Texas Instruments MuxIt-EVM Evaluation Module MUXIT-EVM MUXIT-EVM 데이터 시트
제품 코드
MUXIT-EVM
PC Board Layout Considerations
5-5
System Design Issues
Like the clock signals, the propagation delay of data signal interfaces also
have to be related. The remaining critical propagation delays for Figure 5–1
are given by:
have to be related. The remaining critical propagation delays for Figure 5–1
are given by:
t
pd(LCO)
= t
pd(CASCADE_DO)
t
pd(CASCADE_DO)
+ t
pd(A1:MC2)
= t
pd(SERIAL_DO)
+ t
pd(A1:MC3)
and for Figure 5–2 are given by:
t
pd(CASCADE_DI)
= t
pd(LCI1)
t
pd(SERIAL_DI)
= t
pd(LCI3)
In addition to trace length matches, the user must also be aware of stubs
present on multidrop lines and keep these stub lengths to a minimum. Each
line to a multiple drop input from the LVDS link is called a stub and contributes
to reflections on the link. Stubs are present in the MuxIt EVM multidrop lines.
These lines include the LCRO/LCRI and MCO/MCI lines on the serializer
board and CRI/LCI and MCO/MCI lines on the deserializer boards. Both
boards provide examples of how to minimize stub lengths. The serializer board
uses fly-by routing on the signal layer that distributes these signals, and the
vias needed to bring the signals to the top layer and the devices act as the
stubs. The deserializer also uses fly-by routing for most of the signal
distribution. The exceptions are traces from the A2:U1 LCI, the A2:U4 CRI, and
A2:U4 MCI. The traces of A2:U4 are relatively long to the terminations, as
compared to similar terminations on the serializer board. All stub lengths are
within the acceptable limit of 2 to 3 cm given in application note SLLA014A.
In general all signal terminations should be kept close to the input of a device,
even in point-to-point signals. The A2:U1 LCI signal is split at A2:TP2 and the
resulting stub is the trace running from A2:TP2 to the A2:U1 input. Figures 5–3
and 5–4 show the fly-by routing and the stubs present on the MCO and LCI
lines of the serializer and deserializer boards.
present on multidrop lines and keep these stub lengths to a minimum. Each
line to a multiple drop input from the LVDS link is called a stub and contributes
to reflections on the link. Stubs are present in the MuxIt EVM multidrop lines.
These lines include the LCRO/LCRI and MCO/MCI lines on the serializer
board and CRI/LCI and MCO/MCI lines on the deserializer boards. Both
boards provide examples of how to minimize stub lengths. The serializer board
uses fly-by routing on the signal layer that distributes these signals, and the
vias needed to bring the signals to the top layer and the devices act as the
stubs. The deserializer also uses fly-by routing for most of the signal
distribution. The exceptions are traces from the A2:U1 LCI, the A2:U4 CRI, and
A2:U4 MCI. The traces of A2:U4 are relatively long to the terminations, as
compared to similar terminations on the serializer board. All stub lengths are
within the acceptable limit of 2 to 3 cm given in application note SLLA014A.
In general all signal terminations should be kept close to the input of a device,
even in point-to-point signals. The A2:U1 LCI signal is split at A2:TP2 and the
resulting stub is the trace running from A2:TP2 to the A2:U1 input. Figures 5–3
and 5–4 show the fly-by routing and the stubs present on the MCO and LCI
lines of the serializer and deserializer boards.
Figure 5–3. Serializer Board MCO Trace Routing
SN65LVDS150 (U1)
Layer1
Stub
TP2
MCO
Fly-by Routing
SN65LVDS151 (U2)
Layer6
Serializer Board
SN65LVDS151 (U3)
MCI Termination
Resistor
R4
SN65LVDS151 (U4)