LTC3867_15 Datasheet, PDF(9/36 Page) Linear Technology – Low IQ, Dual 2-Phase Synchronous Step-Down Controller

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LTC3867_15 Datasheet, PDF (9/36 Pages) Linear Technology – Low IQ, Dual 2-Phase Synchronous Step-Down Controller

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LTC3867

PIN FUNCTIONS

INTVCC (Pin 16): Internal 5.3V Regulator Output and

Bottom MOSFET Driver Supply. The control circuits are

powered from this voltage. Decouple this pin to PGND

with a minimum of 4.7ÂµF low ESR tantalum or ceramic

capacitor.

BG (Pin 17): Bottom Gate Driver Output. This pin drives

the gate(s) of the bottom N-channel MOSFET(s) between

PGND and INTVCC.

PGND (Pin 18): Power Ground Pin. Connect this pin closely

to the source(s) of the bottom N-channel MOSFET(s), the

(â) terminal of CVCC and (â) terminal of CIN.

SW (Pin 19): Switch Node Connection to the Inductor.

Voltage swing at this pin is from a Schottky diode (external)

voltage drop below ground to VIN.

TG (Pin 20): Top Gate Driver Output. This is the output of

the floating driver with a voltage swing equal to INTVCC

superimposed on the SW voltage.

BOOST (Pin 21): Boosted Floating Driver Supply. The (+)

terminal of the bootstrap capacitor connects to this pin.

This pin swings from a diode drop below INTVCC up to

VIN + INTVCC.

PGOOD (Pin 22): Power Good Indicator Output. Open-

drain output that pulls to ground when output voltage is

not in regulation.

MODE/PLLIN (Pin 23): This is a dual function pin. Tying

this pin to SGND, INTVCC or floating it enables forced

continuous mode, pulse-skipping mode or Burst Mode

operation respectively. Applying a clock signal to this pin

causes the internal PLL to synchronize the internal oscilla-

tor to the clock signal and forces forced continuous mode.

The PLL compensation network is integrated on to the IC.

FREQ (Pin 24): Frequency Set/Select Pin. A resistor be-

tween this pin and SGND sets the switching frequency.

This pin sources 20ÂµA.

SGND (Exposed Pad Pin 25): Signal Ground. The exposed

pad must be soldered to the PCB ground for electrical con-

nection and rated thermal performance. All small-signal

components and compensation components should be

connected here. Connect to PGND at one point, close to

the IC.

3867f

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