TC2015 Microchip Technology, TC2015 Datasheet - Page 11

• Manufacturer Part Number: TC2015
• Description: (TC2xxx) 50 mA / 100 mA / 150 mA CMOS LDOs with Shutdown and Reference Bypass
• Manufacturer: Microchip Technology

5.0
5.1
The amount of power the regulator dissipates is prima-
rily a function of input voltage, output voltage and
output current.
The following equation is used to calculate worst-case
power dissipation:
EQUATION
The maximum allowable power dissipation (P
a function of the maximum ambient temperature
(T
(T
tion-to-air (
of approximately 220°C/Watt when mounted on a
typical two layer FR4 dielectric copper clad PC board.
EQUATION
Where:
P
V
V
I
AMAX
JMAX
2003 Microchip Technology Inc.
LMAX
D
INMAX
OUTMIN
Where all terms are previously defined.
) (+125°C) and the thermal resistance from junc-
), the maximum allowable die temperature
THERMAL CONSIDERATIONS
Power Dissipation
P
JA
D
= Worst-case actual power dissipation
= Maximum voltage on V
= Minimum regulator output voltage
= Maximum output (load) current
). The 5-Pin SOT-23A package has a
P
DMAX
V
INMAX
=
T
-------------------------------------- -
–
JMAX
V
OU TMIN
–
JA
T
AMAX
I
LMAX
IN
DMAX
) is
JA
The P
P
is within limits. For example:
Actual power dissipation:
Maximum allowable power dissipation:
In this example, the TC2014 dissipates a maximum of
only 26.7 mW; far below the allowable limit of 318 mW.
In a similar manner, the P
tion can be used to calculate maximum current and/or
input voltage limits.
5.2
The primary path of heat conduction out of the package
is via the package leads. Therefore, layouts having a
ground plane, wide traces at the pads and wide power
supply bus lines combine to lower
increase the maximum allowable power dissipation
limit.
Given:
Find:
DMAX
V
V
I
T
T
1. Actual power dissipation
2. Maximum allowable dissipation
LOADMAX
D
P
AMAX
JMAX
INMAX
OUTMIN
TC2014/2015/2185
equation to ensure regulator thermal operation
D
equation can be used in conjunction with the
Layout Considerations
=
=
=
--------------------------------------------------------------------------------------------
26.7mW
V
P
3.0
INMAX
DMAX
= 3.0V +10%
= 2.7V – 2.5%
= 40 mA
= +125°C
= +55°C
1.1
–
=
=
=
V
–
OU TMIN
T
-------------------------------------- -
125 55
-------------------- -
318mW
D
JMAX
2.7
220
equation and P
220
–
–
JA
0.975
I
T
LMAX
AMAX
DS21662C-page 11
JA
40
and, therefore,
DMAX
10
–
3
equa-