Typical Application Circuit (continued)
Figure2. 24V to 3.3V/5V Application Circuit
PIN PIN NAME
9 (Exposed Pad)
High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel
DMOS switch. Connect a 0.01µF or greater capacitor from SW to BS to power the high
Input Supply Pin. IN supplies the power to the IC, as well as the step-down converter
switches. Drive IN with a 4.5V to 30V power source. Bypass IN to GND with a suitably
large capacitor to minimize input ripple to the IC. See Input Capacitor Section of the
Power Switching Output. Connect the output LC filter from SW to the output load.
Ground. GND pin should be connected to the exposed thermal pad for proper operation.
This power thermal pad should be connected to PCB ground plane using multiple vias
for good thermal performance.
Output Feedback Input. FB senses the output voltage and regulates it. Drive FB with a
resistive voltage divider connected to it from the output voltage. The feedback threshold
is 0.925V. See Setting the Output Voltage.
Loop compensation Input. Connect a series RC network from COMP to GND to
compensate the regulation control loop. See Compensation.
Enable Input. EN is a logic input that controls the regulator on or off. Drive EN high to
turn on the regulator; low to turn it off. Don’t leave EN pin floating. Directly connect
EN to IN (or through a resistance) for automatic startup.
Soft-Start Control Input. Connect an external capacitor to program the soft-start. If
unused, leave it open, which means internal soft-start function.
DS3484 Ver1.4 May 2012