AN17850A 데이터 시트보기 (PDF) - Panasonic Corporation
부품명
상세내역
제조사
AN17850A Datasheet PDF : 17 Pages
| |||
Prepared
Checked
Approved
Product Specifications
(Technical Data)
AN17850A
Ref No.
G-6
Total Page
17
Page No.
14
Power dissipation and Heat Sink
TA
TC
TJ
HEAT SINK CASE
DIE
Definition of terms
θCA
θJC
PD: Power Dissipation
Tj: Junction Temperature
FIG1. Simplified Illustration of IC
and Heat Sink attached
TC: Case Temperature
TA: Ambient Temperature
θJC: Thermal Resistance of junction to case
θCA: Thermal Resistance of case to ambient, normally through heat sink
The following two equations represent the relations of these terms.
( Tj - TC ) / θJC = PD
(1)
( TC - TA ) / θCA = PD’
(2)
For reliable and long-term, continuous operation, junction temperature should not
exceed 125OC and θJC for FP-12S package is 2OC/W. Substitute these values
in Equation 1. After specify the PD, TC can be determined.
Assume no heat loss at the casing,i.e. all power is dissipated to the ambient
through heat sink, which is quite true. So PD = PD’. Since TC is also known,
one can determine the following using equation2:
a) The rating of heat sink for specific maximum operating ambient temperature, or
b) The maximum operating ambient temperature for specific heat sink rating.
A more general equation can be used for rough calculation.
( TJ - TA ) / θJA = PD
(3)
θJA = θCA + θJC
(4)
In this case, θJA is total thermal resistance of the heat sink and IC package.
Therefore, for specified power dissipation, either heat sink rating or maximum
operating ambient temperature can be decided if the other is known.
Take note that it’s essential to know PD value before hand in order to work out
other quantities. PD calculation is as shown.
PD = Vcc x Icc - Po_total (5)
Vcc: DC supply voltage
Icc: RMS value of IC current
Po_total: Total output power
Eff. Date Eff. Date
15-AUG-03
FMSC-PSDA-002-01 REV 1
Eff. Date
Eff. Date
Semiconductor Company, Matsushita Electric Industrial Co., Ltd.
Share Link: 