AMS1076 DESCRIPTION FEATURES The AMS1076 is a monolithic integrated stepdown switch mode converter with an internal power MOSFET. It achieves 1A continuous 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 AMS1076 requires a minimum number of readily available standard external components. The AMS1076 is available in SOT23-6 packages. 1A Output Current 0.45Ω 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 18V Operating Input Range Output Adjustable from 0.81V to 15V Available in SOT23-6 Packages APPLICATIONS • • • Hand Disk Drive xDSL Modems Cable Set-Top Box TYPICAL APPLICATION VIN 5 IN BST 1 12V CB 10nF AMS1076 OFF ON 4 EN GND SW VOUT 3.3V @ 1A 6 D1 B230A FB 3 2 Vout=0.81x(1+R1/R2) (V) 1 Advanced Monolithic Systems http://www.ams-semitech.com AMS1076 PACKAGE REFERENCE TOP VIEW BST 1 6 SW GND 2 5 IN FB 3 4 EN SOT23-6 ABSOLUTE MAXIMUM RATINGS Supply Voltage VIN .............................-0.3V~21V VSW .............................................-0.3V~Vin+0.3V VBS ....................................................... VSW ~ 6V All Other Pins .................................–0.3V ~ +6V Lead Temperature ....................................260°C Storage Temperature.............. –65°C to +150°C Recommended Operating Conditions Supply Voltage VIN ...........................4.5V to 18V Output Voltage VOUT ......................... 0.81 to 15V Operation Temperature .............–40°C ~ +85°C 2 Advanced Monolithic Systems http://www.ams-semitech.com AMS1076 ELECTRICAL CHARACTERISTICS VIN = 12V, TA = +25°C, unless otherwise noted. Parameters Symbol Condition Feedback Voltage VFB Feedback Current IFB Switch-On Resistance Switch Leakage 4.5V ≤ VIN ≤ 18V VFB = 0.8V VFB = 2V Min Typ Max Units 0.790 0.810 0.830 V 10 nA µA Ω μA 10 2 0.45 RDS(ON) VEN = 0V, VSW = 0V Current Limit 1.8 Oscillator Frequency Fold-back Frequency Maximum Duty Cycle Minimum On-Time Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis EN Input Low Voltage En Input High Voltage fSW 1.2 VFB = 0V VFB = 0.6V tON 2.5 1.4 460 87 100 2.8 150 A 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 2.1 0.1 0.1 0.8 160 MHz KHz % ns V mV V V μA 1 1 μA mA °C PIN FUNCTIONS Pin # Name Description 1 BST 2 GND 3 FB 4 EN 5 IN 6 SW Bootstrap. This capacitor is needed to drive the power switch’s gate above the supply voltage. It is connected between SW and BS pins to form a floating supply across the power switch driver. 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 above 1.2V to turn the device on. Supply Voltage. The AMS1076 operates from a +4.5V to +18V 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 AMS1076 Functional Block Diagram CURRENT SENSE AMPLIFIER Enable Reference Rsen Offset CURRENT LIMIT COMPARATOR ERROR AMPLIFIER REGULATOR PWM COMPARATOR OTP LVP 4 Advanced Monolithic Systems http://www.ams-semitech.com AMS1076 SOT23-6 2.80 3.00 6 4 1.50 1.70 2.60 3.00 0.09 0.20 1 3 SIDE VIEW TOP VIEW 0.90 1.30 1.45 MAX SEATING PLANE 0.30 0.50 0.95 BSC 0.00 0.15 NOTE: ALL DIMENSIONS ARE IN MILLIMETERS . FRONT VIEW 5 Advanced Monolithic Systems http://www.ams-semitech.com