LMH6553 Datasheet, PDF (21/24 Pages) National Semiconductor (TI) – 900 MHz Fully Differential Amplifier With Output Limiting Clamp

High Speed Differential Amplifiers to Drive ADCs. For more
information regarding a particular ADC, refer to the particular
ADC datasheet for details.
TABLE 3. DIFFERENTIAL INPUT ADCs COMPATIBLE
WITH LMH6553 DRIVER
Product Number
Max
Sampling
Rate
(MSPS)
Resolution Channels
ADC1173
15
8
SINGLE
ADC1175
20
8
SINGLE
ADC08351
42
8
SINGLE
ADC1175-50
50
8
SINGLE
ADC08060
60
8
SINGLE
ADC08L060
60
8
SINGLE
ADC08100
100
8
SINGLE
ADC08200
200
8
SINGLE
ADC08500
500
8
SINGLE
ADC081000
1000
8
SINGLE
ADC08D1000
1000
8
DUAL
ADC10321
20
10
SINGLE
ADC10D020
20
10
DUAL
ADC10030
27
10
SINGLE
ADC10040
40
10
DUAL
ADC10065
65
10
SINGLE
ADC10DL065
65
10
DUAL
ADC10080
80
10
SINGLE
ADC11DL066
66
11
DUAL
ADC11L066
66
11
SINGLE
ADC11C125
125
11
SINGLE
ADC11C170
170
11
SINGLE
ADC12010
10
12
SINGLE
ADC12020
20
12
SINGLE
ADC12040
40
12
SINGLE
ADC12D040
40
12
DUAL
ADC12DL040
40
12
DUAL
ADC12DL065
65
12
DUAL
ADC12DL066
66
12
DUAL
ADC12L063
63
12
SINGLE
ADC12C080
80
12
SINGLE
ADC12DS080
80
12
DUAL
ADC12L080
80
12
SINGLE
ADC12C105
105
12
SINGLE
ADC12DS105
105
12
DUAL
ADC12C170
170
12
SINGLE
ADC14L020
20
14
SINGLE
ADC14L040
40
14
SINGLE
ADC14C080
80
14
SINGLE
ADC14DS080
80
14
DUAL
ADC14C105
105
14
SINGLE
ADC14DS105
105
14
DUAL
ADC14155
155
14
SINGLE
DRIVING CAPACITIVE LOADS
As noted previously, capacitive loads should be isolated from
the amplifier outputs 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_OUT vs. Capacitive Load
charts in the Typical Performance Characteristics section.
BALANCED CABLE DRIVER
With up to 8 V_PP differential output voltage swing and 100 mA
of linear drive current the LMH6553 makes an excellent cable
driver as shown in Figure 12. The LMH6553 is also suitable
for driving differential cables from a single ended source.
30043702
FIGURE 12. Fully Differential Cable Driver
POWER SUPPLY BYPASSING
The LMH6553 requires supply bypassing capacitors as
shown in Figure 13 and Figure 14. The 0.01 µF and 0.1 µF
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. Narrow traces or small vias will
reduce the effectiveness of bypass capacitors. Also shown in
both figures is a capacitor from the V_CM and V_CLAMP pins to
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.
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