300mA C-MOS L.D.O. Regulator
LM1108F/SF
EQUATION 2-2:
Table 2-1 shows various values of
θJA
for the LM1108 versus board copper area.
TABLE 2-1 : THERMAL RESISTANCE GUIDELINES FOR LM1108
Equation 2-1can be used in conjunction with Equation 2-2 to ensure regulator thermal operation is within limits.
Forexample:
In this example, the LM1108 dissipates a maximum of 260mW; below the allow able limit of 508 mW . In a
similar manner, Equation 2-1 and Equation 2-2 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 508 mW into Equation 2-1, from which VINMAX = 4.6V.
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