AMC1117 Datasheet, PDF (7/9 Pages) List of Unclassifed Manufacturers – 1A Low Dropout Positive Regulator

AMC1117
Application Note:
Maximum Power Calculation:
P_D(MAX)=
T_J(MAX) – T_A(MAX)
θ_JA
T_J(^OC): Maximum recommended junction temperature
T_A(^OC): Ambient temperature of the application
θ_JA(^OC/W): Junction-to-junction temperature thermal resistance of the package, and other heat dissipating
materials.
The maximum power dissipation of a single-output regulator :
P_D(MAX) = [(V_IN(MAX) - V_OUT(NOM))] × I_OUT(NOM) + V_IN(MAX) × I_Q
Where:
Then
V_OUT(NOM) = the nominal output voltage
I_OUT(NOM) = the nominal output current, and
I_Q = the quiescent current the regulator consumes at I_OUT(MAX)
V_IN(MAX) = the maximum input voltage
θ_JA = (150 ^OC – T_A)/ P_D
Thermal consideration:
When power consumption is over about 404 mW (for SOT-223 package, 687mW for TO-252 package, at T_A=70 ^OC),
additional heat sink is required to control the junction temperature below 125 ^OC.
The junction temperature is: T_J = P _D (θ_JT + θ_CS + θ_SA) + T_A
P _D: Dissipated power.
θ_JT: Thermal resistance from the junction to the mounting tab of the package.
θ_CS: Thermal resistance through the interface between the IC and the surface on which it is mounted. (Typically,
θ_CS < 1.0°C/W)
θ_SA: Thermal resistance from the mounting surface to ambient (thermal resistance of the heat sink).
If PC Board copper is going to be used as a heat sink, below table can be used to determine the appropriate size of
copper foil required. For multi-layered PCB, these layers can also be used as a heat sink. They can be connected with
several through hole vias.
PCB θ_SA (^OC /W)
59
PCB heat sink size (mm²) 500
45
1000
38
1500
33
2000
27
3000
24
4000
21
5000
Recommended figure of PCB area used as a heat sink.
through hole vias
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Copyright © 2006 ADDtek Corp.
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DD004_K -- JULY 2006