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LT1945

1945f

ABSOLUTE

AXI U

RATI GS

PACKAGE/ORDER I FOR ATIO

(Note 1)

VIN, SHDN1, SHDN2 Voltage ................................... 15V

SW1, SW2 Voltage .................................................. 36V

NFB1 Voltage ........................................................... –3V

FB2 Voltage ...............................................................VIN

Current into NFB1 Pin ........................................... –1mA

Current into FB2 Pin .............................................. 1mA

Junction Temperature ........................................... 125

°C

Operating Temperature Range (Note 2) .. – 40

°C to 85°C

Storage Temperature Range ................. – 65

°C to 150°C

Lead Temperature (Soldering, 10 sec).................. 300

°C

ORDER PART

NUMBER

LT1945EMS

MS PART MARKING

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

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Minimum Input Voltage

1.2

Quiescent Current, (per Converter)

Not Switching

µA

VSHDN = 0V

µA

NFB1 Comparator Trip Point

–1.205

–1.23

–1.255

FB2 Comparator Trip Point

1.205

1.23

1.255

FB Comparator Hysteresis

8mV

NFB1, FB2 Voltage Line Regulation

1.2V < VIN < 12V

0.05

0.1

%/V

NFB1 Pin Bias Current (Note 3)

VNFB1 = –1.23V

1.3

2.9

µA

FB2 Pin Bias Current (Note 4)

VFB2 = 1.23V

Switch Off Time, Switcher 1 (Note 5)

400

Switch Off Time, Switcher 2 (Note 5)

VFB2 > 1V

400

VFB2 < 0.6V

1.5

µs

Switch VCESAT

ISW = 300mA

250

350

Switch Current Limit

250

350

400

SHDN Pin Current

VSHDN = 1.2V

µA

VSHDN = 5V

µA

SHDN Input Voltage High

0.9

SHDN Input Voltage Low

0.25

Switch Leakage Current

Switch Off, VSW = 5V

0.01

µA

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

of a device may be impaired.

Note 2: The LT1945 is guaranteed to meet performance specifications

from 0

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

TJMAX = 125°C, θJA = 160°C/W

temperature range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VSHDN = 1.2V unless otherwise noted.

LTTS

Consult LTC Marketing for parts specified with wider operating temperature ranges.

NFB1

SHDN1

GND

SHDN2

FB2

SW1

PGND

VIN

PGND

SW2

TOP VIEW

MS PACKAGE

10-LEAD PLASTIC MSOP

temperature range are assured by design, characterization and correlation

with statistical process controls.

Note 3: Bias current flows out of the NFB1 pin.

Note 4: Bias current flows into the FB2 pin.

Note 5: See Figure 1 for Switcher 1 and Switcher 2 locations.

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