LT3008ITS8#TRPBF Linear Technology, LT3008ITS8#TRPBF Datasheet - Page 15

• Manufacturer Part Number: LT3008ITS8#TRPBF
• Description: IC REG LDO ADJ 20MA TSOT23-8
• Manufacturer: Linear Technology

Specifications of LT3008ITS8#TRPBF

• Regulator Topology: Positive Adjustable
• Voltage - Output: 0.6 ~ 44.5 V
• Voltage - Input: 2 ~ 45 V
• Voltage - Dropout (typical): 0.3V @ 20mA
• Number Of Regulators: 1
• Current - Output: 20mA
• Current - Limit (min): 22mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-8, TSOT-8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
Table 3: Measured Thermal Resistance for TSOT-23 Package
For example, a 4-layer, 1 ounce copper PCB board with
3 thermal vias from the DFN exposed backside or the
3 fused TSOT-23 GND pins to inner layer GND planes
achieves 45°C/W thermal resistance. Demo circuit DC
1388A’s board layout achieves this 45°C/W performance.
This is approximately a 30% improvement over the lowest
numbers shown in Tables 2 and 3.
Calculating Junction Temperature
Example: Given an output voltage of 3.3V, an input voltage
range of 12V ±5%, an output current range of 0mA to 20mA
and a maximum ambient temperature of 85°C, what will
the maximum junction temperature be for an application
using the DC package?
The power dissipated by the device is equal to:
where,
*Device is mounted on the topside.
TOPSIDE*
2500mm
1000mm
225mm
100mm
I
I
V
I
50mm
OUT(MAX)
OUT(MAX)
GND
IN(MAX)
COPPER AREA
at (I
2
2
2
2
2
= 12.6V
OUT
(V
= 20mA
BACKSIDE
2500mm
2500mm
2500mm
2500mm
2500mm
IN(MAX)
= 20mA, V
2
2
2
2
2
– V
2500mm
2500mm
2500mm
2500mm
2500mm
OUT
BOARD
IN
AREA
= 12.6V) = 0.3mA
) + I
2
2
2
2
2
GND
(JUNCTION-TO-AMBIENT)
THERMAL RESISTANCE
(V
IN(MAX)
65°C/W
67°C/W
70°C/W
75°C/W
85°C/W
)
So,
P = 20mA(12.6V – 3.3V) + 0.3mA(12.6V) = 189.8mW
The thermal resistance ranges from 65°C/W to 85°C/W
depending on the copper area. So, the junction temperature
rise above ambient approximately equals:
The maximum junction temperature equals the maximum
junction temperature rise above ambient plus the maximum
ambient temperature or:
Protection Features
The LT3008 incorporates several protection features that
make it ideal for use in battery-powered circuits. In ad-
dition to the normal protection features associated with
monolithic regulators, such as current limiting and thermal
limiting, the device also protects against reverse-input
voltages, reverse-output voltages and reverse output-to-
input voltages.
Current limit protection and thermal overload protec-
tion protect the device against current overload condi-
tions at the output of the device. For normal operation,
do not exceed a junction temperature of 125°C. The
typical thermal shutdown circuitry temperature threshold
is 160°C.
The IN pin withstands reverse voltages of 50V. The device
limits current fl ow to less than 30μA (typically less than
1μA) and no negative voltage appears at OUT. The device
protects both itself and the load against batteries that are
plugged in backwards.
0.1898W(75°C/W) = 14.2°C
T
J(MAX)
= 85°C + 14.2°C = 99.2°C
LT3008 Series
15
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