LMH0302 Datasheet, PDF (9/18 Pages) Texas Instruments – 3-Gbps HD/SD SDI Cable Driver

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LMH0302
SNLS247H – APRIL 2007 – REVISED JUNE 2016
Typical Application (continued)
8.2.1 Design Requirements
For the LMH0302 design example, Table 1 lists the design parameters.
Table 1. LMH0302 Design Parameters
PARAMETER
Input termination
Output AC-coupling capacitors
DC power supply coupling capacitors
Distance from device to BNC
High speed SDI and SDI trace impedance
High speed SDO and SDO trace impedance
REQUIREMENT
Required; 49.9 Ω are recommended (see Figure 3).
Required; both SDO and SDO require AC-coupling capacitors. SDO AC-coupling capacitors
are expected to be 4.7 µF to comply with SMPTE wander requirement.
To minimize power supply noise, place 0.1-µF capacitor as close to the device V_CC pin as
possible.
Keep this distance as short as possible.
Design differential trace impedance of SDI and SDI with 100 Ω.
Single-ended trace impedance for SDO and SDO with 75 Ω.
8.2.2 Detailed Design Procedure
The following design procedure is recommended:
1. Select a suitable power supply voltage for the LMH0302. It can be powered from a single 3.3-V supply.
2. Check that the power supply meets the DC requirements in Electrical Characteristics – DC.
3. Select the proper pull-high or pull-low for SD/HD to set the slew rate.
4. Select proper pull-high or pull-low for ENABLE to enable or disable the output driver.
5. Choose a high-quality 75-Ω BNC that is capable to support 2.97-Gbps applications. Consult a BNC supplier
regarding insertion loss, impedance specifications, and recommended BNC footprint for meeting SMPTE
return loss requirements.
6. Choose small 0402 surface-mount ceramic capacitors for the AC-coupling and bypass capacitors.
7. Use proper footprint for BNC and AC-coupling capacitors. Anti-pads are commonly used in power and
ground planes under these landing pads to achieve optimum return loss.
8.2.3 Application Curves
1 ns/DIV
Figure 4. SDO PRBS10 at 270 Mbps
920
900
880
860
840
820
800
780
760
660
680
700
720
740
760
780
R_REF Resistance (Ÿ)
C001
Figure 5. SDO Amplitude vs R_REF Resistance
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