TC1015 MICROCHIP [Microchip Technology], TC1015 Datasheet - Page 7

• Manufacturer Part Number: TC1015
• Description: 50mA, 100mA and 150mA CMOS LDOs with Shutdown and Reference Bypass
• Manufacturer: MICROCHIP [Microchip Technology]

4.0
4.1
Integrated thermal protection circuitry shuts the
regulator off when die temperature exceeds 160°C.
The regulator remains off until the die temperature
drops to approximately 150°C.
4.2
The amount of power the regulator dissipates is
primarily a function of input and output voltage, and
output current. The following equation is used to
calculate worst case actual power dissipation:
EQUATION 4-1:
The maximum allowable power dissipation (Equation
4-2) is a function of the maximum ambient temperature
(T
(T
(θ
approximately 220°C/Watt.
EQUATION 4-2:
©
A
JA
J
2002 Microchip Technology Inc.
MAX
MAX
I
Where:
LOAD
). The 5-Pin SOT-23A package has a θ
V
V
OUT
), the maximum allowable die temperature
) and the thermal resistance from junction-to-air
Where all terms are previously defined.
IN
THERMAL CONSIDERATIONS
Thermal Shutdown
Power Dissipation
MAX
MAX
P
MIN
D
P
= Worst case actual power dissipation
= Maximum voltage on V
= Minimum regulator output voltage
= Maximum output (load) current
D
P
≈ (V
D
MAX
IN
MAX
= (T
– V
J
MAX
θ
OUT
JA
– T
MIN
A
MAX
)I
LOAD
)
IN
MAX
JA
of
TC1014/TC1015/TC1185
Equation 4-1 can be used in conjunction with Equation
4-2 to ensure regulator thermal operation is within
limits. For example:
Given:
Find: 1. Actual power dissipation
Actual power dissipation:
P
Maximum allowable power dissipation:
In this example, the TC1014 dissipates a maximum of
26.7mW; below the allowable limit of 318mW. In a
similar manner, Equation 4-1 and Equation 4-2 can be
used to calculate maximum current and/or input
voltage limits.
4.3
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 θ
increase the maximum allowable power dissipation
limit.
D
= [(3.0 x 1.1) – (2.7 x .975)]40 x 10
= 26.7mW
≈ (V
P
V
V
I
T
T
LOAD
D
A
OUT
J
IN
2. Maximum allowable dissipation
MAX
MAX
MAX
IN
MAX
Layout Considerations
MAX
MIN
MAX
= (125 – 55)
= 318mW
= (T
– V
J
= 3.0V +10%
= 2.7V – 2.5%
= 40mA
= 125°C
= 55°C
MAX
220
OUT
θ
– T
JA
MIN
A
)I
MAX
LOAD
)
MAX
JA
DS21335B-page 7
–3
and therefore