LTC7150S datasheet(8/22 Pages) LINER

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LTC7150S

7150sfa

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PIN FUNCTIONS

PHMODE (Pin A1): Control Input to Phase Selector.

Determines the phase relationship between internal

oscillator and CLKOUT. Tie it to INTVCC for 2-phase

operation, tie it to SGND for 3-phase operation, and tie it

to INTVCC/2 (or float the pin) for 4-phase operation.

PGOOD (Pin A2): Output Power Good with Open-Drain

Logic. PGOOD is pulled to ground when the voltage of the

FB pin is not within ±7.5% of the internal 0.6V reference.

RT (Pin A3): Switching Frequency Programming Pin.

Connect an external resistor (between 405k to 54k) from

this pin to GND to program the frequency from 400kHz

to 3MHz.

ITH (Pin A4): Error Amplifier Output and Switching

Regulator Compensation Point. The current comparator’s

tripthresholdislinearlyproportionaltothisvoltage,whose

normal range is from 0.3V to 1.8V.

FB (Pin A5): Feedback Input to the Error Amplifier of the

Step-Down Regulator. Connect resistor divider tap to this

pin. The output voltage can be adjusted from 0.6V to VIN

by: VOUT = 0.6V • [1 + (R1/R2)].

VOUT– (Pin A6): Negative Return of Output Rail. Connect

thispindirectlytothebottomoftheremoteoutputcapacitor

near the load in order to minimize error incurred by voltage

drop across the metal trace of the board.

CLKOUT (Pin B1): Output Clock Signal for PolyPhase

Operation. The phase of CLKOUT with respect to CLKIN

is determined by the state of the PHMODE pin. CLKOUT’s

peak-to-peak amplitude is INTVCC to GND.

RUN(PinB2):LogicControlledRUNInput.Donotleavethis

pin floating. Logic High activates the step-down regulator.

MODE/SYNC (Pin B3): Discontinuous Mode Select

and Oscillator Synchronization Pin. Tie MODE/SYNC

to GND for discontinuous mode of operation. Floating

MODE/SYNC or tying it to a voltage above 1V will select

forcedcontinuousmode.Furthermore,connectingMODE/

SYNC to an external clock will synchronize the system

clock to the external clock and puts the part in forced

continuous mode.

TRACK/SS (Pin B4): Output Tracking and Soft-Start Pin.

Allows the user to control the rise time of the output

voltage. Putting a voltage between 0.6V on this pin relative

to VOUT– bypasses the internal reference input to the error

amplifier, instead it servos the FB pin relative to VOUT– to

that voltage. There’s an internal 5µA pull-up current from

INTVCC to this pin, so putting a capacitor from this pin to

VOUT– provides a soft-start function.

SGND (Pin B5): Signal GND.

INTVCC (Pin B6): Internal 3.3V Regulator Output. The

internal power drivers and control circuits are powered

from this voltage. Decouple this pin to power ground with

a minimum of 4.7µF low ESR ceramic capacitor.

SVIN (Pin C1): Signal VIN. Filtered input voltage to the

on-chip 3.3V regulator. Bypass signal into the SVIN pin

with a 0.1µF ceramic capacitor.

PVIN (Pins C2, C5, C6, D1, D2, D5, D6): Power VIN. Input

voltage to the on chip power MOSFETs.

SW (Pins C3, C4, D3, D4, E3, E4, F3, F4, G3, G4): Switch

Node Connection of External Inductor. Voltage swing of

SW is from a diode voltage drop below ground to a diode

voltage above PVIN.

PGND (Pins E1, E2, E5, E6, F1, F2, F5, F6, G1, G2, G5,

G6): Ground for Power and Signal Ground.

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