AAT2554 Total Power Solution for Portable Applications General Description Features The AAT2554 is a fully integrated 500mA battery charger, a 250mA step-down converter, and a 300mA low dropout (LDO) linear regulator. The input voltage range is 4V to 6.5V 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. • • 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 15mA 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. It has independent input and enable pins. The output voltage ranges from 0.6V to the input voltage. • • • The AAT2554 linear regulator is designed for fast transient response and good power supply ripple rejection. Designed for 300mA of load current, it includes short-circuit protection and thermal shutdown. 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 Linear Regulator: — 300mA Output Current — Low Dropout: 400mV at 300mA — Fast Line and Load Transient Response — High Accuracy: ±1.5% — 70µA Quiescent Current Short-Circuit, Over-Temperature, and Current Limit Protection TDFN34-16 Package -40°C to +85°C Temperature Range Applications The AAT2554 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 Handheld Instruments MP3 and Portable Music Players PDAs and Handheld Computers Portable Media Players Typical Application Adapter/USB Input Enable ADP VINB STAT ENB VINA EN_BAT L= 3.0µH LX ENA AAT2554 RFB2 BATT+ BAT RFB1 C OUTB System VOUTB FB VOUTA OUTA C OUTA C OUT ISET GND R SET BATT- Battery Pack 2554.2007.01.1.2 1 AAT2554 Total Power Solution for Portable Applications Pin Descriptions Pin # Symbol 1 FB 2, 10, 12, 14 3 GND ENB 4 VINA 5 6 OUTA EN_BAT 7 ISET 8 9 11 13 BAT STAT ADP ENA 15 LX 16 EP VINB 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 consumes less than 1µA of current. When connected to logic high, the converter resumes normal operation. Linear regulator input voltage. Connect a 1µF or greater capacitor from this pin to ground. Linear regulator output. Connect a 2.2µF capacitor from this pin to ground. 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 resumes normal operation. Charge current set point. Connect a resistor from this pin to ground. Refer to typical characteristics curves for resistor selection. Battery charging and sensing. Charge status input. Open drain status output. Input for USB/adapter charger. 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, it resumes normal operation. 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 TDFN34-16 (Top View) FB GND ENB VINA OUTA EN_BAT ISET BAT 2 1 16 2 15 3 14 4 13 5 12 6 11 7 10 8 9 VINB LX GND ENA GND ADP GND STAT 2554.2007.01.1.2 AAT2554 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. 2554.2007.01.1.2 3 AAT2554 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 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 VINB Rising Hysteresis VINB Falling IOUTB = 0 to 250mA, VINB = 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 ENB = GND VINB 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 VINB = 5.5V, VLX = 0 to VINB VINB = 2.7V to 5.5V VINB = 3.6V VOUTB = 1.0V 1.0 0.591 From Enable to Output Regulation 0.2 0.6 0.609 0.2 0.6 VINB = VENB = 5.5V 1.4 -1.0 1.0 1. The AAT2554 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 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Electrical Characteristics1 VINA = VOUT(NOM) + 1V for VOUT options greater than 1.5V. IOUT = 1mA, COUT = 2.2µF, CIN = 1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol Description Conditions Min Typ Max Units 1.5 2.5 % 5.5 V 600 mV Linear Regulator VOUT VIN Output Voltage Tolerance IOUTA = 1mA to 300mA TA = 25°C TA = -40°C to +85°C Input Voltage -1.5 -2.5 VOUT + VDO2 VDO ΔVOUT/ VOUT*ΔVIN Dropout Voltage3 IOUTA = 300mA 400 Line Regulation VINA = VOUTA + 1 to 5.0V 0.09 %/V ΔVOUT(Line) Dynamic Line Regulation 2.5 mV ΔVOUT(Load) IOUT ISC IQ ISHDN Dynamic Load Regulation Output Current Short-Circuit Current Quiescent Current Shutdown Current 60 mV mA mA µA µA PSRR TSD THYS eN TC TEN_DLY