TC1054 TelCom Semiconductor, TC1054 Datasheet - Page 11

• Manufacturer Part Number: TC1054
• Description: 50mA CMOS LDO WITH SHUTDOWN AND ERROR OUTPUT
• Manufacturer: TelCom Semiconductor

100mA CMOS LDO WITH SHUTDOWN
AND ERROR OUTPUT
is a function of the maximum ambient temperature (T
the maximum allowable die temperature (125 C) and the
thermal resistance from junction-to-air (
package has a
mounted on a single layer FR4 dielectric copper clad PC
board.
to ensure regulator thermal operation is within limits. For
example:
TC1055-01 6/5/97
I
Where:
V
LOAD MAX
V
OUT MIN
The maximum allowable power dissipation (Equation 2)
Equation 1 can be used in conjunction with Equation 2
Given:
Find:
Actual power dissipation:
Maximum allowable power dissipation:
IN MAX
P
Where all terms are previously defined.
P
D
D
V
= [(3.0 x 1.05) – (2.7 x .995)]40 x 10
= 18.5mW
= Worst case actual power dissipation
= Maximum voltage on V
= Minimum regulator output voltage
= Maximum output (load) current
V
OUT MIN
1. Actual power dissipation
2. Maximum allowable dissipation
(V
P
T
P
IN MAX
I
D
LOAD
AMAX
DMAX
IN MAX
P
D MAX
(V
JA
IN MAX
= 3.0V 5%
= 2.7V 0.5V
= 40mA
= 55 C
= (125 – 55)
= 318mW
= (T
– V
of approximately 220 C/Watt when
= (T
J MAX
OUT MIN
220
Equation 1.
Equation 2.
– V
J MAX
OUT MIN
– T
JA
) I
– T
LOAD MAX
A MAX
JA
J MAX )
) I
IN
LOAD MAX
)
JA
). SOT-23A-5
–3
A MAX
),
5
only 60mW; far below the allowable limit of 318mW. In a
similar manner, Equation 1 and Equation 2 can be used to
calculate maximum current and/or input voltage limits. For
example, the maximum allowable V
ing the maximum allowable power dissipation of 318mW
into Equation 1, from which V
Layout Considerations
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
crease the maximum allowable power dissipation limit.
In this example, the TC1055 dissipates a maximum of
The primary path of heat conduction out of the package
PRELIMINARY INFORMATION
IN MAX
IN
= 5.9V.
is found by substitut-
JA
and therefore in-
TC1055