Datasheet

OPA2690
www.ti.com SBOS238G –JUNE 2002–REVISED MARCH 2010
THERMAL ANALYSIS Note that it is the power in the output stage and not
into the load that determines internal power
Due to the high output power capability of the
dissipation.
OPA2690, heatsinking or forced airflow may be
required under extreme operating conditions. As a worst-case example, compute the maximum T
J
Maximum desired junction temperature will set the using an OPA2690ID (SO-8 package) in the circuit of
maximum allowed internal power dissipation as Figure 36 operating at the maximum specified
described below. In no case should the maximum ambient temperature of +85°C and with both outputs
junction temperature be allowed to exceed 150°C. driving a grounded 20Ω load to +2.5V.
Operating junction temperature (T
J
) is given by: P
D
= 10V × 12.6mA + 2 [5
2
/(4 × (20Ω || 804Ω))
T
A
+ P
D
× q
JA
P
D
= 766mW
The total internal power dissipation (P
D
) is the sum of
Maximum T
J
= +85°C + (0.766W × 125°C/W)
quiescent power (P
DQ
) and additional power
P
D
= 180°C
dissipated in the output stage (P
DL
) to deliver load
power. Quiescent power is simply the specified
This absolute worst-case condition exceeds the
no-load supply current times the total supply voltage
specified maximum junction temperature. Actual P
DL
across the part. P
DL
depends on the required output
is normally less than that considered here. Carefully
signal and load but, for a grounded resistive load, is
consider maximum T
J
in your application.
at a maximum when the output is fixed at a voltage
equal to 1/2 of either supply voltage (for equal bipolar
supplies). Under this condition, P
DL
= V
S2
/(4 × R
L
)
where R
L
includes feedback network loading.
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