MSK0002RH Datasheet, PDF (3/7 Pages) M.S. Kennedy Corporation – RAD TOLERANT, HIGH SPEED, BUFFER AMPLIFIER

APPLICATION NOTES
HEAT SINKING
To determine if a heat sink is necessary for your application
and if so, what type, refer to the thermal model and governing
equation below.
Thermal Model:
RΘSA = ((TJ - TA)/PD) - (RΘJC) - (RΘCS)
= ((125°C - 80°C) / 0.36W) - 55°C/W - 0.15°C/W
= 125 - 55.15
= 69.9°C/W
This heat sink in this example must have a thermal resistance
of no more than 69.9°C/W to maintain a junction temperature
of no more than +125°C.
Typical Applications:
Governing Equation:
TJ=PD X (RΘJC +RΘCS +RΘSA) +TA
Where
TJ=Junction Temperature
PD=Total Power Dissipation
RΘJC=Junction to Case Thermal Resistance
RΘCS=Heat Sink to Ambient Thermal Resistance
TC=Case Temperature
TA=Ambient Temperature
TS=Sink Temperature
Example:
This example demonstrates a worst case analysis for the buffer
output stage. This occurs when the output voltage is 1/2 the
power supply voltage. Under this condition, maximum power
transfer occurs and the output is under maximum stress.
Conditions:
VCC= ±12VDC
Vo= ±6Vp Sine Wave, Freq. = 1KHz
RL= 100Ω
For a worst case analysis we will treat the ±6Vp sine wave as
an 6 VDC output voltage.
1.) Find Driver Power Dissipation
PD= (Vcc-Vo) (Vo/RL)
= (12V-6V) (6V/100Ω)
= 360mW
2.) For conservative design, set TJ=+125°C Max.
3.) For this example, worst case TA=+80°C
4.) RΘJC = 55° C/W from MSK 0002RH Data Sheet
5.) RΘCS = 0.15° C/W for most thermal greases
6.) Rearrange governing equation to solve for RΘSA
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Rev. A 4/07