LTC3716_15 datasheet(8/28 Pages) LINER

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LTC3716

PI FU CTIO S

RUN/SS (Pin 1): Combination of Soft-Start, Run Control

Input and Short-Circuit Detection Timer. A capacitor to

ground at this pin sets the ramp time to full current output.

Forcing this pin below 0.8V causes the IC to shut down all

internal circuitry. All functions are disabled in shutdown.

SENSE1+, SENSE2+ (Pins 2,14): The (+) Input to Each

Differential Current Comparator. The ITH pin voltage and

built-in offsets between SENSE– and SENSE+ pins in

conjunction with RSENSE set the current trip threshold.

SENSE1–, SENSE2– (Pins 3,13): The (–) Input to the

Differential Current Comparators.

EAIN (Pin 4): Input to the error amplifier that compares the

feedback voltage to the internal 0.6V reference voltage.

This pin is normally connected to a resistive divider from

the output of the differential amplifier (DIFFOUT).

PLLFLTR (Pin 5): The phase-locked loop’s lowpass filter

is tied to this pin. Alternatively, this pin can be driven with

an AC or DC voltage source to vary the frequency of the

internal oscillator. Do not apply voltage to this pin prior to

application of VIN.

PLLIN (Pin 6): External Synchronization Input to Phase

Detector. This pin is internally terminated to SGND with

50k

Ω. The phase-locked loop will force the rising top gate

signal of controller 1 to be synchronized with the rising

edge of the PLLIN signal.

FCB (Pin 7): Forced Continuous Control Input. This input

acts on both output stages and can be used to regulate a

secondary winding. Pulling this pin below 0.6V will force

continuous synchronous operation. Do not leave this pin

floating without a decoupling capacitor.

ITH (Pin 8): Error Amplifier Output and Switching Regula-

tor Compensation Point. Both current comparator’s thresh-

olds increase with this control voltage. The normal voltage

range of this pin is from 0V to 2.4V

SGND (Pin 9): Signal Ground. This pin is common to both

controllers. Route separately to the PGND pin.

VDIFFOUT (Pin 10): Output of a Differential Amplifier. This

pin provides true remote output voltage sensing. VDIFFOUT

normally drives an external resistive divider that sets the

output voltage.

VOS–, VOS+ (Pins 11, 12): Inputs to an Operational Ampli-

fier. Internal precision resistors configure it as a differen-

tial amplifier whose output is VDIFFOUT.

ATTENOUT (Pin 15): Voltage Feedback Signal Resistively

Divided According to the VID Programming Code.

ATTENIN (Pin 16): The Input to the VID Controlled Resis-

tive Divider.

VID0–VID4 (Pins 17,18, 19, 20, 21): VID Control Logic

Input Pins.

VBIAS (Pin 22): Supply Pin for the VID Control Circuit.

AMPMD (Pin 23): This Logic Input pin controls the con-

nections of internal precision resistors that configure the

operational amplifier as a unity-gain differential amplifier.

TG2, TG1 (Pins 24, 35): High Current Gate Drives for Top

N-Channel MOSFETS. These are the outputs of floating

drivers with a voltage swing equal to INTVCC superim-

posed on the switch node voltage SW.

SW2, SW1 (Pins 25, 34): Switch Node Connections to

Inductors. Voltage swing at these pins is from a Schottky

diode (external) voltage drop below ground to VIN.

BOOST2, BOOST1 (Pins 26, 33): Bootstrapped Supplies

to the Topside Floating Drivers. External capacitors are con-

nected between the BOOST and SW pins, and Schottky

diodes are connected between the BOOST and INTVCC pins.

BG2, BG1 (Pins 27, 31): High Current Gate Drives for

Bottom N-Channel MOSFETS. Voltage swing at these pins

is from ground to INTVCC.

PGND (Pin 28): Driver Power Ground. Connect to sources

of bottom N-channel MOSFETS and the (–) terminals of CIN.

INTVCC (Pin 29): Output of the Internal 5V Linear Low

Dropout Regulator and the EXTVCC Switch. The driver and

control circuits are powered from this voltage source.

Decouple to power ground with a 1

µF ceramic capacitor

placed directly adjacent to the IC and minimum of 4.7

µF

additional tantalum or other low ESR capacitor.

EXTVCC (Pin 30): External Power Input to an Internal

Switch. This switch closes and supplies INTVCC, bypass-

ing the internal low dropout regulator whenever EXTVCC is

higher than 4.7V. See EXTVCC Connection in the Applica-

tions Information section. Do not exceed 7V on this pin

and ensure VEXTVCC ≤ VINTVCC.

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