LTC1622 データシートの表示（PDF） - Linear Technology

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LTC1622

Low Input Voltage Current Mode Step-Down DC/DC Controller

Linear Technology 

LTC1622

TYPICAL PERFORMANCE CHARACTERISTICS

Efficiency vs Load Current for

Figure 1 with Burst Mode

Operation Defeated

100

VIN = 3.3V

90

VIN = 4.2V

80

70

VIN = 6V

60

VIN = 8.4V

50

40

1

VOUT = 2.5V

RSENSE = 0.03Ω

10

100

LOAD CURRENT (mA)

1000

1622 G07

Load Step Transient Response

Burst Enabled

ILOAD = 50mA TO 1.2A

VIN = 4.2V

1622 G08

Load Step Transient Response

Burst Inhibited

ILOAD = 50mA TO 1.2A

VIN = 4.2V

1622 G09

PIN FUNCTIONS

SENSE– (Pin 1): The Negative Input to the Current Com-

parator.

ITH (Pin 2): Error Amplifier Compensation Point. The

current comparator threshold increases with this control

voltage. Nominal voltage range for this pin is 0V to 1.2V.

VFB (Pin 3): Receives the feedback voltage from an exter-

nal resistive divider across the output capacitor.

RUN/SS (Pin 4): Combination of Soft-Start and Run

Control Inputs. A capacitor to ground at this pin sets the

ramp time to full output current. The time is approximately

0.45s/µF. Forcing this pin below 0.4V causes all circuitry

to be shut down.

SYNC/MODE (Pin 5): This pin performs three functions.

Greater than 2V on this pin allows Burst Mode operation

at low load currents, while grounding or applying a clock

signal on this pin defeats Burst Mode operation. An

external clock between 625kHz and 750kHz applied to this

pin forces the LTC1622 to operate at the external clock

frequency. Do not attempt to synchronize below 625kHz.

Pin 5 has an internal 1µA pull-up current source.

GND (Pin 6): Ground Pin.

PDRV (PIN 7): Gate Drive for the External P-Channel

MOSFET. This pin swings from 0V to VIN.

VIN (Pin 8): Main Supply Pin. Must be closely decoupled

to ground Pin 6.

4

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