LTC1871X datasheet(4/32 Pages) LINER

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LTC1871X

1871xf

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ELECTRICAL CHARACTERISTICS

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: The LTC1871X is guaranteed over the full –40°C to 175°C

operating junction temperature range. High junction temperatures degrade

operating lifetimes. Operating lifetime is derated at junction temperatures

greater than 125°C.

Note 3: TJ is calculated from the ambient temperature TA and power

dissipation PD according to the following formula:

TJ = TA + (PD • 120°C/W)

Note 4: The dynamic input supply current is higher due to power MOSFET

gate charging (QG • fOSC). See Applications Information.

Note 5: The LTC1871X is tested in a feedback loop which servos VFB to

the reference voltage with the ITH pin forced to the midpoint of its voltage

range (0.3V ≤ VITH ≤ 1.2V, midpoint = 0.75V).

Note 6: In a synchronized application, the internal slope compensation

gain is increased by 25%. Synchronizing to a significantly higher ratio will

reduce the effective amount of slope compensation, which could result in

subharmonic oscillation for duty cycles greater than 50%.

Note 7: Rise and fall times are measured at 10% and 90% levels.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

fSYNC/fOSC

Recommended Maximum Synchronized

Frequency Ratio

fOSC = 300kHz (Note 6)

1.25

1.30

fOSC = 300kHz (Note 6), (Note 2)

1.25

1.30

tSYNC(MIN)

MODE/SYNC Minimum Input Pulse Width VSYNC = 0V to 5V

tSYNC(MAX)

MODE/SYNC Maximum Input Pulse Width VSYNC = 0V to 5V

0.8/fOSC

VIL(MODE)

Low Level MODE/SYNC Input Voltage

0.3

(Note 2)

0.3

VIH(MODE)

High Level MODE/SYNC Input Voltage

1.2

(Note 2)

1.2

RMODE/SYNC

MODE/SYNC Input Pull-Down Resistance

kΩ

VFREQ

Nominal FREQ Pin Voltage

0.62

Low Dropout Regulator

VINTVCC

INTVCC Regulator Output Voltage

VIN = 7.5V

5.0

5.2

5.4

∆VINTVCC

∆VIN1

INTVCC Regulator Line Regulation

7.5V ≤ VIN ≤ 15V

∆VINTVCC

∆VIN2

INTVCC Regulator Line Regulation

15V ≤ VIN ≤ 30V

200

VLDO(LOAD)

INTVCC Load Regulation

0 ≤ IINTVCC ≤ 20mA, VIN = 7.5V

–2

–0.2

VDROPOUT

INTVCC Regulator Dropout Voltage

VIN = 5V, INTVCC Load = 20mA

280

IINTVCC

Bootstrap Mode INTVCC Supply Current in

Shutdown

RUN = 0V, SENSE = 5V

μA

GATE Driver

GATE Driver Output Rise Time

CL = 3300pF (Note 7)

100

GATE Driver Output Fall Time

CL = 3300pF (Note 7)

100

The l denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VINTVCC = 5V, VRUN = 1.5V, RFREQ = 80k,

VMODE/SYNC = 0V, unless otherwise speciﬁed.

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