 100 VIN = 2.7V VIN = 5.0V VIN = 3.6V Output Error (%) Efficiency (%) 90 (VOUT = 1.8V; L = 3.3µH) 1.0 80 VIN = 5.5V 70 60 VIN = 4.2V 50 40 0.1 1 10 100 0.5 VIN = 3.6V 0.0 VIN = 2.7V -0.5 1 Output Current (mA) (VOUT = 1.2V; L = 1.5µH) Output Error (%) VIN = 2.7V 90 VIN = 3.6V 70 60 VIN = 5.5V VIN = 5.0V 50 VIN = 4.2V 40 0.1 1 5.0 10 100 1000 1 10 100 Soft Start Line Regulation (VIN = 3.6V; VOUT = 1.8V; IOUT = 250mA; CFF = 100pF) (VOUT = 1.8V) 0.5 1.4 0.8 0.0 0.6 VO 0.4 0.2 -2.0 0.0 IL -0.2 -5.0 -0.4 Inductor Current (bottom) (A) 1.0 1.0 1000 0.6 1.6 2.0 -4.0 VIN = 3.6V VIN = 4.2V -0.5 Output Current (mA) 1.2 -3.0 0.0 Output Current (mA) 3.0 -1.0 VIN = 5.5V VIN = 2.7V VEN 4.0 VIN = 5.0V 0.5 -1.0 0.1 Accuracy (%) Efficiency (%) 1000 1.0 100 Enable and Output Voltage (top) (V) 100 DC Load Regulation (VOUT = 1.2V; L = 1.5µH) 30 10 Output Current (mA) Efficiency vs. Load 80 VIN = 5.0V VIN = 4.2V -1.0 0.1 1000 VIN = 5.5V IOUT = 0mA 0.4 0.3 IOUT = 50mA 0.2 IOUT = 150mA 0.1 0.0 -0.1 IOUT = 10mA IOUT = 250mA -0.2 -0.3 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Time (100µs/div) Input Voltage (V) 6 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Typical Characteristics – Step-Down Converter Output Voltage Error vs. Temperature Switching Frequency Variation vs. Temperature (VIN = 3.6V; VOUT = 1.8V; IOUT = 250mA) (VIN = 3.6V; VOUT = 1.8V) 3.0 2.0 8.0 Variation (%) Output Error (%) 10.0 1.0 0.0 -1.0 6.0 4.0 2.0 0.0 -2.0 -4.0 -6.0 -2.0 -8.0 -3.0 -40 -20 0 20 40 60 80 -10.0 100 -40 -20 0 Temperature (°°C) 20 40 60 80 100 Temperature (°°C) Frequency Variation vs. Input Voltage No Load Quiescent Current vs. Input Voltage (VOUT = 1.8V) 50 1.0 Supply Current (µA) Frequency Variation (%) 2.0 0.0 -1.0 -2.0 -3.0 -4.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 85°C 35 30 25°C 25 -40°C 20 15 3.1 3.9 4.3 4.7 5.1 Input Voltage (V) P-Channel RDS(ON) vs. Input Voltage N-Channel RDS(ON) vs. Input Voltage 5.5 750 100°C 800 700 700 600 25°C 500 120°C 650 85°C RDS(ON)L (mΩ Ω) 120°C 85°C 550 500 450 25°C 350 3.0 3.5 4.0 4.5 Input Voltage (V) 2556.2006.05.1.0 5.0 5.5 6.0 100°C 600 400 400 2.5 3.5 Input Voltage (V) 900 RDS(ON)H (mΩ Ω) 40 10 2.7 5.5 1000 300 45 300 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Input Voltage (V) 7 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Typical Characteristics – Step-Down Converter Load Transient Response Load Transient Response (10mA to 250mA; VIN = 3.6V; VOUT = 1.8V; COUT = 4.7µF; CFF = 100pF) (10mA to 250mA; VIN = 3.6V; VOUT = 1.8V; COUT = 4.7µF) 1.7 IO 1.6 ILX 1.5 1.4 1.3 1.2 1.9 Output Voltage (top) (V) Output Voltage (top) (V) VO 1.8 2.0 1.8 1.4 1.6 0.8 1.4 0.4 ILX 0.0 1.2 -0.2 Line Response Output Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 1mA) 40 6.5 6.0 5.5 1.70 5.0 1.65 4.5 VIN 4.0 1.55 3.5 1.50 3.0 Time (25µs/div) 20 0 0.07 0.06 VO 0.05 -20 0.04 -40 0.03 -60 0.02 -80 -100 0.01 IL Inductor Current (bottom) (A) VO Output Voltage (AC Coupled) (top) (mV) 7.0 Input Voltage (bottom) (V) Output Voltage (top) (V) 0.2 1.3 Time (25µs/div) 1.75 1.60 0.6 IO 1.5 (VOUT = 1.8V @ 250mA; CFF = 100pF) 1.90 1.80 1.0 1.7 Time (25µs/div) 1.85 1.2 VO Load and Inductor Current (bottom) (200mA/div) 1.9 Load and Inductor Current (bottom) (200mA/div) 2.0 0.00 -120 -0.01 Time (2µs/div) Output Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 250mA) 20 0 0.8 0.7 VO 0.6 -20 0.5 -40 0.4 -60 0.3 -80 -100 0.2 IL Inductor Current (bottom) (A) Output Voltage (AC Coupled) (top) (V) 40 0.1 -120 0.0 Time (200ns/div) 8 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Typical Characteristics – Battery Charger Charging Current vs. Battery Voltage Constant Charging Current vs. Set Resistor Values (VADP = 5V) 600 1000 RSET = 3.24kΩ 100 ICH (mA) ICH (mA) 500 10 400 RSET = 5.62kΩ 300 RSET = 8.06kΩ 200 RSET = 16.2kΩ 100 1 1 10 100 0 2.7 1000 2.9 3.1 3.3 RSET = 31.6kΩ 3.5 3.7 3.9 4.1 4.3 VBAT (V) RSET (kΩ Ω) End of Charge Battery Voltage vs. Supply Voltage End of Charge Voltage Regulation vs. Temperature (RSET = 8.06kΩ Ω) 4.206 4.23 RSET = 8.06kΩ 4.22 VBAT_EOC (V) VBAT_EOC (V) 4.204 4.202 4.200 RSET = 31.6kΩ 4.198 4.196 4.194 4.21 4.20 4.19 4.18 4.5 4.75 5 5.25 5.5 5.75 6 6.25 4.17 6.5 -50 -25 Constant Charging Current vs. Supply Voltage 50 75 100 (RSET = 8.06kΩ Ω) 210 220 208 210 205 VBAT = 3.3V ICH (mA) ICH (mA) 25 Constant Charging Current vs. Temperature (RSET = 8.06kΩ Ω) 200 190 VBAT = 3.6V VBAT = 4V 203 200 198 195 180 170 0 Temperature (°C) VADP (V) 193 4 4.25 4.5 4.75 5 5.25 5.5 VADP (V) 2556.2006.05.1.0 5.75 6 6.25 6.5 190 -50 -25 0 25 50 75 100 Temperature (°C) 9 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Typical Characteristics – Battery Charger Operating Current vs. Temperature Preconditioning Threshold Voltage vs. Temperature (RSET = 8.06kΩ Ω) (RSET = 8.06kΩ Ω) 550 3.03 3.02 450 VMIN (V) IOP (µA) 500 400 3.01 3 2.99 350 2.98 300 -50 -25 0 25 50 75 2.97 -50 100 -25 0 Temperature (°C) (RSET = 8.06kΩ Ω) ITRICKLE (mA) ITRICKLE (mA) 20.4 20.2 20.0 19.8 19.6 25 50 75 RSET = 5.62kΩ 30 RSET = 8.06kΩ 20 0 100 4 4.2 4.4 4.6 5 5.2 5.4 5.6 5.8 6 6.2 6.4 Recharging Threshold Voltage vs. Temperature Sleep Mode Current vs. Supply Voltage (RSET = 8.06kΩ Ω) 800 700 4.16 85°C 600 ISLEEP (nA) 4.14 4.12 4.10 4.08 500 400 300 4.06 200 4.04 100 -50 4.8 VADP (V) 4.18 4.02 RSET = 31.6kΩ RSET = 16.2kΩ Temperature (°C) (RSET = 8.06kΩ Ω) VRCH (V) 40 10 19.4 -25 0 25 50 Temperature (°C) 10 RSET = 3.24kΩ 50 0 100 60 20.6 -25 75 Preconditioning Charge Current vs. Supply Voltage 20.8 -50 50 Temperature (°C) Preconditioning Charge Current vs. Temperature 19.2 25 75 100 25°C -40°C 0 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 VADP (V) 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Typical Characteristics – Battery Charger VEN(H) vs. Supply Voltage VEN(L) vs. Supply Voltage (RSET = 8.06kΩ Ω) (RSET = 8.06kΩ Ω) 1.2 1.1 -40°C 1 -40°C VEN(L) (V) VEN(H) (V) 1.1 1 0.9 25°C 0.8 85°C 0.9 0.8 25°C 0.7 85°C 0.6 0.7 4 4.25 4.5 4.75 5 5.25 5.5 VADP (V) 2556.2006.05.1.0 5.75 6 6.25 6.5 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 VADP (V) 11 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Functional Block Diagram Reverse Blocking BAT ADP + Constant Current STAT OverTemperature Protection Charge Control + - ISET VREF EN_BAT UVLO VIN FB DH + LX Logic VREF DL EN_BUCK Input GND Functional Description The AAT2556 is a high performance power system comprised of a 500mA lithium-ion/polymer battery charger and a 250mA step-down converter. The battery charger is designed for single-cell lithium-ion/polymer batteries using a constant current and constant voltage algorithm. The battery charger operates from the adapter/USB input voltage range from 4V to 6.5V. The adapter/USB charging current level can be programmed up to 500mA for rapid charging applications. A status monitor output pin is provided to indicate the battery charge state by directly driving one external LED. Internal device temperature and charging 12 state are fully monitored for fault conditions. In the event of an over-voltage or over-temperature failure, the device will automatically shut down, protecting the charging device, control system, and the battery under charge. Other features include an integrated reverse blocking diode and sense resistor. The step-down converter operates with an input voltage of 2.7V to 5.5V. The switching frequency is 1.5MHz, minimizing the size of the inductor. Under light load conditions, the device enters power-saving mode; the switching frequency is reduced, and the converter consumes 30µA of current, making it ideal for battery-operated applications. The output voltage is programmable from VIN to as low as 0.6V. 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Power devices are sized for 250mA current capability while maintaining over 90% efficiency at full load. Light load efficiency is maintained at greater than 80% down to 1mA of load current. A high-DC gain error amplifier with internal compensation controls the output. It provides excellent transient response and load/line regulation. Under-Voltage Lockout The AAT2556 has internal circuits for UVLO and power on reset features. If the ADP supply voltage drops below the UVLO threshold, the battery charger will suspend charging and shut down. When power is reapplied to the ADP pin or the UVLO condition recovers, the system charge control will automatically resume charging in the appropriate mode for the condition of the battery. If the input voltage of the step-down converter drops below UVLO, the internal circuit will shut down. Protection Circuitry Over-Voltage Protection An over-voltage protection event is defined as a condition where the voltage on the BAT pin exceeds