AAT2786IRN-AE-T1

PRODUCT DATASHEET AAT2786 SystemPowerTM General Description The AAT2786 is a dual output power solution. It includes a 1.5A, 1.4MHz, high-efficiency step-down converter and a high performance 150mA LDO regulator. The stepdown regulator output voltage is adjustable from 0.6V to VIN. The LDO regulator has a factory preset fixed output voltage from 1.2V to 3.3V. The step-down converter consumes only 42µA of no-load quiescent current and is designed to maintain high efficiency throughout the load range. The step-down converter has ultra-low RDS(ON) integrated MOSFETs and can operate up to 100% duty cycle to enable high output voltage, high current applications which require a low dropout threshold. The AAT2786 provides excellent transient response and high output accuracy across the operating range. Pulling the MODE/SYNC pin high enables “PWM Only” mode, maintaining constant frequency and low output ripple across the operating range. Alternatively, the converter may be synchronized to an external clock input via the MODE/SYNC pin. The MicroPower low dropout linear regulator in the AAT2786 has been specifically designed for high-speed turn-on and turn-off performance, fast transient response, and good noise and power supply ripple rejection (PSRR), making it ideal for powering sensitive circuits with fast switching requirements. Over-temperature and short-circuit protection safeguard the AAT2786 and system components from damage. 1.5A Step-Down Converter and 150mA LDO Features • VIN Range : 2.5V to 5.5V • 1.5A Step-Down Converter ▪ VOUT Range: 0.6V to VIN ▪ 95% Peak Efficiency ▪ High Efficiency across load range ▪ 42µA No Load Quiescent Current ▪ Optional “PWM Only” Low Noise Mode ▪ Current limit and soft start • 150mA LDO Regulator ▪ VOUT Range: 1.2V to 3.3V (Fixed) ▪ High Power Supply Rejection Ratio ▪ Low Output Noise • Independent Enable Pins • Integrated Power MOSFETs • Over-Temperature Protection • TDFN34-16 Package • -40°C to +85°C Temperature Range Applications • • • • • Cellular and Smart Phones PDAs, Palmtops Digital Still and Video Cameras Portable Instruments Battery-Powered Applications Typical Application U1 BUCK IN R1 100 C1 opt C2 10µF C3 1µF ON/OFF ON/OFF LDO IN ON/OFF C6 1µF C8 10nF 16 15 12 L1 LX LX FB 1 VP VP VIN BUCK_EN MODE/SYNC LDOIN LDO_EN BYP BUCK OUT 3.3µH R2 Adj C5 Opt 2 5 C4 22µF 13 14 AAT2786IRN GND 4 R3 59k 11 9 8 LDO_OUT 6 LDO OUT PGND 3 C7 2.2µF 7 10 N/C LDO_GND 2786.2008.04.1.0 www.analogictech.com 1 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM Pin Descriptions Pin # 1, 2 3 4 5 6 7 8 9 10 11 12 13 14 15,16 1.5A Step-Down Converter and 150mA LDO Symbol LX PGND GND FB LDOOUT LDO_GND BYP LDO_EN N/C LDOIN VIN BUCK_EN MODE/SYNC VP Description Step-down converter switching node. Connect the output inductor to this pin. The switching node is internally connected to the drain of both high- and low-side MOSFETs. Step-down converter main power ground return pin. Connect to the output and input capacitor return. Non-power signal ground pin. Step-down converter feedback input pin. This pin is connected either directly to the converter output or to an external resistive divider for an adjustable output. LDO output pin; should be decoupled