VEN(L) VEN(H) IEN Power Supply Rejection Ratio Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis Output Noise Output Voltage Temperature Coefficient Enable Time Delay Enable Threshold Low Enable Threshold High Enable Input Current IOUTA = 300mA, VINA = VOUTA + 1 to VOUTA + 2, TR/TF = 2µs IOUTA = 1mA to 300mA, TR <5µs VOUTA > 1.2V VOUTA < 0.4V VINA = 5V; ENA = VIN VINA = 5V; ENA = 0V 1kHz IOUTA =10mA 10kHz 1MHz 300 600 70 125 1.0 65 45 43 dB 145 °C 12 °C 250 µVRMS 22 ppm/°C 15 µs V V µA 0.6 1.5 VENA = 5.5V 1.0 1. The AAT2554 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. VDO is defined as VIN - VOUT when VOUT is 98% of nominal. 3. For VOUT <2.3V, VDO = 2.5V - VOUT. 2554.2007.01.1.2 5 AAT2554 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 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) Enable Threshold High VEN(L) Enable Threshold Low 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_BAT = 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 AAT2554 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. 6 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Typical Characteristics – Step-Down Converter Efficiency vs. Load DC Load Regulation (VOUT = 1.8V; L = 3.3µH) (VOUT = 1.8V; L = 3.3µH) 100 1.0 Efficiency (%) VIN = 5.0V Output Error (%) VIN = 2.7V 90 VIN = 3.6V 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) 1000 (VOUT = 1.2V; L = 1.5µH) 1.0 100 Output Error (%) VIN = 2.7V 90 Efficiency (%) 100 DC Load Regulation (VOUT = 1.2V; L = 1.5µH) VIN = 3.6V 70 60 VIN = 5.5V VIN = 5.0V 50 VIN = 5.5V 0.0 VIN = 3.6V 1 10 100 1000 10 100 Soft Start Line Regulation (VIN = 3.6V; VOUT = 1.8V; IOUT = 250mA; CFF = 100pF) (VOUT = 1.8V) VEN 0.5 0.8 0.0 0.6 VO 0.4 0.2 -2.0 0.0 -3.0 IL -0.2 -5.0 -0.4 Inductor Current (bottom) (A) 1.0 1.0 Accuracy (%) 1.4 1.2 1000 0.6 1.6 2.0 -4.0 1 Output Current (mA) 3.0 -1.0 -1.0 0.1 Output Current (mA) 5.0 4.0 VIN = 4.2V -0.5 VIN = 2.7V 30 0.1 VIN = 5.0V 0.5 VIN = 4.2V 40 Enable and Output Voltage (top) (V) 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) 2554.2007.01.1.2 7 AAT2554 Total Power Solution for Portable Applications Typical Characteristics – Step-Down Converter Output Voltage Error vs. Temperature Switching Frequency Variation vs. Temperature (VINB = 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 -10.0 -20 0 20 40 60 80 100 -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 Supply Current (µA) Frequency Variation (%) 2.0 1.0 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 3.5 3.9 4.3 4.7 5.1 Input Voltage (V) Input Voltage (V) P-Channel RDS(ON) vs. Input Voltage N-Channel RDS(ON) vs. Input Voltage 5.5 750 900 120°C 700 100°C 120°C 650 85°C 800 RDS(ON)L (mΩ Ω) RDS(ON)H (mΩ Ω) 40 10 2.7 5.5 1000 700 600 25°C 500 45 100°C 600 85°C 550 500 450 400 400 2.5 3.0 3.5 4.0 4.5 Input Voltage (V) 8 25°C 350 300 5.0 5.5 6.0 300 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Input Voltage (V) 2554.2007.01.1.2 AAT2554 Total Power Solution 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 0.07 0.06 VO 0 0.05 -20 0.04 -40 0.03 -60 0.02 -80 0.01 IL -100 0.00 -120 -0.01 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 Time (2µs/div) Output Ripple (VIN = 3.6V; VOUT = 1.8V; IOUT = 250mA) 20 0.8 0.7 VO 0 0.6 -20 0.5 -40 0.4 -60 0.3 -80 0.2 IL -100 0.1 -120 0.0 Inductor Current (bottom) (A) Output Voltage (AC Coupled) (top) (V) 40 Time (200ns/div) 2554.2007.01.1.2 9 AAT2554 Total Power Solution 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 = 5.36kΩ 300 RSET = 8.06kΩ 200 100 RSET = 16.2kΩ RSET = 31.6kΩ 3.1 3.7 0 1 1 10 100 2.7 1000 2.9 3.3 3.5 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 4.21 4.20 4.19 4.18 4.194 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 25 50 75 100 Constant Charging Current vs. Temperature (RSET = 8.06kΩ Ω) (RSET = 8.06kΩ Ω) 210 220 208 205 210 VBAT = 3.3V ICH (mA) ICH (mA) 0 Temperature (°C) VADP (V) 200 190 VBAT = 3.6V VBAT = 4V 203 200 198 195 180 193 190 170 4 4.25 4.5 