Datasheet LT3470 (Analog Devices) - 7

LT3470
PIN FUNCTIONS (ThinSOT/DD) SHDN (Pin 1/Pin 8):
The SHDN pin is used to put the
BOOST (Pin 6/Pin 3):
The BOOST pin is used to provide LT3470 in shutdown mode. Tie to ground to shut down a drive voltage, which is higher than the input voltage, to the LT3470. Apply 2V or more for normal operation. If the the internal bipolar NPN power switch. shutdown feature is not used, tie this pin to the VIN pin.
BIAS (Pin 7/Pin 2):
The BIAS pin connects to the internal
NC (Pin 2/Pin 7):
This pin can be left floating or connected boost Schottky diode and to the internal regulator. Tie to to VIN. VOUT when VOUT > 2V or to VIN otherwise. When VBIAS >
V
3V the BIAS pin will supply current to the internal regulator.
IN (Pin 3/Pin 6):
The VIN pin supplies current to the LT3470’s internal regulator and to the internal power
FB (Pin 8/Pin 1):
The LT3470 regulates its feedback pin switch. This pin must be locally bypassed. to 1.25V. Connect the feedback resistor divider tap to this
GND (Pin 4/Pin 5):
Tie the GND pin to a local ground plane pin. Set the output voltage according to VOUT = 1.25V below the LT3470 and the circuit components. Return the (1 + R1/R2) or R1 = R2 (VOUT/1.25 – 1). feedback divider to this pin.
Exposed Pad (DD, Pin 9):
Ground. Must be soldered to
SW (Pin 5/Pin 4):
The SW pin is the output of the internal PCB. power switch. Connect this pin to the inductor, catch diode and boost capacitor.
BLOCK DIAGRAM
VIN BIAS VIN C1 + – BOOST 500ns ONE SHOT R Q′ C3 S Q – SW L1 VOUT C2 ENABLE + Burst Mode NC DETECT SHDN VREF 1.25V gm FB GND R2 R1 3470 BD Rev. E For more information www.analog.com 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Related Parts