with 2.2µF ceramic capacitor. LDO ground connection pin. LDO bypass capacitor connection; to improve AC ripple rejection, connect a 10nF capacitor to GND. This will also provide a soft start function. LDO enable pin; this pin should not be left floating. When pulled low, the LDO PMOS pass transistor turns off and all internal circuitry enters low-power mode, consuming less than 1µA. Open LDO input voltage pin; should be decoupled with 1µF or greater capacitor. Step-down converter power supply. Supplies power for the internal circuitry. Step-down converter enable pin. A logic low disables the step-down converter and it consumes less than 1µA of current. When connected high, it resumes normal operation. Connect to ground for Light-Load/PWM mode and optimized efficiency throughout the load range. Connect high for low noise PWM operation under all operating conditions. Connect to an external clock for synchronization (PWM only). Step-down converter input voltage for the power switches. Pin Configuration TDFN34-16 (Top View) LX LX PGND GND FB LDOOUT LDO_GND BYP 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VP VP MODE/SYNC BUCK_EN VIN LDOIN N/C LDO_EN 2 www.analogictech.com 2786.2008.04.1.0 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM Absolute Maximum Ratings TA = 25°C unless otherwise noted. Symbol VIN VLX VFB VN VLDOIN VENIN(MAX) TJ TLEAD 1.5A Step-Down Converter and 150mA LDO Description VIN, VP to GND LX Pin to GND FB Pin to GND MODE/SYNC, BUCK_EN to GND VLDOIN to LDO_GND LDO_EN to LDO_GND Maximum Junction Operating Temperature Maximum Soldering Temperature (at leads, 10 sec) Value 6.0 -0.3 to VIN + 0.3 -0.3 to VIN + 0.3 -0.3 to 6.0 6.0 -0.3 to VIN + 0.3 -40 to +150 300 Units V °C Thermal Information Symbol PD θJA VLDOIN Description Maximum Power Dissipation1 Thermal Resistance LDO Input Voltage Value 2.0 50 + VDO) to 5.5 Units W °C/W V (VLDOUT 1. Derate 20mW/ºC above 25°C ambient temperature. 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. 2. Mounted on an FR4 board. 3. To calculate minimum input voltage, use the following equation: VIN(MIN) = VOUT(MAX) + VDO(MAX) as long as VIN ≥ 2.5V. 2786.2008.04.1.0 www.analogictech.com 3 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM Electrical Characteristics1 1.5A Step-Down Converter and 150mA LDO VIN=3.6V; TA = -40oC to 85oC unless otherwise noted. Typical values are at TA = 25oC. Symbol Description Conditions Min 2.5 0.6 VIN Rising Hysteresis VIN Falling IOUT = 0A to 1.5A, VIN = 2.4V to 5.5V No Load VEN = GND 150 1.7 -3.0 42 1.8 0.120 0.085 VIN = 5.5V, VLX = 0 to VIN ILOAD = 0A to 1.5A VIN = 2.4V to 5.5V No Load, TA = 25°C VOUT = 1.0V TA = 25°C From Enable to Output Regulation 1.12 0.60 1.4 150 140 15 0.6 1.4 VIN = VEN = 5.5V 1.0 0.591 1.0 0.5 0.2 0.60 0.609 0.2 1.68 3.0 3.0 90 1.0 Typ Max 5.5 Units V V Step-Down Converter VIN Input Voltage VOUT Output Voltage Range VUVLO VOUT IQ ISHDN ILIM RDS(ON)H RDS(ON)L ILXLEAK ΔVLOADREG ΔVLINEREG/ ΔVIN VFB UVLO Threshold Output Voltage Tolerance Quiescent Current Shutdown Current Current Limit High Side Switch On-Resistance Low Side Switch On-Resistance LX Leakage Current Load Regulation Line Regulation VIN 2.5 V mV V % µA µA A Ω Ω µA % %/V V µA MHz µs °C °C V V µA Feedback Threshold Voltage Accuracy (Adjustable Version) IFB FB Leakage Current Internal Oscillator Frequency FOSC Synchronous Clock Start-Up Time TS TSD Over-Temperature Shutdown Threshold THYS Over-Temperature Shutdown Hysteresis MODE/SYNC VMODE/SYNC(L) Enable Threshold Low VMODE/SYNC(H) Enable Threshold High IMODE/SYNC Enable Leakage Current 1. The AAT2786 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. 