4.75 5 5.25 5.5 VADP (V) 10 5.75 6 6.25 6.5 -50 -25 0 25 50 75 100 Temperature (°C) 2554.2007.01.1.2 AAT2554 Total Power Solution 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 VMIN (V) IOP (µA) 500 450 400 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 40 RSET = 5.36kΩ 30 RSET = 8.06kΩ 20 0 19.2 50 75 100 RSET = 31.6kΩ RSET = 16.2kΩ 10 19.4 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4 Temperature (°C) VADP (V) Recharging Threshold Voltage vs. Temperature Sleep Mode Current vs. Supply Voltage (RSET = 8.06kΩ Ω) (RSET = 8.06kΩ Ω) 800 4.18 700 4.16 85°C 600 ISLEEP (nA) 4.14 VRCH (V) RSET = 3.24kΩ 50 25 100 60 20.6 0 75 Preconditioning Charge Current vs. Supply Voltage 20.8 -25 50 Temperature (°C) Preconditioning Charge Current vs. Temperature -50 25 4.12 4.10 4.08 500 400 300 4.06 200 4.04 100 25°C -40°C 0 4.02 -50 -25 0 25 50 Temperature (°C) 2554.2007.01.1.2 75 100 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 VADP (V) 11 AAT2554 Total Power Solution 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 1.1 VEN(L) (V) VEN(H) (V) -40°C 1 0.9 25°C 0.8 85°C 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) 12 0.9 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) 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Typical Characteristics – LDO Regulator Dropout Voltage vs. Temperature Dropout Characteristics 3.2 IL = 300mA 480 420 360 300 IL = 100mA IL = 150mA 240 180 120 60 IL = 50mA 0 -40 -30 -20 -10 0 IOUT = 0mA 3.0 Output Voltage (V) Dropout Voltage (mV) 540 2.8 IOUT = 300mA IOUT = 150mA 2.6 2.4 2.2 IOUT = 10mA 2.0 2.7 10 20 30 40 50 60 70 80 90 100 110 120 2.8 Temperature (°C) 2.9 3.1 3.2 3.3 Ground Current vs. Input Voltage 90 500 80 Ground Current (µA) 450 400 350 300 85°C 250 200 25°C 150 -40°C 100 50 0 70 60 IOUT = 300mA 50 IOUT = 150mA IOUT = 50mA 40 IOUT = 0mA 30 IOUT = 10mA 20 10 0 0 50 100 150 200 250 300 2 2.5 3 3.5 4 4.5 5 Input Voltage (V) Output Current (mA) Output Voltage vs. Temperature Quiescent Current vs. Temperature 1.203 100 90 1.202 80 Output Voltage (V) Quiescent Current (μA) 3.0 Input Voltage (V) Dropout Voltage vs. Output Current Dropout Voltage (mV) IOUT = 100mA IOUT = 50mA 70 60 50 40 30 20 10 0 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 Temperature (°C) 2554.2007.01.1.2 1.201 1.200 1.199 1.198 1.197 1.196 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 Temperature (°C) 13 AAT2554 Total Power Solution for Portable Applications Typical Characteristics – LDO Regulator LDO Turn-On Time from Enable LDO Initial Power-Up Response Time 5 5 4 4 3 3 2 2 1 1 0 0 Enable Voltage (top) (V) 6 6 4 5 3 4 2 3 1 2 0 Output Voltage (bottom) (V) 6 Output Voltage (bottom) (V) Input Voltage (top) (V) (VIN Present) 7 1 0 Time (5µs/div) Time (50µs/div) Turn-Off Response Time Line Transient Response (I = 100mA) 6 Input Voltage (V) 5 VOUT (1V/div) 3.03 VIN 4 3.02 3 3.01 2 3.00 VOUT 1 2.99 0 2.98 Time (50µs/div) Time (100µs/div) Load Transient Response 300mA 2.85 400 2.80 300 2.75 200 2.70 100 2.65 0 IOUT 2.60 -100 Output Voltage (V) 500 3.0 800 2.9 700 2.8 2.7 600 VOUT 500 2.6 400 2.5 300 2.4 2.3 200 100 IOUT 2.2 0 2.1 Time (100µs/div) 14 Output Current (mA) 2.90 Output Current (mA) Output Voltage (V) Load Transient Response VOUT Output Voltage (V) VEN (5V/div) 3.04 -100 Time (10µs/div) 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Typical Characteristics – LDO Regulator Over-Current Protection VEN(L) and VEN(H) vs. VIN Enable Threshold Voltage (V) (EN = GND; ENLDO = VIN) Output Current (mA) 1200 1000 800 600 400 200 0 -200 Time (50ms/div) 2554.2007.01.1.2 1.250 1.225 1.200 VEN(H) 1.175 1.150 1.125 VEN(L) 1.100 1.075 1.050 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) 15 AAT2554 Total Power Solution for Portable Applications Functional Block Diagram Reverse Blocking BAT ADP Charge Control - STAT Constant Current + + ISET - VREF OverTemperature Protection EN_BAT UVLO VINB DH VINA Err. Amp. LX Logic VREF DL OverCurrent Protection ENB FB + VREF OUTA ENA GND Functional Description Battery Charger The AAT2554 is a high performance power management 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 stepdown 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 30µA of current, making it ideal for batteryoperated applications. 