PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications General Description Features The AAT2552 is a fully integrated 500mA battery charger, a 300mA step-down converter, and a 300mA low dropout (LDO) linear regulator. The input voltage range is 4V to 7.5V for the battery charger and 2.7V to 5.5V for the step-down converter and linear regulator, making it ideal for applications operating with single-cell lithiumion/polymer batteries. • Battery Charger: ▪ Input Voltage Range: 4V to 7.5V ▪ Programmable Charging Current up to 500mA ▪ Highly Integrated Battery Charger • Charging Device • Reverse Blocking Diode • Current Sensing • Step-Down Converter: ▪ Input Voltage Range: 2.7V to 5.5V ▪ Output Voltage Range: 0.6V to VIN ▪ 300mA Output Current ▪ Up to 96% Efficiency ▪ 45μA Quiescent Current ▪ 1.5MHz Switching Frequency ▪ 120μs Start-Up Time • Linear Regulator: ▪ 300mA Output Current ▪ Low Dropout: 400mV at 300mA ▪ Fast Line and Load Transient Response ▪ High Accuracy: ±1.5% ▪ 85μA Quiescent Current • Short-Circuit, Over-Temperature, and Current Limit Protection • TDFN34-16 Package • -40°C to +85°C Temperature Range The battery charger is a complete constant current/constant voltage linear charger. It offers an integrated pass device, reverse blocking protection, high accuracy current and voltage regulation, charge status, and charge termination. The charging current is programmable via external resistor from 30mA to 500mA. In addition to these standard features, the device offers over-voltage, current limit, and thermal protection. The step-down converter is a highly integrated converter operating at a 1.5MHz switching frequency, minimizing the size of external components while keeping switching losses low. The output voltage ranges from 0.6V to the input voltage. The AAT2552 linear regulator is designed for high speed turn-on and turn-off performance, fast transient response, and good power supply ripple rejection. Delivering up to 300mA of load current, it includes short-circuit protection and thermal shutdown. Applications The AAT2552 is available in a Pb-free, thermallyenhanced TDFN34-16 package and is rated over the -40°C to +85°C temperature range. • • • • • • • Bluetooth™ Headsets Cellular Phones GPS Handheld Instruments MP3 and Portable Music Players PDAs and Handheld Computers Portable Media Players Typical Application Adapter/USB Input Enable ADP INB STAT ENB INA EN_BAT ENA L1 VOUTB AAT2552 RFBB1 COUTB 4.7μF RFBB2 MODE FBB VOUTA RFBA1 FBA RFBA2 BATT+ BAT OUTA COUTA System LX C OUT ISET GND BATT- R SET Battery Pack 2552.2008.02.1.2 www.analogictech.com 1 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Pin Descriptions Pin # Symbol 1 EN_BAT 2 ISET 3 AGND 4 FBB 5 ENB 6 MODE 7 ENA 8 FBA 9 10 11 OUTA INA INB 12 LX 13 14 15 16 EP PGND BAT ADP STAT Function Enable pin for the battery charger. When connected to logic low, the battery charger is disabled and consumes less than 1μA of current. When connected to logic high, the charger operates normally (pulled down internally). Charge current set point. Connect a resistor from this pin to ground. Refer to typical characteristics curves for resistor selection. Analog ground. Feedback input for the step-down converter. This pin must be connected directly to an external resistor divider. Nominal voltage is 0.6V. Enable pin for the step-down converter. When connected to logic low, the step-down converter is disabled and consumes less than 1μA of current. When connected to logic high, the converter operates normally (pulled up internally). Pulled down internally for automatic PWM/LL operation. Connect to logic high for forced PWM. Drive with external clock signal to synchronize step-down converter to external clock in PWM mode. Enable pin for the linear regulator. When connected to logic low, the regulator is disabled and consumes less than 1μA of current. When connected to logic high, the LDO operates normally (pulled up internally). Feedback input for the LDO. This pin must be connected directly to an external resistor divider. Nominal voltage is 1.24V. Linear regulator output. Connect a 2.2μF capacitor from this pin to ground. Linear regulator input voltage. Connect a 1μF or greater capacitor from this pin to ground. Input voltage for the step-down converter. 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. Power ground. Battery charging and sensing. Connect to positive terminal of Lithium-ion/polymer battery. Input from USB port or AC wall adapter. Open drain status pin for charger. Exposed paddle (bottom): connect to ground directly beneath the package. Pin Configuration TDFN34-16 (Top View) EN_BAT ISET AGND FBB ENB MODE ENA FBA 2 1 16 2 15 3 14 4 13 5 12 6 11 7 10 8 9 STAT ADP BAT PGND LX INB INA OUTA www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Absolute Maximum Ratings1 Symbol Description VINA, VINB VADP VLX VFB VEN VX TJ TLEAD Input Voltage to GND Adapter Voltage to GND LX to GND FB to GND ENA, ENB, EN_BAT to GND BAT, ISET, STAT 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. 