LMH0001_10 Datasheet, PDF (1/4 Pages) National Semiconductor (TI) – Replacing the CLC001 Cable Driver with the LMH0001

Replacing the CLC001 Cable
National Semiconductor
Application Note 2059
Driver with the LMH0001
Gary Melchior
May 11, 2010
Introduction
The LMH0001 SD-SDI cable driver can replace the CLC001
cable driver in many applications. The LMH0001 and CLC001
are both cable drivers designed to drive 75Ω coaxial cable,
primarily for the SMPTE 259M interface. The supported data
rates are similar between the two devices. Both cable drivers
are powered from a 3.3V supply and rated for industrial tem-
perature range operation (-40°C to +85°C).
The LMH0001, the newer generation SDI cable driver, has
improved performance and is pin compatible with the
LMH0002 HD/SD-SDI cable driver and the LMH0302 3G/HD/
SD-SDI cable driver. This allows a forward migration path
from SD to HD to 3G. The LMH0001 provides improved output
return loss along with a 46% power savings over the CLC001,
with typical power of 125 mW in comparison with 231 mW for
the CLC001.
Table 1 shows the key differences between the CLC001 and
LMH0001.
TABLE 1. CLC001 and LMH0001 Key Differences
Supply Current (I_CC) (Typical)
Package
Data Rates
Output Rise/Fall Time (Typical)
ESD Rating
CLC001
70 mA
8-pin SOIC
DC to 622 Mbps
400 ps
≥±7 kV HBM
Input Interface
0.05V to 3.25V common mode
Output Interface
R_REF Resistor (800 mV_P-P Output)
Output Return Loss
Requires external 75Ω resistor to GND
1.91 kΩ to ground
Compliant to SMPTE spec
LMH0001
38 mA
16-pin LLP
DC to 540 Mbps
560 ps
≥±5 kV HBM
1.6V + V_SDI/2 to V_CC - V_SDI/2
common mode (self biased)
Requires external 75Ω resistor to V_CC
750Ω to V_CC
Meets SMPTE spec with margin
using recommended network
How To Replace the CLC001 with
the LMH0001
Replacing the CLC001 with the LMH0001 requires a few sim-
ple steps. The device packages and pinouts are different so
this change requires a new PCB layout. To replace the
CLC001 with the LMH0001, follow these steps:
1. Check the output common mode voltage of the driving
device to determine if it is compatible with the LMH0001
input common mode range—if so, it is preferred to DC
couple the inputs, and if not, add AC coupling capacitors
in series with the inputs, prior to the input termination.
When AC coupling, remove any bias applied to the inputs
as this is not required for the LMH0001 since the inputs
are self-biased.
2. Replace the 75Ω resistors to ground on the output with
75Ω resistors to V_CC. These pullup resistors should be
placed as close as possible to the LMH0001 output pins.
3. In order to meet the SMPTE return loss specification, add
a return loss network in series with the LMH0001 outputs.
This network typically consists of a 5.6 nH inductor in
parallel with a 75Ω resistor, immediately following the
75Ω pullup. If only one output is used, the return loss
network is not necessary on the unused output.
4. For SMPTE applications, change the output coupling
capacitor from 1 µF to 4.7 µF. Using this larger AC
coupling capacitor value is good practice when dealing
with the large DC shifts associated with the SMPTE
pathological signals.
5. For 800 mV_P-P output, change the R_REF resistor from
1.91 kΩ connected to ground to 750Ω connected to
V_CC. For 1.0 V_P-P output, change the R_REF resistor from
1.5 kΩ connected to ground to 590Ω connected to V_CC.
Figure 1 shows the typical application for the CLC001, and
Figure 2 shows the typical application for the LMH0001.
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