LM7372MR/NOPB National Semiconductor, LM7372MR/NOPB Datasheet - Page 13

• Manufacturer Part Number: LM7372MR/NOPB
• Description: IC OPAMP DUAL HS HI OUTP 8-PSOP
• Manufacturer: National Semiconductor
• Series: VIP™ IIIr

Specifications of LM7372MR/NOPB

• Amplifier Type: Voltage Feedback
• Number Of Circuits: 2
• Slew Rate: 3000 V/µs
• Gain Bandwidth Product: 120MHz
• -3db Bandwidth: 220MHz
• Current - Input Bias: 2.7µA
• Voltage - Input Offset: 2000µV
• Current - Supply: 13mA
• Current - Output / Channel: 260mA
• Voltage - Supply, Single/dual (±): 9 V ~ 36 V, ±4.5 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-PSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• Other names: *LM7372MR; *LM7372MR/NOPB; LM7372MR

Figure 3 shows that there could be 1mA or more excess sup-
ply current per amplifier with close to full output swing
(24V
quencies when the output swing is less). This boost in supply
current enables the output to “keep up” with high frequency/
large signal output swing, but in turn, increases the total pack-
age power dissipation and therefore raises the device junction
temperature. As a consequence, these demanding applica-
tions, especially ones which run at higher supply voltages,
need special attention to the package heatsink design. For
that reason, Figure 3 has the safe operating limits for the
8-Pin PSOP package (e.g. “30V supply (2 amplifiers)” hori-
zontal line) superimposed on top of it (with T
when operated at 85°C ambient), so that the designer can
readily decide whether or not there is need for additional heat
sinking.
For example, if the LM7372 is operating similarly to Figure 1
schematic with a single power supply of 10V, Figure 3 shows
that it is safe to have up to 10V
with no additional heat sinking. This determination is from in-
spection of Figure 3 where the “10V supply (2 amplifiers)” safe
operating limit intercepts the 10V
40MHz. Use the “10V supply (1 amplifier)” safe operating limit
line in cases where the second amplifier in the LM7372 pack-
age does not experience high frequency/high output swing
conditions.
At any given “I
quency and output swing remains essentially constant for all
output swing plots. This holds true for the lower frequency
range before the plots experience a slope increase. There-
fore, if the application example just discussed operates up to
60MHz instead, it is possible to calculate the junction-
temperature-limited maximum output swing of 6.7V
(= 40MHz x 10V
Please note that Figure 3 precludes any additional amplifier
power dissipation related to load (this topic is discussed below
in detail). This load current, if large enough, will reduce the
operating frequency/output swing further. It is important to
note that the LM7372 can be destroyed if it is allowed to dis-
sipate enough power that compromises its maximum junction
temperature limit of 150°C.
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
PP
) when frequency is just above 1MHz (or at higher fre-
FIGURE 3. Power Supply Current Increase
S
PP
increase” value (y axis), the product of fre-
/60MHz) instead.
PP
output swing at up to 40MHz
PP
swing graph at around
J
limit of 140°C
20004930
PP
13
average value (due to a DC load current) and an AC compo-
nent. DC load current would flow if there is an output voltage
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:
Table 3 below shows the maximum AC component of the load
power dissipated by the op amp for standard Sinusoidal, Tri-
angular, and Square Waveforms:
TABLE 3. Normalized maximum AC Power Dissipated in
The table entries are normalized to V
computed at the output swing point where the amplifier dissi-
pation is the highest for each waveform type. To figure out the
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 output waveform, power dissipation in the
output stage is calculated as: P
46.9mW which contributes another 2.2°C (= 46.9mW x
47°C/W) rise to the LM7372 junction temperature in the 8-Pin
PSOP package.
POWER SUPPLIES
The LM7372 is fabricated on a high voltage, high speed pro-
cess. Using high supply voltages ensures adequate head-
room to give low distortion with large signal swings. In Figure
1, a single 24V supply is used. To maximize the output dy-
namic range the non-inverting inputs are biased to half supply
voltage by the resistive divider R1, R2. The input signals are
AC coupled and the coupling capacitors (C1, C2) can be
scaled with the bias resistors (R3, R4) to form a high pass
filter if unwanted coupling from the POTS signal occurs.
Supply decoupling is important at both low and high frequen-
cies. The 10µF Tantalum and 0.1µF Ceramic capacitors
should be connected close to the supply Pin 14. Note that the
V
(Pins 1,8,9 & 16) are at the same potential. Any layout should
avoid running input signal leads close to this ground plane, or
unwanted coupling of high frequency supply currents may
generate distortion products.
Although this application shows a single supply, conversion
to a split supply is straightforward. The half supply resistive
divider network is eliminated and the bias resistors at the non-
P
P
P
P
I
V
I
V
V
S
O
−
D(TOTAL)
Q
DC
AC
S
O
R
pin (pin 6), and the PCB area associated with the heatsink
= |I
50.7 x 10
Sinusoidal
= See Table 3 below
= |I
S
the Output Stage for Standard Waveforms
O
• V
= P
• (V
S
S
|
Supply Current
Total Supply Voltage (V
Average Load Current
Average Output Voltage
Reference Voltage (V
sinking current)
2
Q
R
−3
/R
+ P
- V
L
. For example, with ±5V supplies, a 100Ω
O
DC
)|
+ P
P
46.9 x 10
AC
AC
Triangular
(W.Ω/V
Op Amp Quiescent Power
Dissipation
DC Load Power
AC Load Power
AC
−3
= 46.9 x 10
+
2
)
for sourcing and V
S
+
2
/R
- V
L
−
. These entries are
)
62.5 x 10
−3
Square
www.national.com
x 10
2
−3
/100 =
−
for