LTC4258 datasheet(5/42 Pages) LINER

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LTC4278

4278fc

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: Pins with 100V absolute maximum guaranteed for T ≥ 0°C,

otherwise 90V.

Note 3: Active high PWRGD internal clamp self-regulates to 14V with

respect to VNEG.

Note 4: All voltages are with respect to VPORTN pin unless otherwise noted.

Note 5: Input voltage specifications are defined with respect to LTC4278

pins and meet IEEE 802.3af/at specifications when the input diode bridge

is included.

Note 6: Signature resistance is measured via the ∆V/∆I method with the

minimum ∆V of 1V. The LTC4278 signature resistance accounts for the

additional series resistance in the input diode bridge.

Note 7: An invalid signature after the 1st classification event is mandated

by the IEEE802.3at standard. See the Applications Information section.

Note 8: Class accuracy is with respect to the ideal current defined as

1.237/RCLASS and does not include variations in RCLASS resistance.

Note 9: This parameter is assured by design and wafer level testing.

Note 10: VCC = 14V; PG, SG Open; VCMP = 1.4V, VSENSE– = 0V, RCMP = 1k,

RtON = 90k, RPGDLY = 27.4k, RENDLY = 90k, unless otherwise specified. All

voltages are with respect to GND.

Note 11: Supply current does not include gate charge current to the

MOSFETs. See the Applications Information section.

Note 12: Component value range guaranteed by design.

ELECTRICAL CHARACTERISTICS The

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Load Compensation

Load Compensation to VSENSE Offset

Voltage

VRCMP with VSENSE+ = 0V

0.8

Feedback Pin Load Compensation Current

VSENSE+ = 20mV, VFB = 1.230V

µA

UVLO Function

UVLO Pin Threshold (VUVLO)

1.215

1.240

1.265

UVLO Pin Bias Current

VUVLO = 1.2V

VUVLO = 1.3V

–0.25

–4.50

0.1

–3.4

0.25

–2.50

µA

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