the over-voltage protection threshold (VOVP). If this over-voltage condition occurs, the charger control circuitry will shut down the device. The charger will resume normal charging operation after the over-voltage condition is removed. Current Limit, Over-Temperature Protection For overload conditions, the peak input current is limited at the step-down converter. As load impedance decreases and the output voltage falls closer to zero, more power is dissipated internally, which causes the internal die temperature to rise. In this case, the thermal protection circuit completely disables switching, which protects the device from damage. The battery charger has a thermal protection circuit which will shut down charging functions when the internal die temperature exceeds the preset ther- 2556.2006.05.1.0 mal limit threshold. Once the internal die temperature falls below the thermal limit, normal charging operation will resume. Control Loop The AAT2556 contains a compact, current mode step-down DC/DC controller. The current through the P-channel MOSFET (high side) is sensed for current loop control, as well as short-circuit and overload protection. A fixed slope compensation signal is added to the sensed current to maintain stability for duty cycles greater than 50%. The peak current mode loop appears as a voltage-programmed current source in parallel with the output capacitor. The output of the voltage error amplifier programs the current mode loop for the necessary peak switch current to force a constant output voltage for all load and line conditions. Internal loop compensation terminates the transconductance voltage error amplifier output. The error amplifier reference is fixed at 0.6V. Battery Charging Operation Battery charging commences only after checking several conditions in order to maintain a safe charging environment. The input supply (ADP) must be above the minimum operating voltage (UVLO) and the enable pin must be high (internally pulled down). When the battery is connected to the BAT pin, the charger checks the condition of the battery and determines which charging mode to apply. If the battery voltage is below VMIN, the charger begins battery pre-conditioning by charging at 10% of the programmed constant current; e.g., if the programmed current is 150mA, then the pre-conditioning current (trickle charge) is 15mA. Pre-conditioning is purely a safety precaution for a deeply discharged cell and will also reduce the power dissipation in the internal series pass MOSFET when the input-output voltage differential is at its highest. 13 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Charge Complete Voltage Preconditioning Trickle Charge Phase Constant Current Charge Phase Constant Voltage Charge Phase I = Max CC Regulated Current Constant Current Mode Voltage Threshold Trickle Charge and Termination Threshold I = CC / 10 Figure 1: Current vs. Voltage Profile During Charging Phases. Pre-conditioning continues until the battery voltage reaches VMIN. At this point, the charger begins constant-current charging. The current level for this mode is programmed using a single resistor from the ISET pin to ground. Programmed current can be set from a minimum 15mA up to a maximum of 500mA. Constant current charging will continue until the battery voltage reaches the voltage regulation point, VBAT. When the battery voltage reaches VBAT, the battery charger begins constant voltage mode. The regulation voltage is factory programmed to a nominal 4.2V (±0.5%) and will continue charging until the charging current has reduced to 10% of the programmed current. 14 After the charge cycle is complete, the pass device turns off and the device automatically goes into a power-saving sleep mode. During this time, the series pass device will block current in both directions, preventing the battery from discharging through the IC. The battery charger will remain in sleep mode, even if the charger source is disconnected, until one of the following events occurs: the battery terminal voltage drops below the VRCH threshold; the charger EN pin is recycled; or the charging source is reconnected. In all cases, the charger will monitor all parameters and resume charging in the most appropriate mode. 