Datasheet LTC3630A (Analog Devices) - 7

LTC3630A
pin FuncTions SW (Pin 1):
Switch Node Connection to Inductor. This
SS (Pin 10):
Soft-Start Control Input. A capacitor to pin connects to the drains of the internal power MOSFET ground at this pin sets the output voltage ramp time. A switches. 50µA current initially charges the soft-start capacitor until
NC (Pins 2, 4, 13, 15 DHC Package Only)
: No Internal switching begins, at which time the current is reduced to Connection. Leave these pins open. its nominal value of 5µA. The output voltage ramp time from zero to its regulated value is 1ms for every 16.5nF
VIN (Pin 3):
Main Input Supply Pin. A ceramic bypass of capacitance from SS to GND. If left floating, the ramp capacitor should be tied between this pin and GND. time defaults to an internal 0.8ms soft-start.
RUN (Pin 5):
Run Control Input. A voltage on this pin
ISET (Pin 11):
Peak Current Set Input and Voltage Output above 1.21V enables normal operation. Forcing this pin Ripple Filter. A resistor from this pin to ground sets the below 0.7V shuts down the LTC3630A, reducing quiescent peak current comparator threshold. Leave floating for the current to approximately 5µA. Optionally, connect to the maximum peak current (1.2A typical) or short to ground input supply through a resistor divider to set the under- for minimum peak current (0.12A typical). The maximum voltage lockout. An internal 2M resistor and 2µA current output current is one-half the peak current. The 5µA current source pulls this pin up to an internal 5V reference. See that is sourced out of this pin when switching, is reduced Applications Information. to 1µA in sleep. Optionally, a capacitor can be placed from
V
this pin to GND to trade off efficiency for light load output
PRG2, VPRG1 (Pins 6, 7):
Output Voltage Selection. Short both pins to ground for an external resistive divider pro- voltage ripple. See Applications Information. grammable output voltage. Short VPRG1 to SS and short
FBO (Pin 12):
Feedback Comparator Output. Connect VPRG2 to ground for a 5V output voltage. Short VPRG1 to to the VFB pins of additional LTC3630As to combine the ground and short VPRG2 to SS for a 3.3V output voltage. output current. The typical pull-up current is 20µA. The Short both pins to SS for a 1.8V output voltage. typical pull- down impedance is 70Ω. See Applications
GND (Pins 8, 14, 16, Exposed Pad Pin 17):
Ground. The Information. exposed backside pad must be soldered to the PCB ground plane for optimal thermal performance.
VFB (Pin 9):
Output Voltage Feedback. When configured for an adjustable output voltage, connect to an external resistive divider to divide the output voltage down for comparison to the 0.8V reference. For the fixed output configuration, directly connect this pin to the output supply. 3630afc For more information www.linear.com/LTC3630A 7 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts