
TAS5112
SLES048C  JULY 2003  REVISED MARCH 2004
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15
all cases. It is assumed that the thermal grease is 0.002
inch thick and that it is similar in performance to Wakefield
Type 126 thermal grease. It is important that the thermal
grease layer is
≤0.002 inches thick and that thermal pads
or tape are not used in the pad-to-heatsink interface due
to the high power density that results in these extreme
power cases.
Table 4. Case 1 (2
× 50 W Unclipped Into 6 ,
Both Channels in Same IC) (1)
56-Pin HTSSOP
Ambient temperature
25
°C
Power to load (per channel)
50 W (unclipped)
Power dissipation
4.5 W
Delta T inside package
10.2
°C, note 2 ×
channel dissipation
Delta T through thermal grease
37.1
°C, note 2 ×
channel dissipation
Required heatsink thermal resistance
4.2
°C/W
Junction temperature
110
°C
System RθJA
19
°C/W
RθJA * power dissipation
85
°C
Junction temperature
85
°C + 25°C = 110°C
(1) This case represents a stereo system with only one package. See
Case 2 and Case 2A if doing a full-power, 2-channel test in a
multichannel system.
Table 5. Case 2 (2
× 50 W Unclipped Into 6 ,
Channels in Separate Packages) (1)
56-Pin HTSSOP
Ambient temperature
25
°C
Power to load (per channel)
50 W (unclipped)
Power dissipation
4.5 W
Delta T inside package
5.1
°C
Delta T through thermal grease
18.6
°C
Required heatsink thermal resistance
6.9
°C/W
Junction temperature
110
°C
System RθJA
19
°C/W
RθJA * power dissipation
85
°C
Junction temperature
85
°C + 25°C = 110°C
(1) In this case, the power is separated into two packages. Note that
this allows a considerably smaller heatsink because twice as much
area is available for heat transfer through the thermal grease. For
this reason, separating the stereo channels into two ICs is
recommended in full-power stereo tests made on multichannel
systems.
Table 6. Case 2A (2
× 60 W Unclipped Into 6 ,
Channels in Separate IC Packages) (1)
56-Pin HTSSOP
Ambient temperature
25
°C
Power to load (per channel)
60 W (10% THD)
Power dissipation per channel
5.4 W
Delta T inside package
6.1
°C, note 2 ×
channel dissipation
Delta T through thermal grease
22.3
°C, note 2 ×
channel dissipation
Required heatsink thermal resistance
5.3
°C/W
Junction temperature
110
°C
System RθJA
15.9
°C/W
RθJA * power dissipation
85
°C
Junction temperature
85
°C + 25°C = 110°C
(1) In this case, the power is also separated into two packages, but
overdriving causes clipping to 10% THD. In this case, the high
power requires extreme care in attachment of the heatsink to
ensure that the thermal grease layer is
≤ 0.002 inches thick. Note
that this power level should not be attempted with both channels in
a single IC because of the high power density through the thermal
grease layer.
Thermal
Pad
8,20 mm
7,20 mm
3,90 mm
2,98 mm