LT1680ISW datasheet(7/16 Pages) LINER

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LT1680

RUN/SHDN (Pin 11): Precision Referenced Shutdown.

Can be used as logic level input for shutdown control or as

an analog monitor for input supply undervoltage protec-

tion, etc. IC is enabled when RUN/SHDN pin rising edge

exceeds 1.25V. 15mV of hysteresis helps assure stable

mode switching. All internal functions are disabled in

shutdown mode. If this function is not desired, connect

RUN/SHDN to 12VIN (typically through a 100k resistor).

See Applications Information.

PGND (Pin 12): Power Ground. References the output

switch and internal driver control circuits. Connect with

low impedance trace to VIN decoupling capacitor negative

(ground) terminal.

PIN FUNCTIONS

GATE (Pin 13): Driver Output. Connect to gate of external

power FET switch.

12VIN (Pin 14): 12V Power Supply Input. Bypass with at

least 1

µF to PGND.

SYNC (Pin 15): Oscillator Synchronization Pin with

TTL-Level Compatible Input. Input drives internal rising

edge triggered one shot; SYNC signal on/off times should

≥1µs (10% to 90% duty cycle at 100kHz). Does not

contain internal pull-up. Connect to SGND if not used.

5VREF (Pin 16): 5V Reference Output. Allows connection

of external loads up to 10mA DC. Reference is not available

during shutdown. Typically bypassed with at least 1

µF

capacitor to SGND.

REFERENCE

ONE SHOT

–

1.25V

UVLO

CIRCUIT

5VREF

SYNC

GATE

SENSE +

SENSE –

IAVG

VIN

VOUT

RSENSE

12VIN

PGND

SGND

OSC

RCT

CCT

SL/ADJ

VREF

VFB

–

IC1

–

2.5V

1680 BD

–

0.5

µA

CURRENT

SENSE

AMPLIFIER

1.25V

CIRCUIT

ENABLE

RUN/SHDN

RUN SHDN

µA

SOFT START

12V

–

×15

VOUT

BLOCK DIAGRAM

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