1 ns/DIV

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C001

9

LMH0302

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SNLS247H – APRIL 2007 – REVISED JUNE 2016

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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

REQUIREMENT

Input termination

Required; 49.9

Ω are recommended (see Figure 3).

Output AC-coupling capacitors

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.

DC power supply coupling capacitors

possible.

Distance from device to BNC

Keep this distance as short as possible.

High speed SDI and SDI trace impedance

Design differential trace impedance of SDI and SDI with 100

Ω.

High speed SDO and SDO trace impedance

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

Figure 4. SDO PRBS10 at 270 Mbps