LT1375CS8 datasheet(4/28 Pages) LINER

4 / 28 page

LT1375/LT1376

Kool M

µ is a registered trademark of Magnetics, Inc.

ELECTRICAL CHARACTERISTICS

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

of a device may be impaired.

Note 2: Gain is measured with a VC swing equal to 200mV above the low

clamp level to 200mV below the upper clamp level.

Note 3: Minimum input voltage is not measured directly, but is guaranteed

by other tests. It is defined as the voltage where internal bias lines are still

regulated so that the reference voltage and oscillator frequency remain

constant. Actual minimum input voltage to maintain a regulated output will

depend on output voltage and load current. See Applications Information.

Note 4: This is the minimum voltage across the boost capacitor needed to

guarantee full saturation of the internal power switch.

Note 5: Boost current is the current flowing into the BOOST pin with the

pin held 5V above input voltage. It flows only during switch-on time.

Note 6: Input supply current is the bias current drawn by the input pin

when the BIAS pin is held at 5V with switching disabled. Output supply

current is the current drawn by the BIAS pin when the bias pin is held at

5V. Total input referred supply current is calculated by summing input

supply current (ISI) with a fraction of output supply current (ISO):

ITOT = ISI + (ISO)(VOUT/VIN)(1.15)

With VIN = 15V, VOUT = 5V, ISI = 0.9mA, ISO = 3.6mA, ITOT = 2.28mA.

For the LT1375, quiescent current is equal to:

ITOT = ISI + ISO(1.15)

because the BIAS pin is internally connected to VIN.

Note 7: Switch-on resistance is calculated by dividing VIN to VSW voltage

by the forced current (1.5A). See Typical Performance Characteristics for

the graph of switch voltage at other currents.

Note 8: Transconductance and voltage gain refer to the internal amplifier

exclusive of the voltage divider. To calculate gain and transconductance

refer to sense pin on fixed voltage parts. Divide values shown by the ratio

VOUT/2.42.

The q denotes specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. TJ = 25°C, VIN = 15V, VC = 1.5V, boost open, switch open,

unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Shutdown Thresholds

VC Open

Device Shutting Down

0.15

0.37

0.60

Device Starting Up

0.25

0.45

0.60

VC Open

LT1375HV/LT1376HV Device Shutting Down

0.15

0.37

0.70

LT1375HV/LT1376HV Device Starting Up

0.25

0.45

0.70

Minimum Synchronizing Amplitude (LT1375 Only)

VIN = 5V

1.5

2.2

Synchronizing Range (LT1375 Only)

580

900

kHz

SYNC Pin Input Resistance

Ω

INDUCTANCE (

µH)

1.0

0.1

0.01

0.001

1.2

0.8

0.4

0.2

0.12

0.08

0.04

0.02

1375/76 G01

TYPE 52

POWDERED IRON

Kool M

µ®

PERMALLOY

µ = 125

VOUT = 5V, VIN = 10V, IOUT = 1A

CORE LOSS IS

INDEPENDENT OF LOAD

CURRENT UNTIL LOAD CURRENT FALLS

LOW ENOUGH FOR CIRCUIT TO GO INTO

DISCONTINUOUS MODE

Inductor Core Loss

TYPICAL PERFORMANCE CHARACTERISTICS

DUTY CYCLE (%)

2.5

2.0

1.5

1.0

0.5

1375/76 G08

100

TYPICAL

GUARANTEED MINIMUM

Switch Peak Current Limit

JUNCTION TEMPERATURE (

°C)

–50

2.44

2.43

2.42

2.41

2.40

100

1375/76 G09

–25

125

2.0

1.5

1.0

0.5

VOLTAGE

CURRENT

Feedback Pin Voltage and Current

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