LT3092

14

3092fb

Demo circuit 1531A’s board layout using multiple inner

performance for the DFN package.

Table 2. DD Package, 8-Lead DFN

COPPER AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

BOARD AREA

25°C/W

25°C/W

28°C/W

32°C/W

*Device is mounted on topside

Table 3. TS8 Package, 8-Lead SOT-23

COPPER AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

BOARD AREA

54°C/W

54°C/W

57°C/W

63°C/W

*Device is mounted on topside

Table 4. ST Package, 3-Lead SOT-223

COPPER AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

BOARD AREA

20°C/W

20°C/W

24°C/W

29°C/W

*Device is mounted on topside

For further information on thermal resistance and using thermal information,

refer to JEDEC standard JESD51, notably JESD51-12.

Calculating Junction Temperature

Example: Given an industrial factory application with an

input voltage of 15V ±10%, an output voltage of 12V ±5%,

an output current of 200mA and a maximum ambient

temperature of 50°C, what would be the maximum junc-

tion temperature for a DFN package?

The total circuit power equals:

The SET pin current is negligible and can be ignored.

Power dissipation under these conditions equals:

Junction temperature equals:

In this example, the junction temperature is below the

maximum rating, ensuring reliable operation.

Protection Features

The LT3092 incorporates several protection features ideal

for battery-powered circuits, among other applications.

In addition to normal circuit protection features such as

current limiting and thermal limiting, the LT3092 protects

itself against reverse-input voltages, reverse-output volt-

ages, and reverse OUT-to-SET pin voltages.

Current limit protection and thermal overload protection

protect the IC against output current overload condi-

tions. For normal operation, do not exceed a junction

temperature of 125°C. The thermal shutdown circuit’s

typical temperature threshold is 165°C and has about

5°C of hysteresis.

The LT3092’s IN pin withstands ±40V voltages with respect

to the SET and OUT pins. Reverse-current flow, if OUT is

greater than IN, is less than 1mA (typically under 100μA),

protecting the LT3092 and sensitive loads.

Clamping diodes and 1k limiting resistors protect the

LT3092’s SET pin relative to the OUT pin voltage. These

protection components typically only carry current under

transient overload conditions. These devices are sized to

handle ±10V differential voltages and ±15mA crosspin

current flow without concern.

APPLICATIONS INFORMATION