Datasheet LTC3448 (Analog Devices) - 6

LTC3448
W U TYPICAL PERFOR A CE CHARACTERISTICS (From Figure 1a Except for the Resistive Divider Resistor Values) External Mode Control (Constant Load Step 1mA Load)
SWITCHER SWITCHER V VOUT OUT LDO 100mV/DIV 20mV/DIV AC COUPLED AC COUPLED ILOAD 250mA/DIV MODE PIN 2V/DIV IL 500mA/DIV VIN = 3.6V 10µs/DIV 3448 G18 VOUT = 1.5V 200µs/DIV 3448 G19 VOUT = 1.5V TA = 25°C ILOAD = 100mA TO 600mA
U U U PI FU CTIO S VFB (Pin 1):
Feedback Pin. This pin receives the feedback
VIN (Pin 4):
Main Supply Pin. This pin must be closely voltage from an external resistive divider across the decoupled to GND with a 2.2µF or greater ceramic output. capacitor.
VOUT (Pin 2):
Output Pin. This pin connects to an external
SW (Pin 5):
Switch Node Connection to Inductor. This pin resistor divider and the linear regulator output. Connect connects to the drains of the internal main and synchro- externally to the inductor and the output capacitor. The nous power MOSFET switches. internal linear regulator will supply current up to the
FREQ (Pin 6):
Frequency Select. Switching frequency is ILDO(OFF) current. Load currents above that are supplied by set to 1.5MHz when FREQ = 0V and to 2.25MHz when the buck regulator. Internal circuitry automatically enables FREQ = V the buck switching regulator at load currents higher than IN. Do not float this pin. the I
SYNC (Pin 7):
External Synchronization Pin. The oscilla- LDO(OFF). The minimum required capacitance on this pin is 2µF. tion frequency can be synchronized to an external oscilla- tor applied to this pin. For external frequencies above
MODE (Pin 3):
Linear Regulator Control. Grounding this 2.2MHz, pull FREQ high. pin turns off the linear regulator. Setting this pin to VIN turns on the linear regulator regardless of the load current.
RUN (Pin 8):
Run Control Input. Forcing this pin above Tying this pin midrange (i.e., to V 1.5V enables the part. Forcing this pin below 0.3V shuts OUT) will place the linear regulator in auto mode, where turn on/off is a function of down the device. In shutdown, all functions are disabled the load current. In applications where MODE is externally drawing <1µA supply current. Do not leave RUN floating. driven high or low, this pin should be held low for 50µs
Exposed Pad (Pin 9):
Ground. This pin must be soldered after the RUN pin is pulled high. to PCB. 3448f 6