Datasheet LTC1701, LTC1701B (Analog Devices) - 4

LTC1701/LTC1701B
U U U PI FU CTIO S SW (Pin 1):
The Switch Node Connection to the Inductor.
ITH/RUN (Pin 4):
Combination of Error Amplifier Compen- This pin swings from VIN to a Schottky diode (external) sation Point and Run Control Input. The current compara- voltage drop below ground. The cathode of the Schottky tor threshold increases with this control voltage. Nominal diode must be closely connected to this pin. voltage range for this pin is 1.25V to 2.25V. Forcing this pin below 0.8V causes the device to be shut down. In
GND (Pin 2):
Ground Pin. Connect to the (–) terminal of shutdown all functions are disabled. COUT, the Schottky diode and (–) terminal of CIN.
V V IN (Pin 5):
Main Supply Pin and the (+) Input to the
FB (Pin 3):
Receives the feedback voltage from the Current Comparator. Must be closely decoupled to ground. external resistive divider across the output. Nominal volt- age for this pin is 1.25V.
Pin Limit Table NOMINAL (V) ABSOLUTE MAX (V) PIN NAME DESCRIPTION MIN TYP MAX MIN MAX
1 SW Switch Node – 0.3 VIN VIN – 8.5 VIN + 0.3 2 GND Ground Pin 0 3 VFB Output Feedback Pin 0 1.25 1.35 – 0.3 3 4 ITH/RUN Error Amplifier Compensation and RUN Pin 0 2.25 – 0.3 3 5 VIN Main Power Supply 2.5 5.5 – 0.3 6
W BLOCK DIAGRA
V V IN IN VIN 1.25V V BANDGAP REF 50µA (1.25V) REFERENCE + VREF + CURRENT ITH/REF + SENSE CLAMP CURRENT AMP – – COMP 1.5V + – ITH I SHDN COMP VREF TH/RUN – VREF + (LTC1701 only) (1.25V TO 2.25V) ERROR AMP VFB – SW + OFF-TIMER OVER GATE AND GATE VOLTAGE DRIVER CONTROL LOGIC COMP 1.4V – PULSE GND STRETCHER VFB < 0.6V 1701 BD 4