LMH6552SD/NOPB National Semiconductor, LMH6552SD/NOPB Datasheet - Page 18

• Manufacturer Part Number: LMH6552SD/NOPB
• Description: IC AMP DIFF 1.5GHZ 1CN 8-LLP
• Manufacturer: National Semiconductor
• Series: LMH®, PowerWise®r

Specifications of LMH6552SD/NOPB

• Amplifier Type: Differential
• Number Of Circuits: 1
• Output Type: Differential
• Slew Rate: 3800 V/µs
• -3db Bandwidth: 1.5GHz
• Current - Input Bias: 60µA
• Voltage - Input Offset: 1500µV
• Current - Supply: 22.5mA
• Current - Output / Channel: 80mA
• Voltage - Supply, Single/dual (±): 4.5 V ~ 12 V, ±2.25 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-LLP
• For Use With: LMH6552SDEVAL - BOARD EVALUATION FOR LMH6552
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Gain Bandwidth Product: -
• Other names: LMH6552SD; LMH6552SD; LMH6552SDTR

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DRIVING CAPACITIVE LOADS
As noted previously, capacitive loads should be isolated from
the amplifier output with small valued resistors. This is par-
ticularly the case when the load has a resistive component
that is 500Ω or higher. A typical ADC has capacitive compo-
nents of around 10 pF and the resistive component could be
1000Ω or higher. If driving a transmission line, such as 50Ω
coaxial or 100Ω twisted pair, using matching resistors will be
sufficient to isolate any subsequent capacitance. For other
applications see the Suggested R
charts in the Typical Performance Characteristics section.
BALANCED CABLE DRIVER
With up to 15 V
of linear drive current the LMH6552 makes an excellent cable
driver as shown in
for driving differential cables from a single ended source.
POWER SUPPLY BYPASSING
The LMH6552 requires supply bypassing capacitors as
shown in
capacitors should be leadless SMT ceramic capacitors and
should be no more than 3 mm from the supply pins. These
capacitors should be star routed with a dedicated ground re-
turn plane or trace for best harmonic distortion performance.
A small capacitor, ~0.01 µF, placed across the supply rails,
and as close to the chip's supply pins as possible, can further
improve HD2 performance. Thin traces or small vias will re-
duce the effectiveness of bypass capacitors. Also shown in
both figures is a capacitor from the V
ground. These inputs are high impedance and can provide a
coupling path into the amplifier for external noise sources,
possibly resulting in loss of dynamic range, degraded CMRR,
degraded balance and higher distortion.
FIGURE 11. Fully Differential Cable Driver
Figure 12
PP
differential output voltage swing and 80 mA
Figure
and
Figure
11. The LMH6552 is also suitable
13. The 0.01 µF and 0.1 µF
OUT
CM
vs. Capacitive Load
and ENABLE pins to
30003502
18
POWER DISSIPATION
The LMH6552 is optimized for maximum speed and perfor-
mance in the small form factor of the standard SOIC package,
and is essentially a dual channel amplifier. To ensure maxi-
mum output drive and highest performance, thermal shut-
down is not provided. Therefore, it is of utmost importance to
make sure that the T
the overall power dissipation.
Follow these steps to determine the maximum power dissi-
pation for the LMH6552:
1.
2.
3.
The maximum power that the LMH6552 package can dissi-
pate at a given temperature can be derived with the following
equation:
P
(°C) and θ
MAX
FIGURE 13. Single Supply Bypassing Capacitors
Calculate the quiescent (no-load) power: P
(V
through the feedback network if V
Calculate the RMS power dissipated in each of the output
stages: P
− V
and the current measured at the output pins of the
differential amplifier as if they were single ended
amplifiers and V
Calculate the total RMS power: P
FIGURE 12. Split Supply Bypassing Capacitors
= (150° – T
S
), where V
−
OUT
JA
) * I
= Thermal resistance, from junction to ambient,
D
(rms) = rms ((V
−
AMB
OUT
S
= V
)/ θ
) , where V
S
JMAX
is the total supply voltage.
JA
+
- V
, where T
of 150°C is never exceeded due to
−
. (Be sure to include any current
S
OUT
- V
AMB
and I
+
OUT
= Ambient temperature
T
OCM
) * I
= P
OUT
is not mid-rail.)
AMP
+
30003501
are the voltage
OUT
30003512
AMP
+ P
) + rms ((V
D
= I
.
CC
*
S