2552.2008.02.1.2 www.analogictech.com 3 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Electrical Characteristics1 VINB = 3.6V; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol Description Conditions Min Step-Down Converter Input Voltage VIN VUVLO 2.7 UVLO Threshold Output Voltage Tolerance2 VOUT Output Voltage Range VOUT Quiescent Current IQ Shutdown Current ISHDN P-Channel Current Limit ILIM High-Side Switch On Resistance RDS(ON)H RDS(ON)L Low-Side Switch On Resistance ILXLEAK LX Leakage Current ΔVOUT/ΔVOUT Load Regulation ΔVLinereg/ΔVIN Line Regulation Feedback Threshold Voltage Accuracy VFB FB Leakage Current IFB Oscillator Frequency FOSC Startup Time TS Over-Temperature Shutdown Threshold TSD Over-Temperature Shutdown Hysteresis THYS Enable Threshold Low VEN(L) Enable Threshold High VEN(H) Input Low Current IEN Linear Regulator VOUT VOUT VFB VIN VDO ΔVOUT/ VOUT*ΔVIN IOUT ISC IQ ISHDN Typ VINB Rising Hysteresis IOUTB = 0 to 300mA, VINB = 2.7V to 5.5V 45 VINB = 5.5V, VLX = 0 to VINB IOUTB = 0mA to 300mA VINB = 2.7V to 5.5V VINB = 3.6V VOUTB = 1.0V 0.591 0.4 0.1 0.6 0.609 0.2 1.5 120 140 15 0.6 1.4 -1.0 VINB = VENB = 5.5V TA = 25°C TA = -40°C to +85°C VINA = VOUTA + 1 to 5.0V Output Current Short-Circuit Current Quiescent Current Shutdown Current VOUTA > 2.0V VOUTA < 0.4V VINA = 5V; VENA = VIN VINA = 5V; VENA = 0V Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis Output Noise Output Voltage Temperature Coefficient Enable Threshold Low Enable Threshold High Enable Input Current 3.0 VINB 90 1.0 1.0 From Enable to Output Regulation Line Regulation TSD THYS eN TC VEN(L) VEN(H) IEN V V mV % V μA μA mA Ω Ω μA % %/V V μA MHz μs °C °C V V μA 0.3 0.5 IOUTA = 300mA; VOUT = 3.3V Power Supply Rejection Ratio 7.5 2.6 300 Output Voltage Range Feedback Voltage Accuracy Input Voltage Dropout Voltage4 PSRR Units 250 -3.0 0.6 No Load VENB = GND IOUTA = 1mA to 300mA Output Voltage Tolerance Max IOUTA =10mA -1.5 -2.5 1.2 1.22 VOUT + VDO3 1.0 1.24 400 1.5 2.5 3.3 1.26 5.5 650 V V V mV 0.09 %/V 150 1.0 mA mA μA μA 300 400 85 1kHz 10kHz 1MHz 70 50 30 140 15 95 8 eNBW = 100Hz to 100kHz dB 0.6 1.4 VINA = VENA = 5.5V % 1.0 °C °C μVRMS/√Hz ppm/°C V V μA 1. The AAT2552 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. 3. VDO is defined as VIN - VOUT when VOUT is 98% of nominal. 4. For VOUT <2.3V, VDO = 2.5V - VOUT. 4 www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Electrical Characteristics1 VADP = 5V; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol Description Conditions Battery Charger Operation Adapter Voltage Range VADP Under-Voltage Lockout (UVLO) VUVLO UVLO Hysteresis Operating Current IOP Shutdown Current ISHUTDOWN Reverse Leakage Current from BAT Pin ILEAKAGE Voltage Regulation End of Charge Accuracy VBAT_EOC Preconditioning Voltage Threshold VMIN Battery Recharge Voltage Threshold VRCH Current Regulation Charge Current Programmable Range ICH Charge Current Regulation Tolerance ΔICH/ICH ISET Pin Voltage VSET Current Set Factor: ICH/ISET KI_A Charging Devices Charging Transistor On Resistance RDS(ON) Logic Control/Protection VEN(H) Enable Threshold High Enable Threshold Low VEN(L) Output Low Voltage VSTAT STAT Pin Current Sink Capability ISTAT Over-Voltage Protection Threshold VOVP Pre-Charge Current ITK/ICHG Charge Termination Threshold Current ITERM/ICHG Rising Edge Min 4.0 3 150 0.5 0.3 0.4 Charge Current = 200mA VBAT = 4.25V, VEN_BAT = GND VBAT = 4V, ADP Pin Open 4.158 2.8 Measured from VBAT_EOC ICHARGE = 200mA Typ 4.20 3.0 -0.1 30 -10 Max Units 6.5 4 V V mV mA μA μA 1 1 2 4.242 3.2 V V V 500 10 mA % V 0.8 Ω 2 800 VADP = 5.5V 0.5 1.6 0.4 0.4 8 STAT Pin Sinks 4mA ICH = 100mA 4.4 10 10 V V V mA V % % 1. The AAT2552 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. 