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LTC1871

ELECTRICAL CHARACTERISTICS

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

of the device may be impaired.

Note 2: The LTC1871E is guaranteed to meet performance specifications

from 0

°C to 70°C. Specifications over the –40°C to 85°C operating

temperature range are assured by design, characterization and correlation

with statistical process controls.

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 LTC1871 is tested in a feedback loop that servos VFB to the

reference voltage with the ITH pin forced to a voltage between 0V and 1.4V

(the no load to full load operating voltage range for the ITH pin is 0.3V to

1.23V).

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.

The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.

VIN = VINTVCC = 5V, VRUN = 1.5V, RFREQ = 80k, VMODE/SYNC = 0V, unless otherwise specified.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Oscillator

fOSC

Oscillator Frequency

RFREQ = 80k

250

300

350

kHz

Oscillator Frequency Range

1000

kHz

DMAX

Maximum Duty Cycle

fSYNC/fOSC

Recommended Maximum Synchronized

fOSC = 300kHz (Note 6)

1.25

1.30

Frequency Ratio

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

VIH(MODE)

High Level MODE/SYNC Input Voltage

1.2

RMODE/SYNC MODE/SYNC Input Pull-Down Resistance

Ω

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

INTVCC Regulator Line Regulation

7.5V

≤ VIN ≤ 15V

∆VIN1

∆VINTVCC

INTVCC Regulator Line Regulation

15V

≤ VIN ≤ 30V

200

∆VIN2

VLDO(LOAD)

INTVCC Load Regulation

≤ IINTVCC ≤ 20mA, VIN = 7.5V

– 2

– 0.2

VDROPOUT

INTVCC Regulator Dropout Voltage

VIN = 5V, INTVCC Load = 20mA

280

IINTVCC

Bootstrap Mode INTVCC Supply

RUN = 0V, SENSE = 5V

µA

Current in Shutdown

GATE Driver

GATE Driver Output Rise Time

CL = 3300pF (Note 7)

100

GATE Driver Output Fall Time

CL = 3300pF (Note 7)

100

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