Datasheet

LT3024
16
3024fa
APPLICATIONS INFORMATION
and its copper traces. Copper board stiffeners and plated
through-holes can also be used to spread the heat gener-
ated by power devices.
The following tables list thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on 3/32" FR-4 board with one ounce
copper.
Table 1. FE Package, 16-Lead TSSOP
COPPER AREA
BOARD AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)TOPSIDE* BACKSIDE
2500mm
2
2500mm
2
2500mm
2
38°C/W
1000mm
2
2500mm
2
2500mm
2
43°C/W
225mm
2
2500mm
2
2500mm
2
48°C/W
100mm
2
2500mm
2
2500mm
2
60°C/W
*Device is mounted on topside.
Table 2. UE Package, 12-Lead DFN
COPPER AREA
BOARD AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)TOPSIDE* BACKSIDE
2500mm
2
2500mm
2
2500mm
2
40°C/W
1000mm
2
2500mm
2
2500mm
2
45°C/W
225mm
2
2500mm
2
2500mm
2
50°C/W
100mm
2
2500mm
2
2500mm
2
62°C/W
*Device is mounted on topside.
The thermal resistance junction-to-case (θ
JC
), measured
at the Exposed Pad on the back of the die is 10°C/W for
the DFN package and 8°C/W for the TSSOP package.
Calculating Junction Temperature
Example: Given Output 1 set for an output voltage of
3.3V, Output 2 set for an output voltage of 2.5V, an input
voltage range of 3.8V to 5V, an output current range of
0mA to 500mA for Output 1, an output current range of
0mA to 100mA for Output 2 and a maximum ambient
temperature of 50°C, what will the maximum junction
temperature be?
The power dissipated by each output will be equal to:
I
OUT(MAX)
(V
IN(MAX)
– V
OUT
) + I
GND
(V
IN(MAX)
)
Where for Output 1:
I
OUT(MAX)
= 500mA
V
IN(MAX)
= 5V
I
GND
at (I
OUT
= 500mA, V
IN
= 5V) = 9mA
For Output 2:
I
OUT(MAX)
= 100mA
V
IN(MAX)
= 5V
I
GND
at (I
OUT
= 100mA, V
IN
= 5V) = 2mA
So for Output 1:
P = 500mA (5V – 3.3V) + 9mA (5V) = 0.90W
For Output 2:
P = 100mA (5V – 2.5V) + 2mA (5V) = 0.26W
The thermal resistance will be in the range of 35°C/W to
55°C/W depending on the copper area. So the junction
temperature rise above ambient will be approximately
equal to:
(0.90W + 0.26W) 50°C/W = 57.8°C
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
T
JMAX
= 50°C + 57.8°C = 107.8°C
Protection Features
The LT3024 regulator incorporates several protection fea-
tures which make it ideal for use in battery-powered circuits.
In addition to the normal protection features associated
with monolithic regulators, such as current limiting and
thermal limiting, the device is protected against reverse
input voltages, reverse output voltages and reverse voltages
from output to input. The two regulators have common