Datasheet LT3503 (Analog Devices) - 6

LT3503
U U U PI FU CTIO S FB (Pin 1):
The LT3503 regulates its feedback pin to
VIN (Pin 5):
The VIN pin supplies current to the LT3503’s 780mV. Connect the feedback resistor divider tap to this internal regulator and to the internal power switch. This pin. Set the output voltage according to: pin must be locally bypassed.
SHDN (Pin 6):
The SHDN pin is used to put the LT3503 in V ⎞ R = ⎛ R OUT 1 2 – 1 ⎝⎜ shutdown mode. Tie to ground to shut down the LT3503. 0 78V ⎠⎟ . Tie to 2.3V or more for normal operation. If the shutdown A good value for R2 is 10.0k. feature is not used, tie this pin to the VIN pin. SHDN also provides a soft-start function; see the Applications Infor-
GND (Pin 2):
Tie the GND pin to a local ground plane below mation section. the LT3503 and the circuit components. Return the feed- back divider to this pin.
Exposed Pad (Pin 7):
The Exposed Pad must be soldered to the PCB and electrically connected to ground. Use a
BOOST (Pin 3):
The BOOST pin is used to provide a drive large ground plane and thermal vias to optimize thermal voltage, higher than the input voltage, to the internal performance. bipolar NPN power switch.
SW (Pin 4):
The SW pin is the output of the internal power switch. Connect this pin to the inductor, catch diode and boost capacitor.
W BLOCK DIAGRA
VIN V 5 IN C2 INT REG AND UVLO D2 ON OFF Σ BOOST 3 SLOPE R R3 COMP Q SHDN 6 C3 S Q DRIVER Q1 C4 L1 OSC SW 4 VOUT C1 D1 FREQUENCY FOLDBACK VC gm 780mV GND FB 2 1 R2 R1 3503 BD 3503f 6