LTC4267CDHC datasheet(8/32 Pages) LINEAR

8 / 32 page

LTC4267

4267fc

ITH/RUN (Pin 2/Pin 1): Current Threshold/Run Input. This

pin performs two functions. It serves as the switching

regulator error ampliﬁer compensation point as well as

the run/shutdown control input. Nominal voltage range is

0.7V to 1.9V. Forcing the pin below 0.28V with respect to

PGND causes the controller to shut down.

PGND (Pin 1, 8, 9, 16/Pin 2, 15): Switching Regulator

Negative Supply. This pin is the negative supply rail for the

switching regulator controller and must be tied to POUT.

NGATE (Pin 3/Pin 3): Gate Driver Output. This pin drives

the regulator’s external N-Channel MOSFET and swings

from PGND to PVCC.

PVCC (Pin 4/Pin 4): Switching Regulator Positive Supply.

This pin is the positive supply rail for the switching regula-

tor and must be closely decoupled to PGND.

RCLASS(Pin5/Pin5):ClassSelectInput.Usedtosetthecur-

rent value the PD maintains during classiﬁcation. Connect

a resistor between RCLASS and VPORTN (see Table 2).

VPORTN (Pin 7/Pin 7): Negative Power Input. Tie to the

–48V input port through the input diodes.

POUT (Pin 10/Pin 10): Power Output. Supplies –48V to

the switching regulator PGND pin and any additional PD

loads through an internal power MOSFET that limits input

current. POUT is high impedance until the voltage reaches

the turn-on UVLO threshold. The output is then current

limited. See the Application Information section.

⎯P⎯W⎯R⎯G⎯D (Pin 11/Pin 11):Power Good Output, Open-Drain.

Indicates that the PD MOSFET is on and the switching

regulator can start operation. Low impedance indicates

power is good. ⎯P⎯W⎯R⎯G⎯D is high impedance during detec-

tion, classiﬁcation and in the event of a thermal overload.

⎯P⎯W⎯R⎯G⎯D is referenced to VPORTN.

SIGDISA (Pin 12/Pin 12):Signature Disable Input. SIGDISA

allows the PD to present an invalid signature resistance

and remain inactive. Connecting SIGDISA to VPORTP lowers

the signature resistance to an invalid value and disables

all functions of the LTC4267. If unused, tie SIGDISA to

VPORTN.

VPORTP (Pin 13/Pin 13): Positive Power Input. Tie to the

input port power return through the input diodes.

SENSE (Pin 14/Pin 14): Current Sense. This pin performs

two functions. It monitors the regulator switch current by

reading the voltage across an external sense resistor. It also

injects a current ramp that develops a slope compensation

voltage across an optional external programming resistor.

See the Applications Information section.

VFB (Pin 15/Pin 16): Feedback Input. Receives the feed-

back voltage from the external resistor divider across the

output.

NC (Pin 6/Pin 6, 8, 9): No Internal Connection.

Backside Connection (DHC Only, Pin 17): Exposed Pad.

This exposed pad must be soldered to an electrically isolated

and thermally conductive PC board heat sink.

(GN/DHC)

PI FU CTIO S

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