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Battery Charging System Operation Flow Chart Enable No Power On Reset Yes Power Input Voltage VADP > VUVLO Yes Shut Down Yes Fault Conditions Monitoring OV, OT Charge Control No Preconditioning Test V MIN > VBAT Yes Preconditioning (Trickle Charge) Yes Constant Current Charge Mode Yes Constant Voltage Charge Mode No No Recharge Test V RCH > VBAT Yes Current Phase Test V ADP > VBAT No Voltage Phase Test IBAT > ITERM No Charge Completed 2556.2006.05.1.0 15 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Application Information Soft Start / Enable Normal ICHARGE (mA) Set Resistor Ω) Value R2 (kΩ 500 400 300 250 200 150 100 50 40 30 20 15 3.24 4.12 5.62 6.49 8.06 10.7 16.2 31.6 38.3 53.6 78.7 105 The EN_BAT pin is internally pulled down. When pulled to a logic high level, the battery charger is enabled. When left open or pulled to a logic low level, the battery charger is shut down and forced into the sleep state. Charging will be halted regardless of the battery voltage or charging state. When it is re-enabled, the charge control circuit will automatically reset and resume charging functions with the appropriate charging mode based on the battery charge state and measured cell voltage from the BAT pin. The step-down converter features a soft start that limits the inrush current and eliminates output voltage overshoot during startup. The circuit is designed to increase the inductor current limit in discrete steps when the input voltage or enable input is applied. Typical start up time is 100µs. Adapter or USB Power Input Constant current charge levels up to 500mA may be programmed by the user when powered from a sufficient input power source. The battery charger will operate from the adapter input over a 4.0V to 6.5V range. The constant current fast charge current for the adapter input is set by the RSET resistor connected between ISET and ground. Refer to Table 1 for recommended RSET values for a desired constant current charge level. Programming Charge Current The fast charge constant current charge level is user programmed with a set resistor placed between the ISET pin and ground. The accuracy of the fast charge, as well as the preconditioning trickle charge current, is dominated by the tolerance of the set resistor used. For this reason, a 1% tolerance metal film resistor is recommended for the set resistor function. Fast charge constant current levels from 15mA to 500mA may be set by selecting the appropriate resistor value from Table 1. 16 1000 ICH (mA) Pulling EN_BUCK to logic low forces the converter in a low power, non-switching state, and it consumes less than 1µA of quiescent current. Connecting it to logic high enables the converter and resumes normal operation. Table 1: RSET Values. 100 10 1 1 10 100 1000 RSET (kΩ Ω) Figure 2: Constant Charging Current vs. Set Resistor Values. Charge Status Output The AAT2556 provides battery charge status via a status pin. This pin is internally connected to an Nchannel open drain MOSFET, which can be used to drive an external LED. The status pin can indicate several conditions, as shown in Table 2. Event Description Status No battery charging activity Battery charging via adapter or USB port Charging completed OFF ON OFF Table 2: LED Status Indicator. 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications The LED 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 pin. 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 formulas: Where: PD(MAX) = Maximum Power Dissipation (W) θJA = Package Thermal Resistance (°C/W) TJ(MAX) = Maximum Device Junction Temperature (°C) [135°C] TA = Ambient Temperature (°C) Figure 3 shows the relationship of maximum power dissipation and ambient temperature of the AAT2556. 3000 (VADP - VF(LED)) R 1= ILED PD(MAX) (mW) 2500 Example: 2000 1500 1000 500 R1 = 0 (5.5V - 2.0V) = 1.75kΩ 2mA 0 The AAT2556 is offered in a TDFN33-12 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 50°C/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 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: PD(MAX) = 2556.2006.05.1.0 (TJ(MAX) - TA) θJA 40 60 80 100 120 TA (°°C) Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA. Thermal Considerations 20 Figure 3: Maximum Power Dissipation. Next, the power dissipation of the battery charger can be calculated by the following equation: PD = [(VADP - VBAT) · ICH + (VADP · IOP)] Where: PD = Total Power Dissipation by the Device VADP = ADP/USB Voltage VBAT = Battery Voltage as Seen at the BAT Pin ICH = Constant Charge Current Programmed for the Application IOP = Quiescent Current Consumed by the Charger IC for Normal Operation [0.5mA] By substitution, we can derive the maximum charge current before reaching the thermal limit condition (thermal cycling). The maximum charge current is the key factor when designing battery charger applications. 17 AAT2556 Battery Charger and Step-Down Converter for Portable Applications ICH(MAX) = IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load stepdown converter switching losses. (PD(MAX) - VIN · IOP) VIN - VBAT (TJ(MAX) - TA) - V · I IN OP θJA ICH(MAX) = VIN - VBAT For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: In general, the worst condition is the greatest voltage drop across the IC, when battery voltage is charged up to the preconditioning voltage threshold. Figure 4 shows the maximum charge current in different ambient temperatures. 500 ICC(MAX) (mA) 400 TA = 60°C 300 TA = 85°C Since RDS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. Given the total losses, the maximum junction temperature can be derived from the θJA for the TDFN33-12 package which is 50°C/W. 200 TJ(MAX) = PTOTAL · ΘJA + TAMB 100 0 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 6.75 VIN (V) Figure 4: Maximum Charging Current Before Thermal Cycling Becomes Active. There are three types of losses associated with the step-down converter: switching losses, conduction losses, and quiescent current losses. Conduction losses are associated with the RDS(ON) characteristics of the power output switching devices. Switching losses are dominated by the gate charge of the power output switching devices. At full load, assuming continuous conduction mode (CCM), a simplified form of the losses is given by: PTOTAL = IO2 · (RDSON(H) · VO + RDSON(L) · [VIN - VO]) VIN + (tsw · FS · IO + IQ) · VIN 18 PTOTAL = IO2 · RDSON(H) + IQ · VIN Capacitor Selection Battery Charger Input Capacitor (C1) In general, it is good design practice to place a decoupling capacitor between the ADP pin and GND. An input capacitor in the range of 1µF to 22µF 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 during device enable and when battery charging is initiated. If the adapter input 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 transient effects when the power supply is "hot plugged" in. Step-Down Converter Input Capacitor (C3) Select a 4.7µF to 10µF X7R or X5R ceramic capacitor for the input. To estimate the required input capacitor size, determine the acceptable input ripple level (VPP) and solve for CIN. The calculated value varies with input voltage and is a maximum when VIN is double the output voltage. 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications CIN = ceramic capacitors are ideal for this function. To minimize stray inductance, the capacitor should be placed as closely as possible to the IC. This keeps the high frequency content of the input current localized, minimizing EMI and input voltage ripple. VO ⎛ V ⎞ · 1- O VIN ⎝ VIN ⎠ ⎛ VPP ⎞ - ESR · FS ⎝ IO ⎠ The proper placement of the input capacitor (C3) can be seen in the evaluation board layout in Figure 6. VO ⎛ V ⎞ 1 · 1 - O = for VIN = 2 · VO VIN ⎝ VIN ⎠ 4 CIN(MIN) = 1 ⎛ VPP ⎞ - ESR · 4 · FS ⎝ IO ⎠ Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value. For example, the capacitance of a 10µF, 6.3V, X5R ceramic capacitor with 5.0V DC applied is actually about 6µF. The maximum input capacitor RMS current is: IRMS = IO · VO ⎛ V ⎞ · 1- O VIN ⎝ VIN ⎠ The input capacitor RMS ripple current varies with the input and output voltage and will always be less than or equal to half of the total DC load current. VO ⎛ V ⎞ · 1- O = VIN ⎝ VIN ⎠ D · (1 - D) = 0.52 = 1 2 for VIN = 2 · VO IRMS(MAX) = VO IO 2 ⎛ V ⎞ · 1- O The term VIN ⎝ VIN ⎠ appears in both the input voltage ripple and input capacitor RMS current equations and is a maximum when VO is twice VIN. This is why the input voltage ripple and the input capacitor RMS current ripple are a maximum at 50% duty cycle. The input capacitor provides a low impedance loop for the edges of pulsed current drawn by the stepdown converter. Low ESR/ESL X7R and X5R 2556.2006.05.1.0 A laboratory test set-up typically consists of two long wires running from the bench power supply to the evaluation board input voltage pins. The inductance of these wires, along with the low-ESR ceramic input capacitor, can create a high Q network that may affect converter performance. This problem often becomes apparent in the form of excessive ringing in the output voltage during load transients. Errors in the loop phase and gain measurements can also result. Since the inductance of a short PCB trace feeding the input voltage is significantly lower than the power leads from the bench power supply, most applications do not exhibit this problem. In applications where the input power source lead inductance cannot be reduced to a level that does not affect the converter performance, a high ESR tantalum or aluminum electrolytic capacitor should be placed in parallel with the low ESR, ESL bypass ceramic capacitor. This dampens the high Q network and stabilizes the system. Battery Charger Output Capacitor (C2) The AAT2556 only requires a 1µF ceramic capacitor on the BAT pin to maintain circuit stability. This value should be increased to 10µF or more if the battery connection is made any distance from the charger output. If the AAT2556 is to be used in applications where the battery can be removed from the charger, such as with desktop charging cradles, an output capacitor greater than 10µF may be required to prevent the device from cycling on and off when no battery is present. Step-Down Converter Output Capacitor (C4) The output capacitor limits the output ripple and provides holdup during large load transitions. A 4.7µF to 10µF X5R or X7R ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions and has the ESR and ESL characteristics necessary for low output ripple. For enhanced transient response and 19 AAT2556 Battery Charger and Step-Down Converter for Portable Applications low temperature operation applications, a 10µF (X5R, X7R) ceramic capacitor is recommended to stabilize extreme pulsed load conditions. The output voltage droop due to a load transient is dominated by the capacitance of the ceramic output capacitor. During a step increase in load current, the ceramic output capacitor alone supplies the load current until the loop responds. Within two or three switching cycles, the loop responds and the inductor current increases to match the load current demand. The relationship of the output voltage droop during the three switching cycles to the output capacitance can be estimated by: COUT = 3 · ΔILOAD VDROOP · FS Once the average inductor current increases to the DC load level, the output voltage recovers. The above equation establishes a limit on the minimum value for the output capacitor with respect to load transients. The internal voltage loop compensation also limits the minimum output capacitor value to 4.7µF. This is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. Increased output capacitance will reduce the crossover frequency with greater phase margin. The maximum output capacitor RMS ripple current is given by: IRMS(MAX) = 1 2· 3 · VOUT · (VIN(MAX) - VOUT) L · FS · VIN(MAX) Dissipation due to the RMS current in the ceramic output capacitor ESR is typically minimal, resulting in less than a few degrees rise in hotspot temperature. Inductor Selection The step-down converter uses peak current mode control with slope compensation to maintain stability for duty cycles greater than 50%. The output inductor value must be selected so the inductor 20 current down slope meets the internal slope compensation requirements. The internal slope compensation for the AAT2556 is 0.45A/µsec. This equates to a slope compensation that is 75% of the inductor current down slope for a 1.8V output and 3.0µH inductor. m= L= 0.75 ⋅ VO 0.75 ⋅ 1.8V A = = 0.45 µsec L 3.0µH 0.75 ⋅ VO = m 0.75 ⋅ VO µsec ≈ 1.67 A ⋅ VO A 0.45A µsec For most designs, the step-down converter operates with an inductor value of 1µH to 4.7µH. Table 3 displays inductor values for the AAT2556 with different output voltage options. Manufacturer's specifications list both the inductor DC current rating, which is a thermal limitation, and the peak current rating, which is determined by the saturation characteristics. The inductor should not show any appreciable saturation under normal load conditions. Some inductors may meet the peak and average current ratings yet result in excessive losses due to a high DCR. Always consider the losses associated with the DCR and its effect on the total converter efficiency when selecting an inductor. The 3.0µH CDRH2D09 series inductor selected from Sumida has a 150mΩ DCR and a 470mA DC current rating. At full load, the inductor DC loss is 9.375mW which gives a 2.08% loss in efficiency for a 250mA, 1.8V output. Output Voltage (V) L1 (µH) 1.0 1.2 1.5 1.8 2.5 3.0 3.3 1.5 2.2 2.7 3.0/3.3 3.9/4.2 4.7 5.6 Table 3: Inductor Values. 