4 www.analogictech.com 2786.2008.04.1.0 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM 1.5A Step-Down Converter and 150mA LDO Electrical Characteristics (continued) VLDOIN = VOUT(NOM) + 1V for VOUT options greater than 1.5V. VIN = 2.5 for VOUT ≤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 VLDOOUT ILDOOUT VDO ISC IQ ISD ΔVOUT/ VOUT*ΔVIN ΔVOUT(line) ΔVOUT(load) PSRR eN TSD THYS TC Enable VIL VIH IEN_BUCK IEN_LDO tENDLY Description Output Voltage Tolerance Output Current Dropout Voltage2, 3 Short-Circuit Current Ground Current Shutdown Current Line Regulation Dynamic Line Regulation Dynamic Load Regulation Power Supply Rejection Ratio Output Noise Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis Output Voltage Temperature Coefficient Enable Enable Enable Enable Enable Threshold Low Threshold High Leakage Current Leakage Current Delay Time Conditions TA = 25°C ILDOOUT = 1mA to 150mA TA = -40°C to 85°C VLDOOUT > 1.2V ILDOOUT = 150mA VLDOOUT < 0.4V VIN = 5V, No Load, EN = VIN VIN = 5V, EN = 0V VIN = VOUT + 1 to 5.0V VIN = VLDOOUT + 1V to VLDOOUT + 2V, ILDOOUT = 150mA, TR/TF = 2µs ILDOOUT = 1mA to 150mA, TR < 5µs 1 kHz ILDOOUT = 10mA, 10kHz CBYP = 10nF 1MHz Noise Power BW = 300Hz - 50kHz Min -1.5 -2.5 150 Typ Max 1.5 2.5 Units % mA mV mA µA µA %/V mV mV dB µVrms °C °C ppm/°C LDO Regulator 200 600 70 300 125 1 0.09 2.5 30 67 47 45 50 145 12 22 0.6 1.4 VEN_BUCK = 5V VEN_LDO = 5V BYP = Open 1 1.0 15 V V µA µA µs 1. VDO is defined as VLDOIN - VLDOOUT when VLDOOUT is 98% of nominal. 2. For VLDOOUT < 2.3V, VDO = 2.5V - VLDOOUT. 2786.2008.04.1.0 www.analogictech.com 5 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM 1.5A Step-Down Converter and 150mA LDO Typical Characteristics–Step-Down Converter Efficiency vs. Output Current (Light-Load Mode; VOUT = 3.3V) 100 0.50 Load Regulation (Light-Load Mode; VOUT = 3.3V) VIN = 3.6V 90 Efficiency (%) 80 70 60 50 40 0.1 VIN = 4.2V VIN = 5.0V VOUT Error (%) 0.25 VIN = 3.6V VIN = 4.2V 0.00 -0.25 VIN = 5.0V 1 10 100 1000 10000 -0.50 0.1 1 10 100 1000 10000 Output Current (mA) Output Current (mA) Efficiency vs. Output Current (PWM Mode; VOUT = 3.3V) 100 0.50 Load Regulation (PWM Mode; VOUT = 3.3V) VIN = 3.6V 80 Efficiency (%) 60 40 20 0 1.0 VIN = 5.0V VIN = 4.2V VOUT Error (%) 0.25 VIN = 3.6V VIN = 5.0V 0.00 VIN = 4.2V -0.25 10 100 1000 10000 -0.50 0.1 1 10 100 1000 10000 Output Current (mA) Output Current (mA) Efficiency vs. Output Current (Light-Load Mode; VOUT = 2.5V) 100 0.50 Load Regulation (Light-Load Mode; VOUT = 2.5V) VIN = 2.7V 90 Efficiency (%) 80 VIN = 3.6V 70 60 50 0.1 1 10 VIN = 4.2V VOUT Error (%) 0.25 VIN = 2.7V VIN = 3.6V 0.00 -0.25 VIN = 4.2V 100 1000 10000 -0.50 0.1 1 10 100 1000 10000 Output Current (mA) Output Current (mA) 6 www.analogictech.com 2786.2008.04.1.0 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM 1.5A Step-Down Converter and 150mA LDO Typical Characteristics–Step-Down Converter Efficiency vs. Output Current (PWM Mode; VOUT = 2.5V) 100 90 80 100 Efficiency vs. Output Current (PWM Mode; VOUT = 2.5V) 90 80 VIN = 2.7V Efficiency (%) VIN = 2.7V Efficiency (%) 70 60 50 40 30 20 10 0 1 70 60 50 40 30 20 10 0 VIN = 5.0V VIN = 4.2V VIN = 3.6V 10 100 1000 10000 VIN = 5.0V VIN = 4.2V VIN = 3.6V 1 10 100 1000 10000 Output Current (mA) Output Current (mA) Efficiency vs. Output Current (Light-Load Mode; VOUT = 1.8V) 100 90 0.50 Load Regulation (Light-Load Mode; VOUT = 1.8V) VIN = 2.7V VOUT Error (%) 0.25 Efficiency (%) 80 70 60 50 40 0.1 VIN = 3.6V VIN = 2.7V VIN = 3.6V VIN = 4.2V 0.00 -0.25 VIN = 4.2V 1 10 100 1000 10000 -0.50 0.1 1 10 100 1000 Output Current (mA) Output Current (mA) Efficiency vs. Output Current (PWM Mode; VOUT = 1.8V) 100 90 80 0.50 Load Regulation (PWM Mode; VOUT = 1.8V) Efficiency (%) 70 60 50 40 30 20 10 0 1 10 VIN = 4.2V VOUT Error (%) VIN = 2.7V 0.25 VIN = 2.7V VIN = 3.6V 0.00 VIN = 3.6V -0.25 VIN = 4.2V 100 1000 10000 -0.50 0.1 1 10 100 1000 10000 Output Current (mA) Output Current (mA) 2786.2008.04.1.0 www.analogictech.com 7 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM 1.5A Step-Down Converter and 150mA LDO Typical Characteristics–Step-Down Converter Efficiency vs. Output Current (Light-Load Mode; VOUT = 1.2V) 100 90 0.50 Load Regulation (Light-Load Mode; VOUT = 1.2V) VIN = 2.7V VOUT Error (%) 0.25 Efficiency (%) 80 70 60 50 40 30 0.1 1 10 100 1000 10000 VIN = 2.7V VIN = 3.6V VIN = 3.6V VIN = 4.2V 0.00 -0.25 VIN = 4.2V -0.50 0.1 1 10 100 1000 10000 Output Current (mA) Output Current (mA) Efficiency vs. Output Current (PWM Mode; VOUT = 1.2V) 100 90 80 0.50 Load Regulation (PWM Mode; VOUT = 1.2V) VIN = 2.7V VIN = 4.2V VIN = 3.6V VOUT Error (%) Efficiency (%) 70 60 50 40 30 20 10 0 1 10 100 0.25 VIN = 2.7V VIN = 3.6V 0.00 -0.25 VIN = 4.2V 1000 10000 -0.50 0.1 1 10 100 1000 10000 Output Current (mA) Output Current (mA) Output Voltage vs. Temperature (VIN = 3.6V; VOUT = 1.8V; IOUT = 1A) Output Voltage Change (%) 1.0 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 -40 -20 0 20 40 60 80 70 0.8 65 60 55 50 45 40 35 30 2.7 Supply Current vs. Supply Voltage (VOUT = 1.8V; No Load; Light-Load Mode) Supply Current (µA) 85°C 25°C -40°C 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Temperature (°C) Supply Voltage (V) 8 www.analogictech.com 2786.2008.04.1.0 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM 1.5A Step-Down Converter and 150mA LDO Typical Characteristics–Step-Down Converter Switching Frequency vs. Temperature (VIN = 3.6V; VOUT = 1.8V; IOUT = 1A) Switching Frequency (MHz) Output Voltage Error (%) 1.40 1.38 1.36 1.34 1.32 1.30 1.28 1.26 1.24 -40 -20 0 20 40 60 80 0.12 0.10 0.08 0.06 0.04 0.02 0.00 -0.02 -0.04 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 Line Regulation (VOUT = 1.8V; IOUT = 1A) Temperature (°C) Supply Voltage (V) Switching Frequency vs. Input Voltage (IOUT = 1A) Switching Frequency (MHz) 1.40 1.39 1.38 1.37 1.36 1.35 1.34 1.33 1.32 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 Enable Soft Start (VOUT = 3.6V; IOUT = 1.5A) VOUT = 1.8V VOUT = 2.5V EN (2V/div) VOUT (1V/div) IIN (500mA/div) Time (100µs/div) VOUT = 3.3V Input Voltage (V) P-Channel RDS(ON) vs. Input Voltage 180 170 160 150 N-Channel RDS(ON) vs. Input Voltage 120°C RDS(ON) (mΩ) 140 130 120 110 100 90 80 70 60 120°C RDS(ON) (mΩ) 150 140 130 120 110 100 90 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 85°C 25°C 85°C 25°C 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 Input Voltage (V) Input Voltage (V) 2786.2008.04.1.0 www.analogictech.com 9 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM 1.5A Step-Down Converter and 150mA LDO Typical Characteristics–Step-Down Converter Heavy Load Switching Waveform (PWM Mode; VIN = 3.6V; VOUT = 1.8V; 1.5A Load) Output Voltage (AC coupled) (top) (mV) 4.0 2.0 0.0 -2.0 -4.0 -6.0 -8.0 -10.0 -12.0 2.6 Light Load Switching Waveform (PWM Mode; VIN = 3.6V; VOUT = 1.8V; 1mA Load) Output Voltage (AC coupled) (top) (mV) 4.0 2.0 0.0 -2.0 -4.0 -6.0 -8.0 -10.0 -12.0 1200 Inductor Ripple Current (bottom) (mA) Inductor Ripple Current (bottom) (mA) 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 1000 800 600 400 200 0 -200 -400 Time (2.5µs/div) Time (2.5µs/div) Light Load Switching Waveform (Light-Load Mode; VIN = 3.6V; VOUT = 1.8V; 1mA Load) Output Voltage (AC coupled) (top) (mV) 8.0 4.0 0.0 -4.0 -8.0 -12.0 -16.0 -20.0 -24.0 700 2.5 Load Transient Response (VIN = 3.6V; VOUT = 1.8V; CFF = 100pF) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 Inductor Ripple Current (bottom) (mA) 600 500 400 300 200 100 0 -100 2.0 Output Voltage (top) (V) 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 Load Current (bottom) (A) Time (100µs/div) Time (50µs/div) Load Transient Response (VIN = 3.6V; VOUT = 1.8V; No CFF) 2.5 2.0 3.5 3.0 5.0 4.5 Line Transient Response (VOUT = 1.8V; 1.5A Load) 3.0 2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4 Output Voltage (top) (V) 1.0 0.5 0.0 -0.5 -1.0 -1.5 2.0 1.5 1.0 0.5 0.0 -0.5 Input Voltage (top) (V) 1.5 2.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 Output Voltage (bottom) (V) Load Current (bottom) (A) Time (50µs/div) Time (200µs/div) 10 www.analogictech.com 2786.2008.04.1.0 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM Typical Characteristics–LDO Dropout Voltage vs. Temperature 1.5A Step-Down Converter and 150mA LDO Dropout Characteristics 3.20 260 240 220 200 180 160 140 120 100 80 60 40 20 0 Dropout Voltage (mV) Output Voltage (V) IL = 150mA IL = 100mA 3.00 2.80 2.60 IOUT = 0mA IOUT = 10mA IOUT = 50mA IOUT = 100mA IOUT = 150mA 2.40 2.20 2.00 2.70 IL = 50mA -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 Temperature (°C) 2.80 2.90 3.00 3.10 3.20 Input Voltage (V) Dropout Voltage vs. Output Current 90.00 Ground Current vs. Input Voltage 80.00 70.00 60.00 50.00 40.00 30.00 20.00 10.00 0.00 300 Dropout Voltage (mV) 250 200 150 100 50 0 0 25 50 75 100 125 150 85°C 25°C -40°C Ground Current (µA) IOUT = 150mA IOUT = 0mA IOUT = 50mA IOUT = 10mA 2 2.5 3 3.5 4 4.5 Output Current (mA) Input Voltage (V) Quiescent Current vs. Temperature 100 Output Voltage vs. Temperature 1.203 1.202 Quiescent Current (µA) 90 Output Voltage (V) -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 80 70 60 50 40 30 20 10 0 1.201 1.200 1.199 1.198 1.197 1.196 -40 -30 -20 -10 Temperature (°C) 0 10 20 30 40 50 60 70 