LT1963 datasheet(18/28 Pages) LINER

18 / 28 page

LT3089

3089f

For more information www.linear.com/LT3089

Connecting a resistor from IMON to ground converts the

IMON pin current into a voltage to allow for monitoring by

an ADC. With a 1k resistor, 0mV to 160mV indicates 0A

to 800mA of load current.

Compensating for Cable Drops with IMON

The IMON pin can compensate for resistive drops in wires

or cables between the LT3089 and the load. Breaking the

SET resistor into two pieces adjusts the output voltage as a

function of load current. The ratio of the output wire/cable

impedance to the bottom resistor should be 1:5000. The

sum total of the two SET resistor values determines the

initial output voltage. Figure 11 shows a typical application

and formulas for calculating resistor values.

PC board, copper traces and planes. Surface mount heat

sinks, plated through-holes and solder-filled vias can also

spread the heat generated by power devices.

Junction-to-case thermal resistance is specified from the

IC junction to the bottom of the case directly, or the bot-

tom of the pin most directly in the heat path. This is the

lowest thermal resistance path for heat flow. Only proper

device mounting ensures the best possible thermal flow

from this area of the packages to the heat sinking material.

Note that the exposed pad of the DFN and TSSOP pack-

ages and the tab of the DD-Pak package are electrically

connected to the output (VOUT).

Tables 3 through 5 list thermal resistance as a function

of copper areas on a fixed board size. All measurements

were taken in still air on a 4-layer FR-4 board with 1oz

solid internal planes and 2oz external trace planes with a

total finished board thickness of 1.6mm.

Table 3. DF Package, 12-Lead DFN

COPPER AREA

BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

2500mm2

21°C/W

1000mm2

2500mm2

24°C/W

225mm2

2500mm2

30°C/W

100mm2

2500mm2

35°C/W

*Device is mounted on topside

Table 4. FE Package, 16-Lead TSSOP

COPPER AREA

BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

2500mm2

18°C/W

1000mm2

2500mm2

22°C/W

225mm2

2500mm2

27°C/W

100mm2

2500mm2

32°C/W

*Device is mounted on topside

Table 5. R Package, 7-Lead DD-Pak

COPPER AREA

BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

2500mm2

13°C/W

1000mm2

2500mm2

14°C/W

225mm2

2500mm2

16°C/W

*Device is mounted on topside

APPLICATIONS INFORMATION

Figure 11. Using IMON to Compensate for Cable Drops

Thermal Considerations

The LT3089’s internal power and thermal limiting circuitry

protects itself under overload conditions. For continuous

normal load conditions, do not exceed the 125°C (E- and

I-grades) maximum junction temperature. Carefully

consider all sources of thermal resistance from junction-

to-ambient. This includes (but is not limited to) junction-

to-case, case-to-heat sink interface, heat sink resistance

or circuit board-to-ambient as the application dictates.

Consider all additional, adjacent heat generating sources

in proximity on the PCB.

Surface mount packages provide the necessary heat

sinking by using the heat spreading capabilities of the

LT3089

CIN

1µF

COUT

10µF

3089 F11

OUT

SET

RSET

29.8k

RCOMP = 5000 • RCABLE(TOTAL)

VOUT(LOAD) = 50µA (RSET + RCOMP)

RCABLE2

0.02

RCABLE

0.02

RCOMP

200

IMON

LOAD

LT1963 датащи(PDF) 18 Page - Linear Technology

LT1963 датащи(HTML) 18 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

датащи скачать

ссылки URL