Datasheet LTC1622 (Analog Devices) - 4

LTC1622
W U TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load Current for Figure 1 with Burst Mode Load Step Transient Response Load Step Transient Response Operation Defeated Burst Enabled Burst Inhibited
100 VIN = 3.3V 90 VIN = 4.2V 80 70 V 100mV/DIV 100mV/DIV IN = 6V EFFICIENCY (%) V 60 IN = 8.4V 50 VOUT = 2.5V ILOAD = 50mA TO 1.2A ILOAD = 50mA TO 1.2A RSENSE = 0.03Ω VIN = 4.2V VIN = 4.2V 40 1622 G08 1622 G09 1 10 100 1000 LOAD CURRENT (mA) 1622 G07
U U U PIN FUNCTIONS SENSE– (Pin 1):
The Negative Input to the Current Com-
SYNC/MODE (Pin 5):
This pin performs three functions. parator. Greater than 2V on this pin allows Burst Mode operation at low load currents, while grounding or applying a clock
ITH (Pin 2):
Error Amplifier Compensation Point. The signal on this pin defeats Burst Mode operation. An current comparator threshold increases with this control external clock between 625kHz and 750kHz applied to this voltage. Nominal voltage range for this pin is 0V to 1.2V. pin forces the LTC1622 to operate at the external clock
VFB (Pin 3):
Receives the feedback voltage from an exter- frequency. Do not attempt to synchronize below 625kHz. nal resistive divider across the output capacitor. Pin 5 has an internal 1µA pull-up current source.
RUN/SS (Pin 4):
Combination of Soft-Start and Run
GND (Pin 6):
Ground Pin. Control Inputs. A capacitor to ground at this pin sets the
PDRV (PIN 7):
Gate Drive for the External P-Channel ramp time to full output current. The time is approximately MOSFET. This pin swings from 0V to V 0.45s/µF. Forcing this pin below 0.4V causes all circuitry IN. to be shut down.
VIN (Pin 8):
Main Supply Pin. Must be closely decoupled to ground Pin 6. 4