2552.2008.02.1.2 www.analogictech.com 5 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Typical Characteristics–Battery Charger Constant Charging Current vs. Set Resistors Operating Supply Current vs. RSET (VIN = 5.0V) (VIN = 5.0V) 10000 1000 1000 IOP (µA) ICH (mA) Constant Current Mode Preconditioning Mode 100 100 10 10 1 10 100 1000 1 10 Ω) RSET (kΩ 100 Ω) RSET (kΩ Operating Current vs. Temperature Sleep Mode Current vs. Input Voltage (VIN = 5.0V; RSET = 8.06kΩ Ω) (RSET = 8.06kΩ Ω) 540 800 700 520 ISLEEP (nA) IOP (µA) 500 480 25°C 85°C 600 500 400 300 200 460 -40°C 100 440 -50 -25 0 25 50 75 0 4.0 100 4.5 Temperature (°C) 5.0 5.5 6.0 6.5 Input Voltage (V) Battery Charging Current vs. Battery Voltage Constant Charging Current vs. Temperature (RSET = 8.06kΩ Ω) 600 215 RSET = 3.24K 210 400 ICH (mA) ICH (mA) 500 RSET = 5.62K 300 RSET = 8.06K 200 RSET = 31.6K 190 0 2.7 2.9 3.1 3.3 200 195 RSET = 16.2K 100 205 3.5 3.7 3.9 4.1 4.3 185 -40 VBAT (V) 6 -15 10 35 60 85 Temperature (°C) www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Typical Characteristics–Battery Charger End of Charge Voltage Regulation vs. Temperature End of Charge Battery Voltage vs. Input Voltage (VIN = 5V; RSET = 8.06kΩ Ω) 4.206 4.215 4.204 RSET = 8.06kΩ VBAT_EOC (V) VBAT_EOC (V) 4.210 4.205 4.200 4.195 4.202 4.200 RSET = 31.6kΩ 4.198 4.196 4.190 4.185 -40 -15 10 35 60 4.194 4.5 85 5 5.5 Recharging Threshold Voltage vs. Temperature (RSET = 8.06kΩ Ω) Constant Charging Current vs. Input Voltage (VIN = 5.62V) 4.16 310 4.14 VIN = 3.3V 305 ICH (mA) 4.12 4.10 4.08 VIN = 4V 300 VIN = 3.6V 295 290 4.06 4.04 -40 6.5 VIN (V) Temperature (°C) VRCH (V) 6 -15 10 35 60 285 85 4 4.5 5 5.5 6 6.5 VIN (V) Temperature (°C) Preconditioning Charge Current vs. Temperature (RSET = 8.06kΩ Ω) Preconditioning Voltage Threshold vs. Temperature (RSET = 8.06kΩ Ω) 3.03 20.8 3.02 3.01 VMIN (V) ITK (mA) 20.4 20.0 3.00 2.99 19.6 2.98 19.2 -40 2.97 -15 10 35 60 85 Temperature (°C) 2552.2008.02.1.2 -40 -15 10 35 60 85 Temperature (°C) www.analogictech.com 7 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Typical Characteristics–Battery Charger Enable Threshold High vs. Input Voltage Enable Threshold Low vs. Input Voltage (RSET = 8.06kΩ Ω) (RSET = 8.06kΩ Ω) 1.1 1.2 -40°C -40°C 1.0 VEN(L) (V) VEN(H) (V) 1.1 1.0 0.9 0.9 0.8 85°C 0.8 0.7 4.0 4.5 5.0 5.5 6.0 6.5 0.6 4.0 VIN (V) 8 85°C 0.7 25°C 25°C 4.5 5.0 5.5 6.0 6.5 VIN (V) www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Typical Characteristics–Step-Down Converter Efficiency vs. Load DC Regulation (VOUT = 3.3V; L = 5.6µH) (VOUT = 3.3V; L = 5.6µH) 100 1.0 VIN = 3.6V Output Error (%) Efficiency (%) 90 VIN = 5.0V 80 VIN = 4.2V 70 60 50 40 0.1 1 10 100 0.5 VIN = 5.0V 0.0 VIN = 3.6V -1.0 0.1 1000 VIN = 4.2V -0.5 1 Output Current (mA) 10 100 1000 Output Current (mA) Efficiency vs. Load DC Regulation (VOUT = 1.8V; L = 3.3µH) (VOUT = 1.2V; L = 1.5μH) 100 1.0 VIN = 3.6V VIN = 2.7V Output Error (%) Efficiency (%) 90 80 VIN = 5.0V 70 VIN = 4.2V 60 0.5 VIN = 3.6V VIN = 5.0V 0.0 VIN = 4.2V -0.5 VIN = 2.7V 50 -1.0 0.1 40 0.1 1 10 100 1000 1 Efficiency vs. Load DC Regulation (VOUT = 1.2V; L = 1.5µH) (VOUT = 1.2V; L = 1.5μH) 100 1000 1.0 90 VIN = 3.6V Output Error (%) Efficiency (%) 100 Output Current (mA) Output Current (mA) 80 10 VIN = 2.7V VIN = 5.0V 70 60 VIN = 4.2V 50 40 0.1 1 10 100 1000 0.5 VIN = 5.0V 0.0 VIN = 4.2V -0.5 -1.0 0.1 1 10 VIN = 2.7V 100 1000 Output Current (mA) Output Current (mA) 2552.2008.02.1.2 VIN = 3.6V www.analogictech.com 9 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Typical Characteristics–Step-Down Converter Line Regulation Soft Start (VOUT = 1.8V) (VIN = 3.6V; VOUT = 1.8V; IOUT = 150mA) Accuracy (%) 0 Enable and Output Voltage (top) (V) IOUT = 10mA 0.1 IOUT = 50mA -0.1 -0.2 -0.3 IOUT = 150mA -0.4 2.7 3.1 3.5 3.9 4.3 4.7 5.1 4 VEN 3 VOUT 2 1 0 IL 0.3 0.2 0.1 0.0 5.5 Input Voltage (V) Inductor Current (bottom) (A) 0.2 Time (100µs/div) Output Voltage Accuracy vs. Temperature No Load Quiescent Current vs. Input Voltage (VIN = 3.6V; VO = 1.8V; IOUT = 150mA) 70 1.5 1.0 85°C 60 0.5 IQ (mA) Output Accuracy (%) 2.0 0.0 -0.5 -1.0 25°C 50 40 -40°C -1.5 -2.0 -40 -15 10 35 60 30 2.7 85 3.1 3.5 3.9 4.3 4.7 5.1 Temperature (°°C) Input Voltage (V) N-Channel RDS(ON) vs. Input Voltage P-Channel RDS(ON) vs. Input Voltage 5.5 600 1000 85°C 900 85°C RDS(ON)H (mΩ Ω) RDS(ON)L (mΩ Ω) 500 100°C 800 120°C 700 600 500 400 300 2.5 3 3.5 4 4.5 5 5.5 6 300 100 2.5 VIN (V) 10 120°C 400 25°C 200 25°C 100°C 3 3.5 4 4.5 5 5.5 6 VIN (V) www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Typical Characteristics–Step-Down Converter Load Transient Response Line Transient Response (10mA to 300mA; VIN = 3.6V; VOUT = 1.8V; COUT = 4.7µF; C = 100pF) (VOUT = 1.8V @ 150mA, CFF = 100pF) 1.8 1.7 1.6 IOUT 300mA 10mA ILX 0.2 0.0 -0.2 Output Voltage (top) (V) Output Voltage (top) (V) VOUT 1.90 1.85 1.80 1.75 4.6 4.1 3.6 3.1 Time (25µs/div) Output Voltage Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 1mA) 1.80 1.79 0.4 0.3 0.2 0.1 Time (0.2µs/div) 40 20 0 -20 0.05 0.00 -0.05 -0.10 Inductor Current (bottom) (A) 1.81 Output Voltage (AC coupled) (top) (V) Output Voltage Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 300mA) Inductor Current (bottom) (A) Output Voltage (AC coupled) (top) (V) Time (20µs/div) 2552.2008.02.1.2 Input Voltage (bottom) (V) 1.9 Load and Inductor Current (bottom) (A) 2.0 Time (5µs/div) www.analogictech.com 11 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Typical Characteristics–LDO Regulator Quiescent Current vs. Temperature Dropout Voltage vs. Temperature (VIN = 5V) 0.5 120 Dropout Voltage (V) 110 IQ (µA) 100 90 80 70 60 -15 10 35 60 IL = 200mA 0.3 0.2 IL = 100mA 0.1 0.0 -40 50 -40 IL = 300mA 0.4 85 IL = 50mA -20 0 20 Temperature (°°C) 40 60 80 100 120 Temperature (°°C) Dropout Voltage vs. Output Current LDO Dropout Characteristics (EN = GND; ENLDO = VIN) 0.5 3.00 85°C Dropout Voltage (V) Output Voltage (V) 3.20 IOUT = 0mA 2.80 IOUT = 300mA IOUT = 150mA 2.60 2.40 2.20 IOUT = 10mA IOUT = 100mA IOUT = 50mA 25°C 0.4 0.3 0.2 -40°C 0.1 0.0 2.00 2.70 0 2.80 2.90 3.00 3.10 3.20 50 100 150 200 250 300 3.30 Output Current (mA) Input Voltage (V) Output Voltage vs. Temperature Enable Threshold Voltage vs. Input Voltage (VIN = 3.6V; VO = 1.8V; IOUT = 150mA) 0.96 0.94 3.300 VENABLE (V) Output Voltage (V) 3.301 3.299 3.298 0.92 VEN(H) 0.9 0.88 0.86 3.297 VEN(L) 0.84 3.296 -40 -15 10 35 60 85 0.82 2.7 Temperature (°°C) 12 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Typical Characteristics–LDO Regulator Line Transient Response Load Transient Response (IOUT = 300mA) (1mA to 300mA; VIN = 5.0V; VOUT = 3.3V) 3.30 5.0 VIN 4.5 4.0 Output Voltage (top) (V) Output Voltage (top) (V) VOUT 3.6 3.4 3.2 VOUT 0.4 IL 0.2 0.0 -0.2 Time (100µs/div) Time (100µs/div) Turn-On Time From Enable (VIN = 4.2V; IOUT = 300mA) (VIN = 4.2V; IOUT = 300mA) VEN = 2V/div VOUT = 1V/div Enable and Output Voltage Turn-Off Response Time Enable and Output Voltage Output Current (bottom) (A) 3.35 Input Voltage (bottom) (V) 3.40 Time (50µs/div) VEN = 2V/div VOUT = 1V/div Time (100µs/div) LDO Output Noise (COUT = 4.7µF; IOUT = 10mA; RLOAD = 330; 98.33µVrms) nVrms/sqrt (Hz) 10000 1000 100 10 0.01 0.1 1 10 100 1000 Frequency (kHz) 2552.2008.02.1.2 www.analogictech.com 13 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Functional Block Diagram Reverse Blocking ADP BAT Current Compare CV/Pre-Charge Charge Control Constant Current ISET UVLO STAT FBB Charge Status INB EN_BAT Err. Amp DH . Voltage Reference ENB LX Logic DL Input MODE From Charger Section PGND Over-Temperature Protection INA OUTA Active Feedback Control Over-Current Protection FBA + ENA Err. Amp Fast Start Control - Voltage Reference AGND Functional Description The AAT2552 is a high performance power man-agement IC comprised of a lithium-ion/polymer battery charger, a step-down converter, and a linear regulator. The linear regulator is designed for high-speed turn-on and fast transient response, and good power supply ripple rejection. The step-down converter operates in both fixed and variable frequency modes for high efficiency performance. The switching frequency is 1.5MHz, minimizing the size of the inductor. In light load conditions, the device enters power-saving mode; the switching frequency is reduced and the converter consumes 45μA of current, making it ideal for battery-operated applications. Battery Charger 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 14 adapter/USB input voltage range from 4V to 7.5V. 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 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. Switch-Mode Step-Down Converter 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 con- www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications sumes 45μA of current, making it ideal for batteryoperated applications. The output voltage is programmable from VIN to as low as 0.6V. Power devices are sized for 300mA current capability while maintaining over 96% 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. The AAT2552 synchronous step-down converter can be synchronized to an external clock signal applied to the MODE pin. 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. Linear Regulator Current Limit / Over-Temperature Protection The advanced circuit design of the linear regulator has been specifically optimized for very fast start-up. This proprietary CMOS LDO has also been tailored for superior transient response characteristics. These traits are particularly important for applications that require fast power supply timing. 