LMH0026_1 Datasheet, PDF (1/4 Pages) National Semiconductor (TI) – Replacing the CLC016 Replacing the CLC016 reclocker in many applications

Replacing the CLC016
National Semiconductor
Application Note 2004
Reclocker with the LMH0026 Gary Melchior
October 13, 2009
Introduction
The LMH0026 SD-SDI reclocker can replace the CLC016 re-
clocker in many applications. The LMH0026 and CLC016 are
both reclockers designed to recover and retime data, primarily
for the SMPTE 259M interface. Both reclockers are rated for
industrial temperature range operation (-40°C to +85°C).
The LMH0026, the newer generation SDI reclocker, has ad-
vanced features and is pin compatible with the LMH0046 HD-
SDI reclocker and the LMH0346 3G-SDI reclocker. This
allows a forward migration path from SD to HD to 3G. The
LMH0026 offers improved performance and extremely low
output jitter (half the output jitter of the CLC016 at 270 Mbps).
The LMH0026 also offers a lower supply voltage (3.3V), en-
abling system designers to migrate to lower-power designs.
The LMH0026 provides a 37% power savings over the
CLC016, with typical power of 330 mW in comparison with
525 mW for the CLC016.
Table 1 shows the key differences between the CLC016 and
LMH0026.
TABLE 1. CLC016 and LMH0026 Key Differences
Power Supply (V_CC)
Package
Data Rates
Output Jitter
ESD Rating
Input Interface
Output Structure
Loop Filter
CLC016
5.0V
28-pin PLCC or TSSOP
40 to 400 Mbps
150 ps_P-P
≥±2 kV HBM
2.5V to 5.0V common mode
Open collector, requires external 75Ω pullups to
5V
Three Components:
0.1 µF capacitor, 82 pF capacitor, 500Ω resistor
Rate Selection
Four selectable rates, auto or manual rate select
Other Features
Carrier detect
LMH0026
3.3V
20-pin e-TSSOP
270 Mbps
74 ps_P-P
≥±7 kV HBM
1.2V to 3.3V common mode
CML with internal 50Ω pullups (to 3.3V)
Single 56 nF capacitor
Single 270 Mbps rate operation, automatically
bypasses other rates
Bypass/Auto Bypass, choice of 2nd reclocked
data output or clock
How To Replace the CLC016 with
the LMH0026
Replacing the CLC016 with the LMH0026 requires a few sim-
ple steps. The device packages and pinouts are quite different
so this change requires a new PCB layout. To replace the
CLC016 with the LMH0026, follow these steps:
1. Change the power supply from 5V to 3.3V.
2. Replace the input termination with a single 100Ω
differential termination, located close to the LMH0026
input pins. Check the output common mode voltage of
the driving device to determine if it is compatible with the
LMH0026 input common mode range—if not, add AC
coupling capacitors in series with the input, prior to the
100Ω termination.
3. Removed the 75Ω pullups on the output and replace with
a 100Ω differential termination located at the input of the
next stage. The outputs may also be AC coupled, but no
pullups are required.
4. Change the loop filter circuit to a single 56 nF capacitor
between LF1 and LF2.
5. Add a 27 MHz crystal or suitable external clock
reference. Connect the crystal between the XTAL IN/
EXT CLK and XTAL OUT pins along with the 39 pF
capacitors as shown in the typical application in the
datasheet, or simply connect the 27 MHz external clock
to the XTAL IN/EXT CLK pin.
Figure 1 shows the typical application for the CLC016, and
Figure 2 shows the typical application for the LMH0026.
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