LTC3589 datasheet(12/36 Pages) LINER

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LTC3375

3375fa

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pin FuncTions

FB1 (Pin 1): Buck Regulator 1 Feedback Pin. Receives

feedbackbyaresistordividerconnectedacrosstheoutput.

VIN1 (Pin 2): Buck Regulator 1 Input Supply. Bypass to

GND with a 10µF or larger ceramic capacitor.

SW1 (Pin 3): Buck Regulator 1 Switch Node. External

inductor connects to this pin.

SW2 (Pin 4): Buck Regulator 2 Switch Node. External

inductor connects to this pin.

VIN2(Pin5):BuckRegulator2InputSupply.BypasstoGND

with a 10µF or larger ceramic capacitor. May be driven by

an independent supply or must be shorted to VIN1 when

buck regulator 2 is combined with buck regulator 1 for

higher current.

FB2 (Pin 6): Buck Regulator 2 Feedback Pin. Receives

feedbackbyaresistordividerconnectedacrosstheoutput.

Connecting FB2 to VIN2 combines buck regulator 2 with

buck regulator 1 for higher current. Up to 4 converters

may be combined in this way.

FB3 (Pin 7): Buck Regulator 3 Feedback Pin. Receives

feedbackbyaresistordividerconnectedacrosstheoutput.

Connecting FB3 to VIN3 combines buck regulator 3 with

buck regulator 2 for higher current. Up to 4 converters

may be combined in this way.

VIN3(Pin8):BuckRegulator3InputSupply.BypasstoGND

with a 10µF or larger ceramic capacitor. May be driven by

an independent supply or must be shorted to VIN2 when

buck regulator 3 is combined with buck regulator 2 for

higher current.

SW3 (Pin 9): Buck Regulator 3 Switch Node. External

inductor connects to this pin.

SW4 (Pin 10): Buck Regulator 4 Switch Node. External

inductor connects to this pin.

VIN4 (Pin 11): Buck Regulator 4 Input Supply. Bypass

to GND with a 10µF or larger ceramic capacitor. May be

drivenbyanindependentsupplyormustbeshortedtoVIN3

when buck regulator 4 is combined with buck regulator 3

for higher current.

FB4 (Pin 12): Buck Regulator 4 Feedback Pin. Receives

feedbackbyaresistordividerconnectedacrosstheoutput.

Connecting FB4 to VIN4 combines buck regulator 4 with

buck regulator 3 for higher current. Up to 4 converters

may be combined in this way.

EN4 (Pin 13): Buck Regulator 4 Enable Input. Active high.

EN3 (Pin 14): Buck Regulator 3 Enable Input. Active high.

IRQ(Pin15):InterruptPin(ActiveLow).Open-drainoutput.

Whenanundervoltage,dietemperature,orunmaskederror

condition is detected, this pin is driven LOW.

RST (Pin 16): Reset Pin (Active Low). Open-drain output.

When the regulated output voltage of any unmasked

enabled switching regulator is more than 7.5% below its

programmed level, this pin is driven LOW. Assertion delay

is scaled by the CT capacitor. When all buck regulators are

disabled RST is driven LOW.

CT (Pin 17): Timing Capacitor Pin. A capacitor connected

to GND sets a time constant which is scaled for use by

the ON, KILL, PB, RST and IRQ pins.

SYNC (Pin 18): Oscillator Synchronization Pin. Driving

SYNC with an external clock signal will synchronize all

switcherstotheappliedfrequency.Theslopecompensation

is automatically adapted to the external clock frequency.

The absence of an external clock signal will enable the

frequency programmed by the RT pin. Do not float.

RT (Pin 19): Oscillator Frequency Pin. This pin provides

twomodesofsettingtheswitchingfrequency.Connectinga

resistorfromRTtogroundwillsettheswitchingfrequency

based on the resistor value. If RT is tied to VCC the default

LTC3589 Datasheet(PDF) 12 Page - Linear Technology

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