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 high-speed turn-on capability is enabled through implementation of a fast-start control circuit which accelerates the power-up behavior of fundamental control and feedback circuits within the LDO regulator. The LDO regulator output has been specifically optimized to function with low-cost, low-ESR ceramic capacitors; however, the design will allow for operation over a wide range of capacitor types. The regulator comes with complete short-circuit and thermal protection. The combination of these two internal protection circuits gives a comprehensive safety system to guard against extreme adverse operating conditions. The regulator features an enable/disable function. This pin (ENA) is active high and is compatible with CMOS logic. The LDO regulator will go into the disable shutdown mode when the voltage on the ENA pin falls below 0.6V. If the enable function is not needed in a specific application, it may be tied to INA to keep the LDO regulator in a continuously on state. Under-Voltage Lockout The AAT2552 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 2552.2008.02.1.2 The battery charger has a thermal protection circuit which will shut down charging functions when the internal die temperature exceeds the preset thermal limit threshold. Once the internal die temperature falls below the thermal limit, normal charging operation will resume. Control Loop The AAT2552 contains a compact, current mode stepdown 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 voltageprogrammed 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 www.analogictech.com 15 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications 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. Pre-conditioning continues until the battery voltage reaches VMIN (see Figure 1). 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 Preconditioning Trickle Charge Phase 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. 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. Constant Current Charge Phase Constant Voltage Charge Phase Charge Complete Voltage 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. 16 www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution 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 BAT_EOC > VBAT No Voltage Phase Test IBAT > ITERM No Charge Completed 2552.2008.02.1.2 www.analogictech.com 17 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Application Information stant current levels from 30mA to 500mA may be set by selecting the appropriate resistor value from Table 1. Soft Start / Enable Normal ICHARGE (mA) Set Resistor Value R1 (kΩ) 500 400 300 250 200 150 100 50 40 30 20 15 3.24 4.12 5.36 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. Separate ENA and ENB inputs are provided to independently enable and disable the LDO and step-down converter, respectively. This allows sequencing of the LDO and step-down outputs during startup. The step-down converter is enabled when the ENB pin is pulled high. Soft start increases the inductor current limit point in discrete steps when the input voltage or ENB input is applied. It limits the current surge seen at the input and eliminates output voltage overshoot. When pulled low, the ENB input forces the AAT2552 into a low-power, non-switching state. The step-down converter input current during shutdown is less than 1μA. 1000 ICH (mA) The LDO is enabled when the ENA pin is pulled high. The control and feedback circuits have been optimized for high-speed, monotonic turn-on characteristics. Table 1: RSET Values. 100 10 1 1 100 1000 RSET (kΩ Ω) Figure 2: Constant Charging Current vs. Set Resistor Values. 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 7.5V 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. Charge Status Output The AAT2552 provides battery charge status via a status pin. This pin is internally connected to an N-channel open drain MOSFET, which can be used to drive an external LED. The status pin can indicate several conditions, as shown in Table 2. 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 con- 18 10 Event Description Status No battery charging activity Battery charging via adapter or USB port Charging completed OFF ON OFF Table 2: LED Status Indicator. The LED should be biased with as little current as necessary to create reasonable illumination; therefore, a bal- www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 Total Power Solution for Portable Applications last 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 lowcost green or red LEDs. It is not recommended to exceed 8mA for driving an individual status LED. Figure 3 shows the relationship of maximum power dissipation and ambient temperature of the AAT2552. 