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 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. 16 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Switch-Mode Step-Down Converter Under-Voltage Lockout 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. 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. The AAT2554 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. Linear Regulator The advanced circuit design of the linear regulator has been specifically optimized for very fast startup. 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. 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 lowcost, 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. To assure the LDO regulator will switch on, the ENA turn-on control level must be greater than 1.5V. 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 VINA to keep the LDO regulator in a continuously on state. 2554.2007.01.1.2 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 thermal limit threshold. Once the internal die temperature falls below the thermal limit, normal charging operation will resume. Control Loop The AAT2554 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 17 AAT2554 Total Power Solution for Portable Applications 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. 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. 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. 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. Pre-conditioning continues until the battery voltage reaches VMIN (see Figure 1). At this point, the 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. 18 2554.2007.01.1.2 AAT2554 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 ADP > VBAT No Voltage Phase Test IBAT > ITERM No Charge Completed 2554.2007.01.1.2 19 AAT2554 Total Power Solution for Portable Applications Application Information Soft Start / Enable 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 reenabled, 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. le 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. Normal ICHARGE (mA) Set Resistor Ω) 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 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 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. 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 trick20 Table 1: RSET Values. 1000 ICH (mA) 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 AAT2554 into a low-power, non-switching state. The total input current during shutdown is less than 1µA. 100 10 1 1 10 100 1000 RSET (kΩ Ω) Figure 2: Constant Charging Current vs. Set Resistor Values. Charge Status Output The AAT2554 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. 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Event Description Status No battery charging activity Battery charging via adapter or USB port Charging completed OFF First, the maximum power dissipation for a given situation should be calculated: ON PD(MAX) = OFF Table 2: LED Status Indicator. 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. (TJ(MAX) - TA) 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) Figure 3 shows the relationship of maximum power dissipation and ambient temperature of the AAT2554. The required ballast resistor values can be estimated using the following formulas: 3000 PD(MAX) (mW) 2500 (VADP - VF(LED)) R 1= ILED 2000 1500 1000 500 Example: 0 0 R1 = 2554.2007.01.1.2 60 80 100 120 Figure 3: Maximum Power Dissipation. Next, the power dissipation of the battery charger can be calculated by the following equation: Thermal Considerations The AAT2554 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. 