80 90 100 Temperature (°C) 2786.2008.04.1.0 www.analogictech.com 11 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM Typical Characteristics–LDO Initial Power-Up Response Time (CBYP = 10nF) VEN (5V/div) 1.5A Step-Down Converter and 150mA LDO Turn-Off Response Time (CBYP = 10nF) VEN (5V/div) VOUT (1V/div) Time (400µs/div) VOUT (1V/div) Time (50µs/div) Turn-On Time From Enable (VIN present) (CBYP = 10nF) 1200 Over-Current Protection VEN (5V/div) Output Current (mA) VOUT (1V/div) Time (5µs/div) 1000 800 600 400 200 0 -200 Time (20ms/div) Line Transient Response 6 3.04 2.90 Load Transient Response 500 VIN Output Voltage (V) Input Voltage (V) 5 4 3 2 1 0 3.03 3.02 3.01 3.00 2.85 2.80 2.75 2.70 2.65 2.60 VOUT 400 300 200 100 0 Output Current (mA) Output Voltage (V) VOUT 2.99 2.98 IOUT Time (100µs/div) -100 Time (100µs/div) 12 www.analogictech.com 2786.2008.04.1.0 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM Typical Characteristics–LDO AAT2786 Self Noise (COUT = 10µF, ceramic) Noise Amplitude (µV/rtHz) 10 1.5A Step-Down Converter and 150mA LDO VIH and V IL vs. VIN 1.250 1.225 1 1.200 1.175 VIH 0.1 Band Power: 300Hz to 50kHz = 44.6µVrms/rtHz 100Hz to 100kHz = 56.3µVrms/rtHz 1.150 1.125 0.01 1.100 1.075 100 1000 10000 1.050 2.5 3.0 3.5 VIL 0.001 0.01 0.1 1 10 4.0 4.5 5.0 5.5 Frequency (kHz) Input Voltage (V) 2786.2008.04.1.0 www.analogictech.com 13 PRODUCT DATASHEET AAT2786 AAT2786 SystemPowerTM Functional Block Diagram 1.5A Step-Down Converter and 150mA LDO VIN Oscillator VP Co ntro l Circ uit LX PGND MODE/SYNC GND FB BUCK_EN Bias LDO_EN LDOIN BYP LDOOUT RLDOFB1 RLDOFB2 LDO_GND Functional Description The AAT2786 is a dual output power solution. It includes a 1.5A, 1.4MHz, high-efficiency step-down converter and a high performance 150mA LDO regulator. The stepdown regulator output voltage is adjustable from 0.6V to VIN. The LDO regulator has a factory preset fixed output voltage from 1.2V to 3.3V. The on and off states of the step-down converter and the LDO regulator are independently controlled by separate enable pins. Step-Down Converter The step-down converter in the AAT2786 is a high performance 1.5A monolithic step-down converter operating at 1.4MHz switching frequency. It minimizes external component size and optimizes efficiency over the complete load range. Apart from the small bypass input capacitor, only a small L-C filter is required at the output. Typically, a 3.3µH inductor and a 22µF ceramic capacitor are recommended for a 3.3V output (see table of recommended values). 14 www.analogictech.com 2786.2008.04.1.0 PRODUCT DATASHEET AAT2786 SystemPowerTM At dropout, the step-down converter duty cycle increases to 100% and the output voltage tracks the input voltage minus the RDS(ON) drop of the P-channel high side MOSFET (plus the DC drop of the external inductor). The device integrates extremely low RDS(ON) MOSFETs to achieve low dropout voltage during 100% duty cycle operation. This is advantageous in applications requiring high output voltages (typically > 2.5V) at low input voltages. The integrated low-loss MOSFET switches can provide greater than 95% efficiency at full load. Light-Load operation maintains high efficiency under light load conditions (typically