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Adjustable Output Resistor Selection Resistors R3 and R4 of Figure 5 program the output to regulate at a voltage higher than 0.6V. To limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the suggested value for R4 is 59kΩ. Decreased resistor values are necessary to maintain noise immunity on the FB pin, resulting in increased quiescent current. Table 4 summarizes the resistor values for various output voltages. Ω R4 = 59kΩ Ω R4 = 221kΩ VOUT (V) Ω) R3 (kΩ Ω) R3 (kΩ 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.8 1.85 2.0 2.5 3.3 19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7 118 124 137 187 267 75 113 150 187 221 261 301 332 442 464 523 715 1000 ⎛ VOUT ⎞ ⎛ 3.3V ⎞ R3 = V -1 · R4 = 0.6V - 1 · 59kΩ = 267kΩ ⎝ REF ⎠ ⎝ ⎠ With enhanced transient response for extreme pulsed load application, an external feed-forward capacitor (C5 in Figure 5) can be added. Table 4: Adjustable Resistor Values For Step-Down Converter. JP4 BAT R4 59k 1 2 3 VIN R3 118k Buck Input ADP C3 4.7µF VOUT L1 C5 100pF C2 R2 1 2 3 4 5 6 U1 FB GND EN_BUCK EN_BAT ISET BAT 3.3µH VIN LX GND ADP GND STAT AAT2556 R1 2.2µF 8.06K 1K 1 2 3 JP3 C4 4.7µF 12 11 10 9 8 7 D1 JP1 0Ω C1 10µF RED LED 1 2 Enable_Buck JP2 Enable_Bat Figure 5: AAT2556 Evaluation Board Schematic. 2556.2006.05.1.0 21 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Printed Circuit Board Layout Considerations For the best results, it is recommended to physically place the battery pack as close as possible to the AAT2556 BAT pin. To minimize voltage drops on the PCB, keep the high current carrying traces adequately wide. Refer to the AAT2556 evaluation board for a good layout example (see Figures 6 and 7). The following guidelines should be used to help ensure a proper layout. 1. The input capacitors (C1, C3) should connect as closely as possible to ADP (Pin 9) and VIN (Pin 12). 2. C4 and L1 should be connected as closely as possible. The connection of L1 to the LX pin should be as short as possible. Do not make the node small by using narrow trace. The trace should be kept wide, direct, and short. Figure 6: AAT2556 Evaluation Board Top Side Layout. 22 3. The feedback pin (Pin 1) should be separate from any power trace and connect as closely as possible to the load point. Sensing along a highcurrent load trace will degrade DC load regulation. Feedback resistors should be placed as closely as possible to the FB pin (Pin 1) to minimize the length of the high impedance feedback trace. If possible, they should also be placed away from the LX (switching node) and inductor to improve noise immunity. 4. The resistance of the trace from the load return to PGND (Pin 10) and GND (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. 5. A high density, small footprint layout can be achieved using an inexpensive, miniature, nonshielded, high DCR inductor. Figure 7: AAT2556 Evaluation Board Bottom Side Layout. 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Component U1 C1 C2 C3, C4 C5 L1 R1 R2 R3 R4 JP1 JP2, JP3, JP4 D1 Part Number Description Manufacturer AAT2556IWP-T1 Battery Charger and Step-Down Converter for Portable Applications; TDFN33-12 Package CER 10µF 10V 20% X5R 0603 CER 2.2µF 6.3V 10% X7R 0603 CER 4.7µF 6.3V 10% X7R 0603 CER 100pF 50V 5% R2H 0603 Shielded SMD, 3.0µH, 150mΩ, 3x3x1mm 1KΩ, 5%, 1/4W; 0603 8.06KΩ, 1%, 1/4W; 0603 118KΩ, 1%, 1/4W; 0603 59KΩ, 1%, 1/4W; 0603 0Ω, 5%, 1/4W; 0603 Connecting Header, 2mm Zip Red LED; 1206 AnalogicTech ECJ-1VB0J106M GRM185B30J225KE25D GRM188R60J475KE19B GRM1886R1H101JZ01J CDRH2D09-3R0 Chip Resistor Chip Resistor Chip Resistor Chip Resistor Chip Resistor PRPN401PAEN CMD15-21SRC/TR8 Panasonic - ECG Murata Murata Murata Sumida Vishay Vishay Vishay Vishay Vishay Sullins Electronics Chicago Miniature Lamp Table 5: AAT2556 Evaluation Board Component Listing. 