LTC3549 UUUPI FU CTIO SVIN (Pin 1): Main Supply Pin. Must be closely decoupled RUN (Pin 5): Run Control Input. Forcing this pin above 1.1V to GND, Pins 2 and 7, with a 4.7µF or greater ceramic enables the part. Forcing this pin below 0.3V shuts down capacitor. the device. In shutdown, all functions are disabled drawing <1µA supply current. Do not leave RUN fl oating. GND (Pin 2): N/C. Ground this pin. VSW (Pin 3): Switch Node Connection to Inductor. This pin FB (Pin 6): Feedback Pin. Receives the feedback voltage from an external resistive divider across the output. connects to the drains of the internal main and synchronous power MOSFET switches. GND (Pin 7): Exposed Pad. The Exposed Pad is ground. It must be soldered to PCB ground to provide both electrical MODE (Pin 4): Mode Select Input. To select pulse-skip- contact and optimum thermal performance. ping mode, force this pin above 1.1V. Forcing this pin below 0.3V selects Burst Mode operation. Do not leave MODE fl oating. UUWFU CTIO AL DIAGRA MODE 4 SLOPE COMP 0.65V OSCILLATOR OSC 1 VIN – VFB EN + – 6 SLEEP + 0.611V 5Ω – 0.4V + – + I EA COMP BURST S Q SOFT- R Q START SWITCHING RS LATCH LOGIC VIN AND ANTI- BLANKING SHOOT- THRU 3 SW RUN CIRCUIT + 5 REFERENCE OV OVDET 0.671 – + SHUTDOWN IRCMP– 2 GND 7 GND 3549 FD 3549f 7