TC1107 MICROCHIP [Microchip Technology], TC1107 Datasheet - Page 5

• Manufacturer Part Number: TC1107
• Description: 300mA CMOS LDO with Shutdown and VREF Bypass
• Manufacturer: MICROCHIP [Microchip Technology]

4.0
4.1
Integrated thermal protection circuitry shuts the
regulator off when die temperature exceeds 150°C.
The regulator remains off until the die temperature
drops to approximately 140°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 160°C/Watt, while the 8-Pin MSOP
package has a θ
©
A
JA
J
2002 Microchip Technology Inc.
MAX
MAX
I
Where:
V
LOAD
). The 8-Pin SOIC package has a θ
OUT
V
) and the thermal resistance from junction-to-air
), the maximum allowable die temperature
IN
MAX
MAX
THERMAL CONSIDERATIONS
Thermal Shutdown
Power Dissipation
P
MIN
D
= Worst case actual power dissipation
= Maximum voltage on V
= Minimum regulator output voltage
= Maximum output (load) current
P
D
≈ (V
JA
of approximately 200°C/Watt.
IN
MAX
– V
OUT
MIN
)I
LOAD
IN
MAX
JA
of
EQUATION 4-2:
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 TC1107 dissipates a maximum of
167mW; 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
≈ (V
= [(3.0 x 1.1) – (2.7 x .975)]250 x 10
= 167mW
V
V
I
T
T
8-Pin MSOP Package
LOAD
P
A
OUT
J
IN
2. Maximum allowable dissipation
MAX
MAX
D
IN
Where all terms are previously defined.
MAX
MAX
Layout Considerations
MAX
MIN
MAX
= (125 – 55)
= 318mW
= (T
– V
= 3.0V + 10%
= 2.7V – 2.5%
= 250mA
= 125°C
= 55°C
P
J
D
OUT
MAX
220
MAX
θ
MIN
– T
JA
= (T
)I
A
LOAD
MAX
J
MAX
θ
)
JA
MAX
– T
A
MAX
TC1107
)
JA
DS21356B-page 5
–3
and therefore