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LT1939

1939f

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

SS Sink Current

VFB = 0V, VSS = 2V

300

600

900

μA

SS POR Sink Current (Note 4)

VFB = 0V, VSS = 2V, Cycle SHDN

400

600

800

μA

SS POR Threshold

VFB = 0V

100

150

SS to FB Offset (VSS – VFB)VVC = 1V, VSS = 0.4V

100

120

PG/PG Leakage

VFB = 0.9V/0.7V, VPG/VPG = 25V

0.1

μA

PG/ PG Threshold

VPG = 0.4V

0.685

0.708

0.730

PG/ PG Hysteresis

VPG = 0.4V

PG Sink Current

VPG = 0.4V, VFB = 0.7V

250

500

750

μA

PG Sink Current

VPG = 0.4V, VFB = 0.9V

500

800

1100

μA

RT/SYNC Reference Voltage

VFB1/2 = 0.9V, RRT/SYNC = 15k

0.75

0.850

0.975

Switching Frequency

RRT/SYNC = 90.9k

RRT/SYNC = 15k

450

425

500

2.4

550

625

2.8

kHz

MHz

SYNC Frequency Range

250

2500

kHz

Minimum Switch On Time

VFB = 0.7V, RRT/SYNC = 90.9k

140

Minimum Switch Off Time

VFB = 0.7V, RRT/SYNC = 90.9k

120

Switch Leakage Current

VSW = 0V

μA

Switch Saturation Voltage

ISW = 2A, VBST = 18V, VFB = 0.7V

450

Switch Peak Current

VBST = 18V, VFB = 0.7V

2.3

2.1

2.8

3.5

Boost Current

ISW = 2A, VBST = 18V, VFB = 0.7V

Minimum Boost Voltage (Note 5)

ISW = 2A, VFB = 0.7V

2.2

LFB Voltage

VLDRV = 1.2V

0.784

0.8

0.816

LFB Line/Load Regulation

VVIN = 3V to 25V, VLDRV = 8V

0.776

0.8

0.824

SS to LFB Offset (VSS – VLFB)VVC = 1V, VSS = 0.8V, VLDRV = VLFB

115

140

LFB Bias Current

VLFB = 0.8V, VVC = 1V

115

300

LDRV Dropout

VLDRV = 3V, ILDRV = 5mA

0.8

1.2

1.6

LDRV Maximum Current

VLDRV = 0V

913

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

temperature range, otherwise speciﬁcations are at TJ = 25°C. VVIN = 15V, VRT/SYNC = 2V, unless otherwise speciﬁed.

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.

Note2: The LT1939EDD is guaranteed to meet performance speciﬁcations

from 0°C to 125°C junction temperature. Speciﬁcations over the –40°C

to 125°C operating junction temperature range are assured by design,

characterization and correlation with statistical process controls. The

LT1939IDD is guaranteed over the full –40°C to 125°C operating junction

temperature range.

Note 3: Minimum input voltage is deﬁned as the voltage where internal

bias lines are regulated so that the reference voltage and oscillator remain

constant. Actual minimum input voltage to maintain a regulated output

will depend upon output voltage and load current. See Applications

Information.

Note 4: An internal power-on reset (POR) latch is set on the positive

transition of the SHDN pin through its threshold. The output of the latch

activates a current source on the SS pin which typically sinks 600μA,

discharging the SS capacitor. The latch is reset when the SS pin is driven

below the soft-start POR threshold or the SHDN pin is taken below its

threshold.

Note 5: This is the minimum voltage across the boost capacitor needed to

guarantee full saturation of the internal power switch.

Note 6: This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction

temperature will exceed the maximum operating junction temperature

when overtemperature protection is active. Continuous operation above

the speciﬁed maximum operating junction temperature may impair device

reliability.

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