sy89540u Micrel Semiconductor, sy89540u Datasheet - Page 5

• Manufacturer Part Number: sy89540u
• Description: Precision Low Jitter 4x4 Lvds Crosspoint Switch With Internal Termination
• Manufacturer: Micrel Semiconductor

Functional Description
Buffer Mode
SY89540 can be used as a 1:4 fanout buffer. This is
the default mode with LOAD and CONFIG being
HIGH when the device is first powered up. The SIN0
and SIN1 inputs select the input signal that will be
buffered. Regardless of the output switch selection,
the input signal will be buffered to all four outputs.
Crosspoint Mode
SY89540 can be programmed to take differential
input signals from any input and buffer the signals to
one or more outputs. Prior to configuring SIN and
SOUT, LOAD and CONFIG must be LOW. To
program the desired I/O combination, follow the
following sequence:
December 2007
1) Select the desired input with the SIN0 and
2) Pulse the LOAD with a positive pulse to load
3) Pulse the CONFIG pin with a positive pulse
4) This method can be used to create
SIN1 inputs and the output with the SOUT0
and SOUT1.
SIN and SOUT.
to latched the I/O configuration.
independent paths between inputs and
outputs. Below is the truth table to create a
4:4 buffer where IN0 -> Q3, IN1 -> Q2, IN2 ->
Q1, and IN3 -> Q0:
Input
IN0
IN1
IN2
IN3
SIN1
0
0
1
1
SIN0
0
1
0
1
Table 1. 4:4 Buffer Truth Table
SOUT1
1
1
0
0
5
The SY89540 can be switched from crosspoint
mode to a 1:4 fanout buffer simply by providing a
LOW-to-HIGH pulse to the LOAD and CONFIG pins.
The input configuration (SIN0:1) will select the
desired input signal while the output switch will
buffer the selected input signal. To get the same
desired input to all four outputs (1:4), LOAD and
CONFIG must be repeated four times to cover all
outputs (i.e., SOUT0:1 must go through all four
output combinations, repeated by LOAD and
CONFIG).
SOUT0
1
0
1
0
Load
0
0
0
0
[e-mail]
Config.
0
0
0
0
or [phone]
M9999-120607-C
Output
Q3
Q2
Q1
Q0