LTC3774 查看數據表（PDF） - Linear Technology

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LTC3774

Dual, Multiphase Current Mode Synchronous Controller

Linear Technology 

LTC3774

PIN FUNCTIONS

PGOOD1, PGOOD2 (Pin 15, Pin 14): Power Good Indica-

tor Outputs. Open drain outputs that pull to ground when

output voltage is not in regulation.

VOSNS1–, VOSNS2– (Pin 26, Pin 3): Remote Sense Differ-

ential Amplifier Inverting inputs. Connect to sense ground

at the output load.

SNSA1+, SNSA2+ (Pin 16, Pin 13): AC Current Sense

Comparator (+) Inputs. This input senses the signal from

the output inductor’s DCR with a filter bandwidth of five

times larger than the inductor’s L/DCR value.

ITH1, ITH2 (Pin 27, Pin 2): Current Control Thresholds

and Error Amplifier Compensation Points. The current

comparator’s threshold increases with the ITH control

voltage.

SNS1–, SNS2– (Pin 17, Pin 12): Negative current Sense

Inputs. The negative input of the current comparator is

normally connected to the output.

SNSD1+, SNSD2+ (Pin 18, Pin 11): DC Current Sense

Comparator (+) Inputs. This input senses the signal from

the output inductor’s DCR with a filter bandwidth equal to

the inductor’s L/DCR value.

RUN1, RUN2 (Pin 20, Pin 9): Run Control Inputs. A volt-

age above 1.22V turns on the IC. There is a 1µA pull-up

current on this pin. Once the RUN pin rises above the

1.22V threshold the pull-up increases to 5µA.

PMW1, PWM2 (Pin 21, Pin 8): (Top) Gate Signal Outputs.

This signal goes to the PWM or top gate input of the ex-

ternal gate driver or integrated driver MOSFET or Power

Block. This is a three-state compatible output.

PWMEN1, PWMEN2 (Pin 22, Pin 7): Enable pins for non-

three-state compatible drivers. This pin has an internal

open-drain pull-up to INTVCC. An external resistor to GND

is required. This pin is low when the corresponding PWM

pin is high impedance.

HIZB1, HIZB2 (Pin 23, Pin 6): Phase Shedding Input Pins.

When this pin is low, the corresponding PWM pin goes

high impedance and PWMEN goes low. Tie to INTVCC or

VIN to disable this function.

TK/SS1, TK/SS2 (Pin 24, Pin 5): Output Voltage Tracking

and Soft-Start Inputs. The voltage ramp rate at this pin

sets the voltage ramp rate of the output. A capacitor to

ground accomplishes soft-start. This pin has a 1.25µA

pull-up current.

VOSNS1+, VOSNS2+ (Pin 25, Pin 4): Remote Sense Differ-

ential Amplifier Non-inverting Inputs. Connect to Feedback

divider center tap with the divider across the output load.

The remote sense differential amplifier’s output is internally

connected to the error amplifier inverting input.

ITEMP1, ITEMP2 (Pin 28, Pin 1): Input of the temperature

sensing comparators. Connect this pin to an external NTC

resistor placed near the inductors. Floating this pin disables

the DCR temperature compensation function.

ILIM1, ILIM2 (Pin 29, Pin 36): Current Comparator Sense

Voltage Limit Selection pins.

PHSMD (Pin 30): Phase Mode Pin. This pin selects CH1-

CH2 and CH1-CLKOUT phase relationships.

FREQ (Pin 31): Frequency Set/Select Pin. A resistor

between this pin and GND sets the switching frequency.

This pin sources 20uA.

MODE/PLLIN (Pin 32): Dual Function Pin. Tying this pin

to GND, INTVCC or floating it enables forced continuous

mode, pulse-skipping mode or Burst Mode operation re-

spectively. Applying a clock signal to this pin causes the

internal PLL to synchronize the internal oscillator to the

clock signal and forces forced continuous mode. The PLL

compensation network is integrated on to the IC.

CLKOUT (Pin 33): Clock Output Pin. This pin is used to

synchronize other LTC3774s.

INTVCC (Pin 34): Internal 5.5V Regulator Output. The con-

trol circuits are powered from this voltage. Decouple this

pin to GND with a minimum of 4.7µF low ESR tantalum

or ceramic capacitor.

VIN (Pin 35): Main Input Supply. Decouple this pin to GND

with a capacitor (0.1µF to 1µF)

GND (Pins 19, 10, Exposed Pad Pin 37): Ground. All

small-signal components and compensation components

should be connected here. The exposed pad must be

soldered to the PCB ground for electrical connection and

rated thermal performance.

3774f

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For more information www.linear.com/LTC3774

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