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.
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.
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.
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.
SAFE OPERATING AREA—8-PIN DIP
1000
25°C
100
I
O
(mA)
125°C
10
85°C
1
0.1
1
10
| V
S
| – | V
O
| (V)
100
FIGURE 3. DIP-8 Safe Operating Area.
SAFE OPERATING AREA—SO-8
1000
25°C
100
I
O
(mA)
125°C
10
85°C
Thermal Resistance,
θ
JA
(°C/W)
50
THERMAL RESISTANCE vs
CIRCUIT BOARD COPPER AREA
1
40
OPA551, OPA552
Surface-Mount Package
1oz. copper
30
0.1
1
10
| V
S
| – | V
O
| (V)
100
20
FIGURE 4. SO-8 Safe Operating Area.
10
0
0
1
2
3
4
5
SAFE OPERATING AREA—DDPAK
1000
25°C
100
I
O
(mA)
Copper Area (inches
2
)
25°C
1" Copper
Circuit Board Copper Area
125°C
10
125°C
1" Copper
85°C
1
0.1
1
10
| V
S
| – | V
O
| (V)
100
OPA551, OPA552
Surface-Mount Package
FIGURE 5. DDPAK-7 Safe Operating Area.
FIGURE 6. DDPAK Thermal Resistance vs Circuit Board
Copper Area.
www.ti.com
OPA551, OPA552
SBOS100A
11
TI [ TEXAS INSTRUMENTS ]