40 TA (°°C) (5.5V - 2.0V) = 1.75kΩ 2mA Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA. 20 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] 21 AAT2554 Total Power Solution for Portable Applications 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. ICH(MAX) = (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. ICC(MAX) (mA) 400 Given the total losses, the maximum junction temperature can be derived from the θJA for the TDFN34-16 package which is 50°C/W. TA = 60°C Capacitor Selection 300 TA = 85°C 200 100 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: IO2 · (RDSON(H) · VO + RDSON(L) · [VIN - VO]) VIN + (tsw · FS · IO + IQ) · VIN 22 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. TJ(MAX) = PTOTAL · ΘJA + TAMB 500 PTOTAL = For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: PTOTAL = IO2 · RDSON(H) + IQ · VIN (TJ(MAX) - TA) - V · I IN OP θJA ICH(MAX) = VIN - VBAT 0 4.25 IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load stepdown converter switching losses. Linear Regulator Input Capacitor (C7) 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 (C3) 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 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications capacitor in this application will minimize switching or power transient effects when the power supply is "hot plugged" in. Step-Down Converter Input Capacitor (C1) 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 = VO ⎛ V ⎞ · 1- O VIN ⎝ VIN ⎠ ⎛ VPP ⎞ - ESR · FS ⎝ IO ⎠ VO ⎛ V ⎞ 1 · 1 - O = for VIN = 2 · VO VIN ⎝ VIN ⎠ 4 CIN(MIN) = 1 ⎛ VPP ⎞ - ESR · 4 · FS ⎝ IO ⎠ The maximum input capacitor RMS current is: 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. for VIN = 2 · VO 2554.2007.01.1.2 D · (1 - D) = ⎛ 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 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. 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. VO ⎛ V ⎞ · 1- O VIN ⎝ VIN ⎠ VO ⎛ V ⎞ · 1- O = VIN ⎝ VIN ⎠ VO IO 2 The proper placement of the input capacitor (C1) can be seen in the evaluation board layout in Figure 6. 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. IRMS = IO · IRMS(MAX) = 0.52 = 1 2 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. Linear Regulator Output Capacitor (C6) For proper load voltage regulation and operational stability, a capacitor is required between OUT and GND. The COUT capacitor connection to the LDO 23 AAT2554 Total Power Solution for Portable Applications 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 (C5) The AAT2554 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 AAT2554 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 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 = 24 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 VOUT · (VIN(MAX) - VOUT) L · FS · VIN(MAX) 2· 3 · 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 current down slope meets the internal slope compensation requirements. The internal slope compensation for the AAT2554 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 L 3.0µH µsec 0.75 ⋅ VO = m 0.75 ⋅ VO µsec ≈ 1.67 A ⋅ VO A 0.45A µsec 3 · ΔILOAD VDROOP · FS 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications For most designs, the step-down converter operates with inductor values from 1µH to 4.7µH. Table 3 displays inductor values for the AAT2554 for various output voltages. 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. Adjustable Output Resistor Selection Resistors R2 and R3 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 R3 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. ⎛ 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. Ω R3 = 59kΩ Ω R3 = 221kΩ Output Voltage (V) L1 (µH) VOUT (V) Ω) R2 (kΩ Ω) R2 (kΩ 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 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 Table 3: Step-Down Converter Inductor Values. Table 4: Adjustable Resistor Values For Step-Down Converter. 