Datasheet

V
IN
V
CM
V
CLAMP
100:
TWISTED PAIR
50:
2 V
PP
275:
127:
A
V
= 2 V/V
50:
a
+
-
275:
127:
28.7:
61.8:
R
S
= 50:
LMH6553
www.ti.com SNOSB07H –SEPTEMBER 2008–REVISED MARCH 2013
Table 3. DIFFERENTIAL INPUT ADCs COMPATIBLE WITH LMH6553 DRIVER (continued)
Product Number Max Sampling Rate (MSPS) Resolution Channels
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 particularly the case when the load has a resistive component that is 500Ω or higher. A typical ADC has
capacitive components 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.
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 65. The LMH6553 is also suitable for driving differential cables from a
single ended source.
Figure 65. Fully Differential Cable Driver
POWER SUPPLY BYPASSING
The LMH6553 requires supply bypassing capacitors as shown in Figure 66 and Figure 67. 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 return 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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