power supplies, this creates an internal dissipation of 11.4W.
This far exceeds the maximum rating and is not recom-
mended. If operation in this region is unavoidable, use the
DDPAK with a heat sink.
HEAT SINKING
Power dissipated in the OPA551 or OPA552 will cause the
junction temperature to rise. For reliable operation, the
junction temperature should be limited to +125°C. Many
applications will require a heat sink to assure that the
maximum operating junction temperature is not exceeded.
The heat sink required depends on the power dissipated and
on ambient conditions.
SAFE OPERATING AREA—8-PIN DIP
1000
For heat sinking purposes, the tab of the DDPAK is typically
soldered directly to a circuit board copper area. Increasing
the copper area improves heat dissipation. Figure 6 shows
typical thermal resistance from junction-to-ambient as a
function of copper area.
25°C
100
125°C
10
85°C
Depending on conditions, additional heat sinking may be
required. Aavid Thermal Products Inc. manufactures sur-
face-mountable heat sinks designed specifically for use with
DDPAK packages. Further information is available on
Aavid’s web site, www.aavid.com.
1
0.1
1
10
100
| VS | – | VO | (V)
To estimate the margin of safety in a complete design
(including heat sink), increase the ambient temperature until
the thermal protection is activated. Use worst-case load and
signal conditions. For good reliability, the thermal protec-
tion should trigger more than +25°C above the maximum
expected ambient condition of your application. This pro-
duces a junction temperature of +125°C at the maximum
expected ambient condition.
FIGURE 3. DIP-8 Safe Operating Area.
SAFE OPERATING AREA—SO-8
1000
25°C
100
10
1
THERMAL RESISTANCE vs
CIRCUIT BOARD COPPER AREA
50
125°C
85°C
OPA551, OPA552
Surface-Mount Package
1oz. copper
40
30
20
10
0
θ
0.1
1
10
| VS | – | VO | (V)
100
FIGURE 4. SO-8 Safe Operating Area.
0
1
2
3
4
5
Copper Area (inches2)
SAFE OPERATING AREA—DDPAK
25°C
1000
100
10
25°C
1" Copper
Circuit Board Copper Area
125°C
125°C
1" Copper
85°C
1
0.1
1
10
100
OPA551, OPA552
| VS | – | VO | (V)
Surface-Mount Package
FIGURE 5. DDPAK-7 Safe Operating Area.
FIGURE 6. DDPAK Thermal Resistance vs Circuit Board
Copper Area.
OPA551, OPA552
11
SBOS100A
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