MCP1726 Microchip Technology, MCP1726 Datasheet - Page 20

• Manufacturer Part Number: MCP1726
• Description: 1A Low Voltage / Low Quiescent Current LDO Regulator
• Manufacturer: Microchip Technology

MCP1726
Junction Temperature Estimate
To estimate the internal junction temperature, the
calculated temperature rise is added to the ambient or
offset temperature. For this example, the worst-case
junction temperature is estimated below:
As you can see from the result, this application will be
operating very near the maximum operating junction
temperature of 125°C. The PCB layout for this applica-
tion is very important as it has a significant impact on
the junction-to-ambient thermal resistance (R
the 3X3 DFN package, which is very important in this
application.
Maximum Package Power Dissipation at
70°C Ambient Temperature
From this table you can see the difference in maximum
allowable power dissipation between the 3X3 DFN
package and the 8-pin SOIC package. This difference
is due to the exposed metal tab on the bottom of the
DFN package. The exposed tab of the DFN package
provides a very good thermal path from the die of the
LDO to the PCB. The PCB then acts like a heatsink,
providing more area to distribute the heat generated by
the LDO.
DS21936B-page 20
3X3DFN (41° C/W R
SOIC8 (150°C/Watt R
P
P
P
P
D(MAX)
D(MAX)
D(MAX)
D(MAX)
T
T
T
J
J
J
= T
= 48.8°C + 70.0°C
= 118.8°C
= (125°C – 70°C) / 41° C/W
= 1.34W
= (125°C – 70°C)/ 150° C/W
= 0.366W
JRISE
JA
+ T
JA
)
)
A(MAX)
JA
) of
© 2005 Microchip Technology Inc.