2554.2007.01.1.2 25 AAT2554 Total Power Solution for Portable Applications VINB VINB C1 4.7µF VBAT U1 ADP ADP R4 1K C3 4.7µF 11 9 D1 VINA ADP R7 100K JP1 3 2 R5 100K ENA 3 2 ISET 1 FB GND GND GND AAT2554 8 5 15 1 2 VOUTA L1 VOUTB VOUTB 1 14 R2 118K FB 12 10 2 VOUTA R3 59K C8 100pF C4 4.7µF C8 optional for enhanced stepdown converter transient response C6 2.2µF C5 2.2µF R1 8.06K 1 ENB LX EN_BAT GND 7 ENA OUTA ENB 6 3 ENB ADP ENA 3 2 BAT VINA 13 JP2 R6 100K JP3 VINB STAT 4 VINB C7 2.2µF 16 EN_BAT 1 GND EN_BAT Figure 5: AAT2554 Evaluation Board Schematic. Printed Circuit Board Layout Considerations For the best results, it is recommended to physically place the battery pack as close as possible to the AAT2554 BAT pin. To minimize voltage drops on the PCB, keep the high current carrying traces adequately wide. Refer to the AAT2554 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, C7) should connect as closely as possible to ADP (Pin 11), VINA (Pin 4), and VINB (Pin 16). 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. 26 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 GND (Pins 2, 10, 12, and 14) 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. 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Figure 6: AAT2554 Evaluation Board Top Side Layout. Figure 7: AAT2554 Evaluation Board Bottom Side Layout. Component Part Number Description Manufacturer U1 C1, C3, C4 C5, C6, C7 C8 L1 R4 R1 R2 R3 R5, R6, R7 JP1, JP2, JP3 D1 AAT2554IRN-T1 GRM188R60J475KE19 GRM188R61A225KE34 GRM1886R1H101JZ01J CDRH2D09-3R0 Chip Resistor Chip Resistor Chip Resistor Chip Resistor Chip Resistor PRPN401PAEN CMD15-21SRC/TR8 Total Power Solution for Portable Applications CER 4.7µF 6.3V X5R 0603 CER 2.2µF 10V X5R 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 100kΩ, 5%, 1/8W; 0402 Connecting Header, 2mm zip Red LED; 1206 AnalogicTech Murata Murata Murata Sumida Vishay Vishay Vishay Vishay Vishay Sullins Electronics Chicago Miniature Lamp Table 5: AAT2554 Evaluation Board Component Listing. 2554.2007.01.1.2 27 AAT2554 Total Power Solution 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 = IRMS = 3 · ΔILOAD 3 · 0.2A = = 4µF (use 4.7µF) 0.1V · 1.5MHz VDROOP · FS 1 2· 3 · (VO) · (VIN(MAX) - VO) 1 1.8V · (4.2V - 1.8V) · = 66mArms = L1 · FS · VIN(MAX) 2 · 3 3.0µH · 1.5MHz · 4.2V Pesr = esr · IRMS2 = 5mΩ · (66mA)2 = 21.8µW 28 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Input Capacitor Input Ripple VPP = 25mV CIN = IRMS = 1 ⎛ VPP ⎞ - ESR · 4 · FS ⎝ IO ⎠ = 1 = 1.38µF (use 4.7µF) ⎛ 25mV ⎞ - 5mΩ · 4 · 1.5MHz ⎝ 0.2A ⎠ IO = 0.1Arms 2 P = esr · IRMS2 = 5mΩ · (0.1A)2 = 0.05mW AAT2554 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 2554.2007.01.1.2 29 AAT2554 Total Power Solution for Portable Applications Output Voltage VOUT (V) Ω R3 = 59kΩ Ω) R2 (kΩ Ω1 R3 = 221kΩ Ω) R2 (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 0 19.6 29.4 39.2 49.9 59.0 68.1 78.7 88.7 118 124 137 187 267 0 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 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. 30 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Manufacturer Murata Murata Murata Murata Murata Murata Part Number Value (µF) Voltage Rating Temp. Co. Case Size 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. 2554.2007.01.1.2 31 AAT2554 Total Power Solution for Portable Applications Ordering Information Package Marking1 Part Number (Tape and Reel)2 TDFN34-16 TDFN34-16 TDFN34-16 TDFN34-16 RZXYY VHXYY SAXYY TOXYY AAT2554IRN-CAP-T1 AAT2554IRN-CAQ-T1 AAT2554IRN-CAT-T1 AAT2554IRN-CAW-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. 32 2554.2007.01.1.2 AAT2554 Total Power Solution for Portable Applications Package Information1 TDFN34-16 3.00 ± 0.05 Detail "A" 4.00 ± 0.05 Index Area 0.35 ± 0.10 Top View 0.23 ± 0.05 Bottom View (4x) 0.45 ± 0.05 0.85 MAX Pin 1 Indicator (optional) 0.05 ± 0.05 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. 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 2554.2007.01.1.2 33