AS1324 1.5MHz, 600mA Synchronous DC/DC Converter 1 General Description 2 Key Features High Efficiency: Up to 96% The AS1324 is a high-efficiency, constant-frequency synchronous buck converter available in adjustable- and fixed-voltage versions. Output Current: 600mA The wide input voltage range (2.7V to 5.5V), automatic powersave mode and minimal external component requirements make the Input Voltage Range: 2.7V to 5.5V AS1324 perfect for any single Li-Ion battery-powered application. Typical supply current with no load is 30A and decreases to 1A Constant Frequency Operation: 1.5MHz in shutdown mode. Variable- and Fixed-Output Voltages The AS1324 is available as the standard versions listed in Table 1. Table 1. Standard Versions No Schottky Diode Required Model Output Voltage Automatic Powersave Operation AS1324-AD Adjustable via External Resistors Low Quiescent Current: 30A AS1324-12 Fixed: 1.2V Internal Reference: 0.6V AS1324-15 Fixed: 1.5V AS1324-18 Fixed: 1.8V Shutdown Mode Supply Current: 1A Thermal Protection An internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. The internally fixed 5-pin TSOT-23 Package switching frequency (1.5MHz) allows for the use of small surface mount external components. Very low output voltages can be delivered with the internal 0.6V 3 Applications feedback reference voltage. The AS1324 is available in a 5-pin TSOT-23 package. The device is ideal for mobile communication devices, laptops and PDAs, ultra-low-power systems, threshold detectors/discriminators, telemetry and remote systems, medical instruments, or any other space-limited application with low power-consumption requirements. Figure 1. Typical Application Diagram High Efficiency Step Down Converter 4.7H VOUT = 1.8V, 600mA VIN = 2.7V to 5.5V 4 3 EN 1 5 VOUT VIN SW CIN COUT 10F 10F AS1324-18 AS1324-18 GND 2 1 5 EN VOUT SW 3 4 VIN GND 2 www.ams.com/DC-DC Step-Up/AS1324 Revision 1.06 1 - 21AS1324 Datasheet - P in A s s ig n me nt s 4 Pin Assignments Figure 2. Pin Assignments (Top View) EN EN 1 5 VFB 1 5 VOUT AS1324-12/ AS1324 AS1324-15/ GND 2 GND 2 AS1324-18 SW 3 4 VIN SW 3 4 VIN 4.1 Pin Descriptions Table 2. Pin Descriptions Pin Number Pin Name Description Enable Input. Driving this pin above 1.5V enables the device. Driving this pin below 0.3V puts the device in shutdown mode. In shutdown mode all functions are disabled while SW goes high 1 EN impedance, drawing <1A supply current. Note: This pin should not be left floating. 2 GND Ground. Switch Node Connection to Inductor. This pin connects to the drains of the internal main and 3 SW synchronous power MOSFET switches. Input Supply Voltage. This pin must be closely decoupled to GND with a 4.7F ceramic capacitor. 4 VIN Connect to any supply voltage between 2.7 to 5.5V. Feedback Pin. This pin receives the feedback voltage from the external resistor divider across the VFB output. (Adjustable voltage variant only.) 5 Output Voltage Feedback Pin. An internal resistor divider steps the output voltage down for VOUT comparison to the internal reference voltage. (Fixed voltage variants only.) www.ams.com/DC-DC Step-Up/AS1324 Revision 1.06 2 - 21