AMS1073 DESCRIPTION FEATURES The AMS1073 is a monolithic step-down switch mode converter with a built-in power MOSFET. It achieves 1.2A peak output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. • • • • • • • • • • • The AMS1073 requires a minimum number of readily available standard external components. The AMS1073 is available in SOT23-6 packages. 1.2A Peak Output Current 0.35Ω Internal Power MOSFET Switch Stable with Low ESR Output Ceramic Capacitors Up to 92% Efficiency 0.1μA Shutdown Mode Fixed 1.4MHz Frequency Thermal Shutdown Cycle-by-Cycle Over Current Protection Wide 4.5V to 24V Operating Input Range Output Adjustable from 0.81V to 15V Available in SOT23-6 Packages APPLICATIONS • • • • Distributed Power Systems Battery Charger Pre-Regulator for Linear Regulators WLED Drivers TYPICAL APPLICATION 5 VIN IN BST 1 C2 10nF 12V C1 10uF AMS1073 OFF ON 4 EN GND 2 SW 6 D1 B230A FB L1 4.7uH VOUT 3.3V @ 1.2A R1 49.9K 3 C3 22uF R2 16.2K 1 Advanced Monolithic Systems http://www.ams-semitech.com AMS1073 ORDERING INFORMATION Part Number AMS1073 Package SOT23-6 Top Marking Free Air Temperature (TA) -40°C to +85°C PACKAGE REFERENCE TOP VIEW BST 1 6 SW GND 2 5 IN FB 3 4 EN ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply Voltage VIN ............................-0.3V~ 26V VSW ............................................-0.3V~Vin+0.3V VBS ....................................................... VSW + 6V All Other Pins ..................................-0.3V to +6V Continuous Power Dissipation (TA = +25°C) (2) SOT23-6 .............................................. 0.568W θJC Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ(MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD(MAX)=(TJ(MAX)TA)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device function is not guaranteed outside of the recommended operating conditions. 4) Measured on JESD51-7, 4-layer PCB.. (3) Supply Voltage VIN ...........................4.5V to 24V Output Voltage VOUT .......................0.81V to 15V Ambient Temperature ................ -40°C to +85°C Max input current into the EN pin............. 300μA 2 Advanced Monolithic Systems θJA SOT23-6 .............................. 220 .... 110.. °C/W Junction Temperature ...............................150°C Lead Temperature ....................................260°C Storage Temperature............... -65°C to +150°C Recommended Operating Conditions (4) http://www.ams-semitech.com AMS1073 ELECTRICAL CHARACTERISTICS VIN = 12V, TA = +25°C, unless otherwise noted. Parameters Symbol Condition Feedback Voltage VFB Feedback Current Switch-On Resistance (5) Switch Leakage Current Limit (5) Oscillator Frequency Fold-back Frequency Maximum Duty Cycle Minimum On-Time (5) Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis EN Input Low Voltage EN Input High Voltage IFB 4.5V ≤ VIN ≤ 24V VFB = 0.8V Typ Max Units 0.790 0.810 0.830 V 0.1 0.35 RDS(ON) VEN = 0V, VSW = 0V fSW VFB = 0.6V VFB = 0V VFB = 0.6V 10 1.2 tON 2.5 1.8 1.4 460 87 100 2.8 150 1.7 3.1 0.4 1.2 VEN = 2V VEN = 0V VEN = 0V VEN = 2V, VFB = 1V EN Input Current Supply Current (Shutdown) Supply Current (Quiescent) Thermal Shutdown (5) Min IS IQ 2.1 0.1 0.1 0.8 150 μA Ω μA A MHz kHz % ns V mV V V μA 1.0 1.0 μA mA °C Note: 5) Guaranteed by design. PIN FUNCTIONS Pin # Name Description 1 BST 2 GND 3 FB 4 EN 5 IN 6 SW Bootstrap. A capacitor is connected between SW and BS pins to form a floating supply across the power switch driver. This capacitor is needed to drive the power switch’s gate above the supply voltage. Ground. This pin is the voltage reference for the regulated output voltage. For this reason care must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to prevent switching current spikes from inducing voltage noise into the part. Feedback. An external resistor divider from the output to GND, tapped to the FB pin sets the output voltage. To prevent current limit run away during a short circuit fault condition, the frequency foldback comparator lowers the oscillator frequency when the FB voltage is below 250mV. On/Off Control Input. Pull EN above 1.2V to turn the device on. For automatic enable, connect a 100kΩ resistor between this pin and Vin pin. Supply Voltage.The AMS1073 operates from a +4.5V to +24V unregulated input.C1 is needed to prevent large voltage spikes from appearing at the input. Switch Output. 3 Advanced Monolithic Systems http://www.ams-semitech.com AMS1073 Functional Block Diagram IN 5 RAMP GENERATOR EN 4 REGULATOR D REGULATOR OSCILLATOR 1.4MHz/460KHz S + -- FB 3 Q R 27pF + -- +EA -- ERROR AMPLIFIER PWM COMPARATOR GND 2 4 Advanced Monolithic Systems DRIVER 1 BST 6 SW M1 R CURRENT LIMIT COMPARATOR 1pF REFERENCE CURRENT SENSE AMPLIFIER + -- x20 http://www.ams-semitech.com AMS1073 TYPICAL APPLICATION CIRCUITS D3 1N4148 (Optional) VIN 5 C1 10uF IN BS 1 C2 10nF 4 OFF ON Notes: 1) D3 can be installed if VIN < 5V 2) D2 can be installed if VOUT < 5V 3) No need for both D2 and D3 EN AMS1073 GND SW 6 D2 1N4148 (Optional) L1 4.7uH C3 22uF D1 FB U1 VOUT 3.3V 3 R2 16.2K R1 49.9K Vout=0.81X(1+R1/R2) 1.4MHz, 3.3V Output at 1A Step-Down Converter Resistor Selection for Common Output Voltages VOUT (V) R1 (kΩ) R2 (kΩ) 1.8 2.5 3.3 5 80.6 (1%) 49.9 (1%) 49.9 (1%) 49.9 (1%) 64.9 (1%) 23.7 (1%) 16.2 (1%) 9.53 (1%) 5 Advanced Monolithic Systems http://www.ams-semitech.com AMS1073 SOT23-6 MILLIMETER SYMBOL MIN NOR MAX A - - 1.35 A1 0.04 - 0.15 A2 1.00 1.10 1.20 A3 0.55 0.65 0.75 D 2.72 2.92 3.12 E 2.60 2.80 3.0 E1 1.40 1.60 1.80 e 0.95BSC e1 1.90BSC L 0.30 - 0.60 θ 0 - 8° 6 Advanced Monolithic Systems http://www.ams-semitech.com