lm7332mmx National Semiconductor Corporation, lm7332mmx Datasheet - Page 16

• Manufacturer Part Number: lm7332mmx
• Description: Dual Rail-to-rail Input/output 30v, Wide Voltage Range, High Output Operational Amplifier
• Manufacturer: National Semiconductor Corporation

www.national.com
FIGURE 2. Steady State Output Sourcing Characteristics
OUTPUT SHORT CIRCUIT CURRENT AND DISSIPATION
ISSUES
The LM7332 output stage is designed for maximum output
current capability. Even though momentary output shorts to
ground and either supply can be tolerated at all operating
voltages, longer lasting short conditions can cause the junc-
tion temperature to rise beyond the absolute maximum rating
of the device, especially at higher supply voltage conditions.
Below supply voltage of 6V, the output short circuit condition
can be tolerated indefinitely.
With the op amp tied to a load, the device power dissipation
consists of the quiescent power due to the supply current flow
into the device, in addition to power dissipation due to the load
current. The load portion of the power itself could include an
average value (due to a DC load current) and an AC compo-
nent. DC load current would flow if there is an output voltage
FIGURE 3. Steady State Output Sinking Characteristics
with Load Lines
with Load Lines
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offset, or the output AC average current is non-zero, or if the
op amp operates in a single supply application where the out-
put is maintained somewhere in the range of linear operation.
Therefore:
where:
I
V
V
V
Table 1 below shows the maximum AC component of the load
power dissipated by the op amp for standard Sinusoidal, Tri-
angular, and Square Waveforms:
TABLE 1. Normalized AC Power Dissipated in the Output
The table entries are normalized to V
AC load current component of power dissipation, simply mul-
tiply the table entry corresponding to the output waveform by
the factor V
load, and triangular waveform power dissipation in the output
stage is calculated as:
The maximum power dissipation allowed at a certain temper-
ature is a function of maximum die junction temperature (T
(MAX)
resistance from junction to ambient, θ
For the LM7332, the maximum junction temperature allowed
is 150°C at which no power dissipation is allowed. The power
capability at 25°C is given by the following calculations:
For MSOP package:
For SOIC package:
P
P
P
P
S
S
O
r
: Supply Current
TOTAL
Q
DC
AC
: V
: Total Supply Voltage (V
: Average Output Voltage
= I
50.7 x 10
) allowed, ambient temperature T
= See Table 1 below
+
Sinusoidal
= I
for sourcing and V
S
O
= P
· V
P
· (V
AC
S
Q
S
2
r
+ P
Stage for Standard Waveforms
−3
/R
= (46.9 x 10
- V
L
DC
. For example, with ±12V supplies, a 600Ω
o
)
+ P
AC
P
46.9 x 10
−
AC
Triangular
−3
for sinking current
+
) · [24
(W.Ω/V
− V
−
2
Op Amp Quiescent Power
)
−3
/600] = 45.0 mW
2
)
A
S
JA
, and package thermal
2
/R
.
L
. To figure out the
DC Load Power
AC Load Power
62.5 x 10
Square
Dissipation
−3
J