3.00 2.50 PD(MAX) (mW) SystemPowerTM The required ballast resistor values can be estimated using the following formulas: 2.00 1.50 1.00 0.50 R6 = (VADP - VF(LED)) ILED 0.00 0 20 40 60 80 100 TA (°°C) Example: Figure 3: Maximum Power Dissipation. (5.5V - 2.0V) = 1.75kΩ R6 = 2mA Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA. Thermal Considerations The AAT2552 is offered in a TDFN34-16 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. Next, the power dissipation of the battery charger can be calculated by the following equation: PD = [(VADP - VBAT) · ICH + (VADP · IOP)] Where: PD VADP VBAT ICH IOP = = = = Total Power Dissipation by the Device ADP/USB Voltage Battery Voltage as Seen at the BAT Pin Constant Charge Current Programmed for the Application = 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. First, the maximum power dissipation for a given situation should be calculated: ICH(MAX) = (TJ(MAX) - TA) - V · I IN OP θJA ICH(MAX) = VIN - VBAT (TJ(MAX) - TA) PD(MAX) = θJA 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) 2552.2008.02.1.2 (PD(MAX) - VIN · IOP) VIN - VBAT 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. www.analogictech.com 19 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Capacitor Selection 500 450 ICH(MAX) (mA) Linear Regulator Input Capacitor (C6) TA = 25°C 400 350 300 TA = 60°C 250 TA = 45°C 200 150 TA = 85°C 100 50 0 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 6.75 7 VIN (V) Figure 4: Maximum Charging Current Before Thermal Cycling Becomes Active. There are three types of losses associated with the stepdown 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 An input capacitor greater than 1μF will offer superior input line transient response and maximize power supply ripple rejection. Ceramic, tantalum, or aluminum electrolytic capacitors may be selected for CIN. There is no specific capacitor ESR requirement for CIN. However, for 300mA LDO regulator output operation, ceramic capacitors are recommended for CIN due to their inherent capability over tantalum capacitors to withstand input current surges from low impedance sources such as batteries in portable devices. 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 (C6) + (tsw · FS · IO + IQ) · VIN IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses. For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: 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. CIN = 2 PTOTAL = IO · RDSON(H) + IQ · VIN TJ(MAX) = PTOTAL · ΘJA + TAMB 20 ⎛ VPP ⎞ - ESR · FS ⎝ IO ⎠ VO ⎛ V ⎞ 1 · 1 - O = for VIN = 2 · VO VIN ⎝ VIN ⎠ 4 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 TDFN34-16 package which is 50°C/W. VO ⎛ V ⎞ · 1- O VIN ⎝ VIN ⎠ 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. www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications The maximum input capacitor RMS current is: VO ⎛ V ⎞ · 1- O = VIN ⎝ VIN ⎠ D · (1 - D) = 0.52 = 1 2 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. IRMS = IO · VO ⎛ V ⎞ · 1- O VIN ⎝ VIN ⎠ for VIN = 2 · VO IRMS(MAX) = IO 2 The term 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 step-down converter. Low ESR/ESL X7R and X5R 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. The proper placement of the input capacitor (C6) can be seen in the evaluation board layout in Figure 7. 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 2552.2008.02.1.2 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. The linear regulator and the step-down convertor share the same input capacitor on the evaluation board. Linear Regulator Output Capacitor (C5) For proper load voltage regulation and operational stability, a capacitor is required between OUT and GND. The COUT capacitor connection to the LDO regulator ground pin should be made as directly as practically possible for maximum device performance. Since the regulator has been designed to function with very low ESR capacitors, ceramic capacitors in the 1.0μF to 10μF range are recommended for best performance. Applications utilizing the exceptionally low output noise and optimum power supply ripple rejection should use 2.2μF or greater for COUT. In low output current applications, where output load is less than 10mA, the minimum value for COUT can be as low as 0.47μF. Battery Charger Output Capacitor (C2) The battery charger of the AAT2552 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 AAT2552 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 (C3) 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 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 volt- www.analogictech.com 21 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications age 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 hot-spot 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 current down slope meets the internal slope compensation requirements. The internal slope compensation for the AAT2552 