LMH6554_14 Datasheet, PDF (16/24 Pages) National Semiconductor (TI) – LMH6554 2.8 GHz Ultra Linear Fully Differential Amplifier

LMH6554
SNOSB30O – OCTOBER 2008 – REVISED MARCH 2013
www.ti.com
Balanced Cable Driver
With up to 5.68 V_PP differential output voltage swing the LMH6554 can be configured as a cable driver. The
LMH6554 is also suitable for driving differential cables from a single ended source as shown in Figure 36.
R_S = 50:
V_S
a
Input
Source
91:
76.8: ^VCM
91:
30.3:
200:
50:
+
LMH6554
-
2 V_PP
V_EN
200:
50:
100:
TWISTED PAIR
Figure 36. Fully Differential Cable Driver
Power Supply Bypassing
The LMH6554 requires supply bypassing capacitors as shown in Figure 37 and Figure 38. 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. Thin traces or small vias will reduce the effectiveness of bypass capacitors. Also shown
in both figures is a capacitor from the VCM and V_EN 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.
V⁺
0.1 PF 0.01 PF
10 PF
V_CM
+IN
-IN
0.1 PF
+
-OUT
LMH6554
-
+OUT
VEN
0.1 PF
V^-
0.1 PF 0.01 PF
10 PF
Figure 37. Split Supply Bypassing Capacitors
16
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