LTC3704 Datasheet, PDF(6/28 Page) Linear Technology – Wide Input Range, No RSENSE Positive-to-Negative DC/DC Controller

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LTC3704 Datasheet, PDF (6/28 Pages) Linear Technology – Wide Input Range, No RSENSE Positive-to-Negative DC/DC Controller

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LTC3704

PI FU CTIO S

RUN (Pin 1): The RUN pin provides the user with an

accurate means for sensing the input voltage and pro-

gramming the start-up threshold for the converter. The

falling RUN pin threshold is nominally 1.248V and the

comparator has 100mV of hysteresis for noise immunity.

When the RUN pin is below this input threshold, the IC is

shut down and the VIN supply current is kept to a low

value (typ 10ÂµA). The Absolute Maximum Rating for the

voltage on this pin is 7V.

ITH (Pin 2): Error Amplifier Compensation Pin. The cur-

rent comparator input threshold increases with this

control voltage. Nominal voltage range for this pin is 0V

to 1.40V.

NFB (Pin 3): Receives the feedback voltage from the

external resistor divider across the output. Nominal

voltage for this pin in regulation is â1.230V.

FREQ (Pin 4): A resistor from the FREQ pin to ground

programs the operating frequency of the chip. The nomi-

nal voltage at the FREQ pin is 0.62V.

MODE/SYNC (Pin 5): This input controls the operating

mode of the converter and allows for synchronizing the

operating frequency to an external clock. If the MODE/

SYNC pin is connected to ground, Burst Mode operation

is enabled. If the MODE/SYNC pin is connected to INTVCC,

or if an external logic-level synchronization signal is

applied to this input, Burst Mode operation is disabled

and the IC operates in a continuous mode.

GND (Pin 6): Ground Pin.

GATE (Pin 7): Gate Driver Output.

INTVCC (Pin 8): The Internal 5.20V Regulator Output. The

gate driver and control circuits are powered from this

voltage. Decouple this pin locally to the IC ground with a

minimum of 4.7ÂµF low ESR tantalum or ceramic

capacitor.

VIN (Pin 9): Main Supply Pin. Must be closely decoupled

to ground.

SENSE (Pin 10): The Current Sense Input for the Control

Loop. Connect this pin to the drain of the power MOSFET

for VDS sensing and highest efficiency. Alternatively, the

SENSE pin may be connected to a resistor in the source

of the power MOSFET. Internal leading edge blanking is

provided for both sensing methods.

sn3704 3704fs

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