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AS1156/AS1154

Data Sheet - A p p l i c a t i o n s

9 Applications

Figure 19. Typical Application Circuit

Power-Supply Bypassing

Differential Traces

Input trace characteristics can adversely affect the performance of the AS1156/AS1154.

Use controlled-impedance PC board traces to match the cable characteristic impedance. The termination resistor is

also matched to this characteristic impedance.

Eliminate reflections and ensure that noise couples as common mode by running the differential traces near each

other.

Reduce skew by using matched trace lengths. Tight skew control is required to minimize emissions and proper data

recovery of the devices.

Route each channel’s differential signals very close to each other for optimal cancellation of their respective exter-

nal magnetic fields. Use a constant distance between the differential traces to avoid irregularities in differential

impedance.

Avoid 90° turns (use two 45° turns).

Minimize the number of vias to further prevent impedance irregularities.

Cables and Connectors

Supported transmission media include printed circuit board traces, backplanes, and cables.

Use cables and connectors with matched differential impedance (typically 100

Ω) to minimize impedance mis-

matches.

Balanced cables such as twisted pair offer superior signal quality and tend to generate less EMI due to magnetic

field canceling effects. Balanced cables pick up noise as common mode, which is rejected by the LVDS receiver.

Avoid the use of unbalanced cables such as ribbon cable or simple coaxial cable.

Table 5. Function Table

Input

Output

INx

OUTx+

OUTx-

LL

H

H

HL

Undetermined

Undetermined

LVDS

Signals

107

Ω

LVTTL/LVCMOS

Data Inputs

LVTTL/LVCMOS

Data Outputs

100

Ω Shielded Twisted Cable or Microstrip PC Board Traces

Tx

Rx

AS1158

Single LVDS Receiver

AS1156

0.1µF

0.001µF

+3.3V

0.1µF

0.001µF

+3.3V