Datasheet

V
CM
V
+
10 PF
0.1 PF
+
-
0.1 PF
0.01 PF
0.01 PF
ENABLE
LMH6552
www.ti.com SNOSAX9H –APRIL 2007–REVISED MARCH 2013
Figure 56. Single Supply Bypassing Capacitors
POWER DISSIPATION
The LMH6552 is optimized for maximum speed and performance in the small form factor of the standard SOIC
package, and is essentially a dual channel amplifier. To ensure maximum output drive and highest performance,
thermal shutdown is not provided. Therefore, it is of utmost importance to make sure that the T
JMAX
of 150°C is
never exceeded due to the overall power dissipation.
Follow these steps to determine the maximum power dissipation for the LMH6552:
1. Calculate the quiescent (no-load) power:
P
AMP
= I
CC
* (V
S
)
where
• V
S
= V
+
- V
−
. (Be sure to include any current through the feedback network if V
OCM
is not mid-rail.) (1)
2. Calculate the RMS power dissipated in each of the output stages:
P
D
(rms) = rms ((V
S
- V
+
OUT
) * I
+
OUT
) + rms ((V
S
− V
−
OUT
) * I
−
OUT
)
where
• V
OUT
and I
OUT
are the voltage and the current measured at the output pins of the differential amplifier as if they were
single ended amplifiers and V
S
is the total supply voltage (2)
3. Calculate the total RMS power:
P
T
= P
AMP
+ P
D
(3)
The maximum power that the LMH6552 package can dissipate at a given temperature can be derived with the
following equation:
P
MAX
= (150° – T
AMB
)/ θ
JA
where
• T
AMB
= Ambient temperature (°C)
• θ
JA
= Thermal resistance, from junction to ambient, for a given package (°C/W)
• For the SOIC package θ
JA
is 150°C/W
• For WSON package θ
JA
is 58°C/W (4)
NOTE
If V
CM
is not 0V then there will be quiescent current flowing in the feedback network. This
current should be included in the thermal calculations and added into the quiescent power
dissipation of the amplifier.
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