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TC1014-5.0VCT View Datasheet(PDF) - TelCom Semiconductor Inc => Microchip

Part Name
Description
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TC1014-5.0VCT
TelCom-Semiconductor
TelCom Semiconductor Inc => Microchip TelCom-Semiconductor
TC1014-5.0VCT Datasheet PDF : 10 Pages
1 2 3 4 5 6 7 8 9 10
PRELIMINARY INFORMATION
100mA CMOS LDO WITH SHUTDOWN
AND REFERENCE BYPASS
TC1015
PD (VINMAX VOUTMIN)ILOADMAX
Where:
PD = Worst case actual power dissipation
VINMAX = Maximum voltage on VIN
VOUTMIN = Minimum regulator output voltage
ILOADMAX = Maximum output (load) current
Equation 1.
The maximum allowable power dissipation (Equation 2)
is a function of the maximum ambient temperature (TAMAX),
the maximum allowable die temperature (125°C) and the
thermal resistance from junction-to-air (θJA). The
SOT-23A-5 package has a θJA of approximately 220°C/Watt
when mounted on a single layer FR4 dielectric copper clad
PC board.
In this example, the TC1015 dissipates a maximum of
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 VIN is found by sustituting
the maximum allowable power dissipation of 318mW into
Equation 1, from which VINMAX = 5.9V.
Layout Considerations
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 θJA and, therefore,
increase the maximum allowable power dissipation limit.
PD MAX = (TJMAX – TJMAX)
θJA
Where all terms are previously defined.
Equation 2.
Equation 1 can be used in conjunction with Equation 2
to ensure regulator thermal operation is within limits. For
example:
Given:
VINMAX = 3.0V ±10%
VOUTMIN = 2.7V ±0.5V
ILOAD = 98mA
TAMAX = 55°C
Find: 1. Actual power dissipation
2. Maximum allowable dissipation
Actual power dissipation:
PD (VINMAX VOUTMIN)ILOADMAX
= [(3.0 x 1.1) – (2.7 x .995)]98 x 10–3
= 60mW
Maximum allowable power dissipation:
PDMAX = (TJMAX – TAMAX)
θJA
= (125 – 55)
220
= 318mW
TC1015-01-6/5/97
4
 

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