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= 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. Adjustable Output Voltage for the Step-down Converter Resistors R2 and R3 of Figure 5 program the output of the step down converter and 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 R3 is 59kΩ. Decreased resistor values are necessary to maintain noise immunity on the FBB pin, resulting in increased quiescent current. Table 3 summarizes the resistor values for various output voltages. ⎛ VOUT ⎞ ⎛ 3.3V ⎞ R2 = V -1 · R3 = 0.6V - 1 · 59kΩ = 267kΩ ⎝ REF ⎠ ⎝ ⎠ With enhanced transient response for extreme pulsed load application, an external feed-forward capacitor (C8 in Figure 5) can be added. VOUT (V) R3 = 59kΩ R2 (kΩ) R3 = 221kΩ R2 (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 0.75 ⋅ VO 0.75 ⋅ 1.8V A = = 0.45 L 3.0µH µsec 0.75 ⋅ VO = m µsec 0.75 ⋅ VO ≈ 1.67 A ⋅ VO A 0.45A µsec For most designs, the step-down converter operates with inductor values from 1μH to 4.7μH. Table 6 displays inductor values for the AAT2552 for various output voltages. Manufacturer’s specifications list both the inductor DC current rating, which is a thermal limitation, and the 22 Table 3: Adjustable Resistor Values For Step-Down Converter. www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Adjustable Output Voltage for the LDO The output voltage for the LDO can be programmed by an external resistor divider network. As shown below, the selection of R4 and R5 is a straightforward matter. R5 is chosen by considering the tradeoff between the feedback network bias current and resistor value. Higher resistor values allow stray capacitance to become a larger factor in circuit performance whereas lower resistor values increase bias current and decrease efficiency. To select appropriate resistor values, first choose R5 such that the feedback network bias current is reasonable. Then, according to the desired VOUT, calculate R4 according to the equation below. An example calculation follows. R4 = ⎛ VOUT ⎞ - 1 · R5 ⎝ VREF ⎠ Printed Circuit Board Layout Considerations For the best results, it is recommended to physically place the battery pack as close as possible to the AAT2552 BAT pin. To minimize voltage drops on the PCB, keep the high current carrying traces adequately wide. Refer to the AAT2552 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. 2. 3. An R5 value of 59kΩ is chosen, resulting in a small feedback network bias current of 1.24V/59kΩ ≈ 21μA. The desired output voltage is 1.8V. From this information, R4 is calculated from the equation below. The result is R4 = 26.64kΩ. Since 26.64kΩ is not a standard 1%-value, 26.7kΩ is selected. From this example calculation, for VOUT = 1.8V, use R5 = 59kΩ and R4 = 26.7kΩ. Example output voltages and corresponding resistor values are provided in Table 4. R4 Standard 1% Values (R5 = 59kΩ) VOUT (V) R4 (kΩ) 3.3 2.8 2.5 2.0 1.8 1.5 97.6 75.0 60.4 36.5 26.7 12.4 4. 5. The input capacitors (C1, C6) should connect as closely as possible to ADP, INA, and INB. It is possible to use two input capacitors for INA and INB. 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. The feedback pin should be separate from any power trace and connect as closely as possible to the load point. Sensing along a high-current load trace will degrade DC load regulation. Feedback resistors should be placed as closely as possible to the FBB pin 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. The resistance of the trace from PGND 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. A high density, small footprint layout can be achieved using an inexpensive, miniature, non-shielded, high DCR inductor. Table 4: Adjustable Resistor Values for the LDO. 2552.2008.02.1.2 www.analogictech.com 23 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications JP1 2 1 EN_BAT 3 2 1 Power Selection BAT ADP D1 RED LED C1 10μF R6 1.5K Sync/Mode 1 6 L1 12 C4 100pF R2 (Optional) C3 4.7μF 1 2 EN_LDO JP3 U1 15 16 VoB JP2 C6 10μF (at bottom layer) ADP STAT EN_BAT MODE LX INA INB ENA ENB 10 1 11 2 7 5 BAT 14 4 FBB ISET 2 3 AGND OUTA 9 13 PGND FBA 8 EN_BUCK VoA C2 10μF R1 8.06K R4 R3 59k C5 4.7μF R5 59k L1 VOUTB (V) R2 (Ω) 0.6 13 1.2 1.8 2.5 3.0 3.3 R2 short, R3 open 9.2K 59K 118K 187K 237K 267K VOUTA (V) 1.24 1.5 1.8 2.0 2.5 2.8 3.0 1.5μH (CDRH2D09/HP; DCR 88mΩ; 730mA @ 20°C) 2.2μH (CDRH2D09/HP; DCR 115mΩ; 600mA @ 20°C) 3.0μH (CDRH2D09/HP; DCR 150mΩ; 470mA @ 20°C) 3.9μH (CDRH2D09/HP; DCR 180mΩ; 450mA @ 20°C) 4.7μH (CDRH2D09/HP; DCR 230mΩ; 410mA @ 20°C) 5.6μH (CDRH2D09/HP; DCR 260mΩ; 370mA @ 20°C) R4 (Ω) R4 short, R5 open 12.4K 26.7K 36.5K 60.4K 75.0K 97.6K Figure 5: AAT2552 Evaluation Board Schematic. Figure 6: AAT2552 Evaluation Board Top Side Layout. 