Datasheet LT3505 (Analog Devices) - 7

LT3505 PIN FUNCTIONS
BOOST (Pin 1):
The BOOST pin is used to provide a drive
RT (Pin 6):
The RT pin is used to program the switching voltage, higher than the input voltage, to the internal bipolar frequency of the LT3505 by connecting a resistor from NPN power switch. this pin to ground. The Applications Information section of
SW (Pin 2):
The SW pin is the output of the internal power the data sheet includes a table to determine the resistance switch. Connect this pin to the inductor, catch diode and value based on the desired switching frequency. Minimize boost capacitor. capacitance at this pin.
V FB (Pin 7):
The LT3505 regulates its feedback pin to 780mV.
IN (Pin 3):
The VIN pin supplies current to the LT3505’s internal regulator and to the internal power switch. This Connect the feedback resistor divider tap to this pin. Set pin must be locally bypassed. the output voltage by selecting R1 according to:
SHDN (Pin 4):
The SHDN pin is used to put the LT3505 in V  R =  R OUT 1 2 – 1 shutdown mode. Tie to ground to shut down the LT3505.  0 78V  . Tie to 2.3V or more for normal operation. If the shutdown feature is not used, tie this pin to the VIN pin. SHDN also A good value for R2 is 10.0k. provides a soft-start function; see the Applications Infor-
V
mation section.
C (Pin 8):
The VC pin is used to compensate the LT3505 control loop by tying an external RC network from this
GND (Pin 5):
Tie the GND pin to a local ground plane pin to ground. below the LT3505 and the circuit components. Return the
Exposed Pad (Pin 9):
The Exposed Pad must be soldered feedback divider to this pin. to the PCB and electrically connected to ground. Use a large ground plane and thermal vias to optimize thermal performance. 3505fc 7