2556.2006.05.1.0 23 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Step-Down Converter Design Example Specifications VO = 1.8V @ 250mA, Pulsed Load ΔILOAD = 200mA VIN = 2.7V to 4.2V (3.6V nominal) FS = 1.5MHz TAMB = 85°C 1.8V Output Inductor L1 = 1.67 µsec µsec ⋅ VO2 = 1.67 ⋅ 1.8V = 3µH A A (use 3.0µH; see Table 3) For Sumida inductor CDRH2D09-3R0, 3.0µH, DCR = 150mΩ. ΔIL1 = ⎛ VO V ⎞ 1.8V 1.8V ⎞ ⎛ ⋅ 1- O = ⋅ 1= 228mA L1 ⋅ FS ⎝ VIN⎠ 3.0µH ⋅ 1.5MHz ⎝ 4.2V ⎠ IPKL1 = IO + ΔIL1 = 250mA + 114mA = 364mA 2 PL1 = IO2 ⋅ DCR = 250mA2 ⋅ 150mΩ = 9.375mW 1.8V Output Capacitor VDROOP = 0.1V COUT = 3 · ΔILOAD 3 · 0.2A = = 4µF; use 4.7µF 0.1V · 1.5MHz VDROOP · FS IRMS = (VO) · (VIN(MAX) - VO) 1 1.8V · (4.2V - 1.8V) · = 66mArms = 3.0µH · 1.5MHz · 4.2V · V L1 · F 2· 3 2· 3 S IN(MAX) 1 · Pesr = esr · IRMS2 = 5mΩ · (66mA)2 = 21.8µW 24 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Input Capacitor Input Ripple VPP = 25mV CIN = IRMS = ⎛ VPP ⎝ IO 1 1 = = 1.38µF; use 4.7µF ⎞ ⎛ 25mV ⎞ - 5mΩ · 4 · 1.5MHz - ESR · 4 · FS ⎠ ⎝ 0.2A ⎠ IO = 0.1Arms 2 P = esr · IRMS2 = 5mΩ · (0.1A)2 = 0.05mW AAT2556 Losses PTOTAL = IO2 · (RDSON(H) · VO + RDSON(L) · [VIN -VO]) VIN + (tsw · FS · IO + IQ) · VIN = 0.22 · (0.7Ω · 1.8V + 0.7Ω · [4.2V - 1.8V]) 4.2V + (5ns · 1.5MHz · 0.2A + 30µA) · 4.2V = 34.5mW TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (50°C/W) · 34.5mW = 86.7°C 2556.2006.05.1.0 25 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Output Voltage VOUT (V) Ω R4 = 59kΩ Ω) R3 (kΩ Ω1 R4 = 221kΩ Ω) R3 (kΩ L1 (µH) 0.62 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.8 1.85 2.0 2.5 3.3 — 19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7 118 124 137 187 267 — 75 113 150 187 221 261 301 332 442 464 523 715 1000 1.5 1.5 1.5 1.5 1.5 1.5 1.5 2.2 2.7 3.0/3.3 3.0/3.3 3.0/3.3 3.9/4.2 5.6 Table 6: Step-Down Converter Component Values. Manufacturer Sumida Sumida Sumida Sumida Sumida Sumida Sumida Sumida Sumida Sumida Sumida Taiyo Yuden Taiyo Yuden Taiyo Yuden Taiyo Yuden FDK FDK FDK FDK Part Number Inductance (µH) Max DC Current (mA) DCR Ω) (mΩ Size (mm) LxWxH Type CDRH2D09-1R5 CDRH2D09-2R2 CDRH2D09-2R5 CDRH2D09-3R0 CDRH2D09-3R9 CDRH2D09-4R7 CDRH2D09-5R6 CDRH2D11-1R5 CDRH2D11-2R2 CDRH2D11-3R3 CDRH2D11-4R7 NR3010 NR3010 NR3010 NR3010 MIPWT3226D-1R5 MIPWT3226D-2R2 MIPWT3226D-3R0 MIPWT3226D-4R2 1.5 2.2 2.5 3 3.9 4.7 5.6 1.5 2.2 3.3 4.7 1.5 2.2 3.3 4.7 1.5 2.2 3 4.2 730 600 530 470 450 410 370 900 780 600 500 1200 1100 870 750 1200 1100 1000 900 88 115 135 150 180 230 260 54 78 98 135 80 95 140 190 90 100 120 140 3.0x3.0x1.0 3.0x3.0x1.0 3.0x3.0x1.0 3.0x3.0x1.0 3.0x3.0x1.0 3.0x3.0x1.0 3.0x3.0x1.0 3.2x3.2x1.2 3.2x3.2x1.2 3.2x3.2x1.2 3.2x3.2x1.2 3.0x3.0x1.0 3.0x3.0x1.0 3.0x3.0x1.0 3.0x3.0x1.0 3.2x2.6x0.8 3.2x2.6x0.8 3.2x2.6x0.8 3.2x2.6x0.8 Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Chip shielded Chip shielded Chip shielded Chip shielded Table 7: Suggested Inductors and Suppliers. 1. For reduced quiescent current, R4 = 221kΩ. 2. R4 is opened, R3 is shorted. 26 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Manufacturer Murata Murata Part Number Value (µF) Voltage Rating Temp. Co. Case Size GRM118R60J475KE19B GRM188R60J106ME47D 4.7 10 6.3 6.3 X5R X5R 0603 0603 Table 8: Surface Mount Capacitors. 2556.2006.05.1.0 27 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN33-12 SPXYY AAT2556IWP-CA-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/pbfree. Legend Voltage Adjustable (0.6V) 0.9 1.2 1.5 1.8 1.9 2.5 2.6 2.7 2.8 2.85 2.9 3.0 3.3 4.2 Code A B E G I Y N O P Q R S T W C 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 28 2556.2006.05.1.0 AAT2556 Battery Charger and Step-Down Converter for Portable Applications Package Information TDFN33-12 2.40 ± 0.05 Detail "B" 3.00 ± 0.05 Index Area (D/2 x E/2) 0.3 ± 0.10 0.16 0.375 ± 0.125 0.075 ± 0.075 3.00 ± 0.05 1.70 ± 0.05 Top View Bottom View Pin 1 Indicator (optional) 0.23 ± 0.05 Detail "A" 0.45 ± 0.05 0.1 REF 0.05 ± 0.05 0.229 ± 0.051 + 0.05 0.8 -0.20 7.5° ± 7.5° Option A: C0.30 (4x) max Chamfered corner Side View Option B: R0.30 (4x) max Round corner Detail "B" Detail "A" All dimensions in millimeters © 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. Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. 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. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 2556.2006.05.1.0 29