24 Figure 7: AAT2552 Evaluation Board Bottom Side Layout. www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Component Part Number Description Manufacturer U1 C1, C2 C3, C5 C6 C4 L1 R6 R1 R2 R3, R5 R4 JP1, JP2, JP3, JP4 D1 AAT2552IRN ECJ-1VB0J106M GRM188R60J475KE19 GRM319R61A106KE19 GRM1886R1H101JZ01J CDRH2D09 Chip Resistor Chip Resistor Chip Resistor Chip Resistor Chip Resistor PRPN401PAEN CMD15-21SRC/TR8 Total Power Solution for Portable Applications CER 10μF 6.3V X5R 0603 CER 4.7μF 6.3V X5R 0603 CER 10μF 10V X5R 1206 CER 100pF 50V 5% R2H 0603 Shielded SMD, 3x3x1mm 1.5KΩ, 5%, 1/4W 0603 8.06KΩ, 1%, 1/4W 0603 118KΩ, 1%, 1/4W 0603 59KΩ, 1%, 1/4W 0603 60.4KΩ, 1%, 1/4W 0603 Conn. Header, 2mm zip Red LED 1206 AnalogicTech Panansonic Murata Murata Murata Sumida Vishay Vishay Vishay Vishay Vishay Sullins Electronics Chicago Miniature Lamp Table 5: AAT2552 Evaluation Board Component Listing. 2552.2008.02.1.2 www.analogictech.com 25 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Step-Down Converter Design Example (to be updated) Specifications VO VIN FS TAMB = = = = 1.8V @ 250mA, Pulsed Load ΔILOAD = 200mA 2.7V to 4.2V (3.6V nominal) 1.5MHz 85°C 1.8V Output Inductor L1 = 1.67 µsec µsec ⋅ VO2 = 1.67 ⋅ 1.8V = 3µH (use 3.0μH; see Table 3) A A For Sumida inductor CDRH2D09-3R0, 3.0μH, DCR = 150mΩ. ⎛ VO V ⎞ 1.8V 1.8V ⎞ ⎛ ⋅ 1- O = ⋅ 1= 228mA L1 ⋅ FS ⎝ VIN⎠ 3.0µH ⋅ 1.5MHz ⎝ 4.2V ⎠ ΔIL1 = 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 = L1 · FS · VIN(MAX) 2 · 3 3.0µH · 1.5MHz · 4.2V 2· 3 1 · Pesr = esr · IRMS2 = 5mΩ · (66mA)2 = 21.8µW 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 26 www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications AAT2552 Losses PTOTAL = IO2 · (RDSON(H) · VO + RDSON(L) · [VIN -VO]) VIN + (tsw · FS · IO + IQ) · VIN = 0.22 · (0.59Ω · 1.8V + 0.42Ω · [4.2V - 1.8V]) 4.2V + (5ns · 1.5MHz · 0.2A + 30µA) · 4.2V = 26.14mW TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (50°C/W) · 26.14mW = 86.3°C 2552.2008.02.1.2 www.analogictech.com 27 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Output Voltage VOUTB (V) R3 = 59kΩ R3 (kΩ) R3 = 221kΩ R1 (kΩ) L1 (μH) 0.6 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 3.3 R2 short, R3 open 19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7 118 124 137 187 237 267 R2 short, R3 open 75 113 150 187 221 261 301 332 442 464 523 715 887 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 4.9 5.6 Table 6: Step-Down Converter Component Values. Manufacturer Part Number Inductance (μH) Max DC Current (mA) DCR (mΩ) Size (mm) LxWxH Type Sumida Sumida Sumida Sumida Sumida Sumida Sumida Sumida Sumida Sumida Sumida Taiyo Yuden Taiyo Yuden Taiyo Yuden Taiyo Yuden FDK FDK FDK FDK CDRH2D09-1R5 CDRH2D09-2R2 CDRH2D09-2R5 CDRH2D09-3R0 CDRH2D09-3R9 CDRH2D09-4R7 CDRH2D09-5R6 CDRH2D11-1R5 CDRH2D11-2R2 CDRH2D11-3R3 CDRH2D11-4R7 NR3010T1R5N NR3010T2R2M NR3010T3R3M NR3010T4R7M MIPWT3226D-1R5 MIPWT3226D-2R2 MIPWT3226D-3R0 MIPWT3226D-4R2 1.5 2.2 2.5 3.0 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 3.0 4.2 730 600 530 470 450 410 370 900 780 600 500 1200 1100 870 750 1200 1100 1000 900 110 144 150 194 225 287 325 68 98 123 170 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, R3 = 221kΩ. 28 www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Manufacturer Part Number Value (μF) Voltage Rating Temp. Co. Case Size Murata Murata Murata Murata Murata Murata GRM21BR61A106KE19 GRM188R60J475KE19 GRM188R61A225KE34 GRM188R60J225KE19 GRM188R61A105KA61 GRM185R60J105KE26 10 4.7 2.2 2.2 1.0 1.0 10 6.3 10 6.3 10 6.3 X5R X5R X5R X5R X5R X5R 0805 0603 0603 0603 0603 0603 Table 8: Surface Mount Capacitors. 2552.2008.02.1.2 www.analogictech.com 29 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN34-16 UVXYY AAT2552IRN-CAE-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/about/quality.aspx. Legend Voltage Adjustable (0.6) 0.9 Adjustable (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. 30 www.analogictech.com 2552.2008.02.1.2 PRODUCT DATASHEET AAT2552178 SystemPowerTM Total Power Solution for Portable Applications Package Information1 TDFN34-16 3.000 ± 0.050 1.600 ± 0.050 Detail "A" 3.300 ± 0.050 4.000 ± 0.050 Index Area 0.350 ± 0.100 Top View 0.230 ± 0.050 Bottom View C0.3 (4x) 0.050 ± 0.050 0.450 ± 0.050 0.850 MAX Pin 1 Indicator (optional) 0.229 ± 0.051 Side View Detail "A" All dimensions in millimeters. 1. 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. Advanced Analogic Technologies, Inc. 3230 Scott Boulevard, Santa Clara, CA 95054 Phone (408) 737-4600 Fax (408) 737-4611 © 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. 2552.2008.02.1.2 www.analogictech.com 31