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LT1619

1619fa

–

ILIM

1619 F02

CURRENT

LIMIT

COMPARATOR

DRIVER

280ns

CURRENT

SENSE

AMP

GATE

DRV

VIN

GND

SENSE

RSENSE

LOAD

LEADING

EDGE

BLANKING

SYNC

RAMP COMP

300kHz

OSCILLATOR

SHUTDOWN

DELAY

REF/BIAS

S/S 1

1.24V

1.8V

VIN

CLK

IDLE

UVLO

–

ERROR

AMPLIFIER

Figure 2. LT1619 Block Diagram

S/S (Pin 1): Shutdown and Synchronization. Shutdown is

active low with a typical threshold voltage of 0.9V. For

normal operation, the S/S pin is tied to VIN. To externally

synchronize the controller, drive the S/S pin with pulses.

FB (Pin 2): The inverting Input of the Error Amplifier.

Connect the resistor divider tap here. Set VOUT according

to VOUT = 1.24(1 + R1/R2). See Figure 1.

VC (Pin 3): Compensation Pin for the Error Amplifier. VC is

the output of the transconductance amplifier. Overall loop

is compensated with an RC network from this pin to the

ground.

GND (Pin 4): Ground. Connect to local ground plane.

SENSE (Pin 5): The Input of the Current Sense Amplifier.

The SENSE pin is connected to the source of the N-channel

MOSFET and to a sense resistor to the ground. The current

limit threshold is internally set at 53mV, giving a maximum

switch current of 53mV/RSENSE.

GATE (Pin 6): The Output of the MOSFET Driver.

DRV (Pin 7): The Pull-Up Supply of the MOSFET Driver. Tie

this pin to VIN (Pin 8) for nonbootstrapped operation or to

the converter output for bootstrapped operation.

VIN (Pin 8): Supply or Battery Input. Must be closely

bypassed to the ground plane.

PI FU CTIO S

BLOCK DIAGRA

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