LTC4258 datasheet(4/28 Pages) LINER

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LTC4258

4258p

ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. AGND = DGND = 0V, VDD = 3.3V, VEE = –48V unless otherwise noted

(Note 5).

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

tSTART

Maximum Current Limit Duration During

tSTART1 = 0, tSTART0 = 0 (Figure 3)

Port Start-Up

tSTART1 = 0, tSTART0 = 1

tSTART1 = 1, tSTART0 = 0

100

120

140

tSTART1 = 1, tSTART0 = 1

200

240

280

tICUT

Maximum Current Limit Duration After

tICUT1 = 0, tICUT0 = 0 (Figure 3)

Port Start-Up

tICUT1 = 0, tICUT0 = 1

tICUT1 = 1, tICUT0 = 0

100

120

140

tICUT1 = 1, tICUT0 = 1

200

240

280

DCCLMAX

Maximum Current Limit Duty Cycle

Reg16h = 00h

5.8

6.3

6.7

tDIS

Disconnect Delay

tDIS1 = 0, tDIS0 = 0 (Figure 4)

300

360

400

tDIS1 = 0, tDIS0 = 1

100

tDIS1 = 1, tDIS0 = 0

150

180

200

tDIS1 = 1, tDIS0 = 1

600

720

800

tVMIN

DC Disconnect Minimum Pulse

VSENSEn – VEE > 5mV, VOUTn = –48V (Figure 4)

0.02

Width Sensitivity

(Note 8)

I2C Timing

fSCLK

Clock Frequency

(Note 8)

400

kHz

Bus Free Time

Figure 5 (Notes 8, 9)

1.3

µs

Start Hold Time

Figure 5 (Notes 8, 9)

600

SCL Low Time

Figure 5 (Notes 8, 9)

1.3

µs

SCL High Time

Figure 5 (Notes 8, 9)

600

Data Hold Time

Figure 5 (Notes 8, 9)

150

Data Set-Up Time

Figure 5 (Notes 8, 9)

200

Start Set-Up Time

Figure 5 (Notes 8, 9)

600

Stop Set-Up Time

Figure 5 (Notes 8, 9)

600

SCL, SDAIN Rise Time

Figure 5 (Notes 8, 9)

300

SCL, SDAIN Fall Time

Figure 5 (Notes 8, 9)

150

tFLTINT

Fault Present to INT Pin Low

(Notes 8, 9, 10)

150

tSTOPINT

Stop Condition to INT Pin Low

(Notes 8, 9, 10)

200

tARAINT

ARA to INT Pin High Time

(Notes 8, 9)

300

Note 6: The LTC4258 is designed to maintain a port voltage of –46.6V to

–57V and the VEE supply voltage range accounts for the drop across the

diode, MOSFET and sense resistor.

Note 7: The LTC4258 implements overload current detection per IEEE

802.3af. The minimum overload current (ICUT) is dependent on port

voltage; ICUT_MIN = 15.4W/VPORT_MIN. An IEEE compliant system using the

LTC4258 should maintain port voltage above –46.6V.

Note 8: Guaranteed by design, not subject to test.

Note 9: Values measured at VILD and VIHD.

Note 10: If fault occurs during an I2C transaction, the INT pin will not be

pulled down until a stop condition is present on the I2C bus.

Note 1: Absolute Maximum Ratings are those values beyond which the life

of the device may be impaired.

Note 2: DGND and AGND should be tied together in normal operation.

Note 3: An internal clamp limits the GATE pins to a minimum of 12V above

VEE. Driving this pin beyond the clamp may damage the part.

Note 4: This IC includes overtemperature protection that is intended to

protect the device during momentary overload conditions. Junction

temperature will exceed 125

°C when overtemperature protection is active.

Continuous operation above the specified maximum operating junction

temperature may impair device reliability.

Note 5: All currents into device pins are positive; all currents out of device

pins are negative. All voltages are referenced to ground (AGND and DGND)

unless otherwise specified.

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