SY100E446(1998) データシートの表示（PDF） - Micrel
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SY100E446 Datasheet PDF : 8 Pages
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Micrel
SY10E446
SY100E446
APPLICATIONS INFORMATION
The SY10E/100E446 are integrated 4:1 parallel-to-serial
converters. The chips are designed to work with the E445
device to provide both transmission and receiving of a high-
speed serial data path. The E446 can convert 4 bits of
data into a 1.3Gb/s NRZ data stream. The device features
a SYNC input which allows the user to reset the internal
clock circuitry and restart the conversion sequence (see
Timing Diagram A). Note that SOUT is triggered by negative
clock edges.
The E446 features a differential serial input and internal
divide-by-eight circuitry to facilitate the cascading of two
devices to build an 8:1 multiplexer. Figure 1 illustrates the
architecture for an 8:1 multiplexer using two E446s (see
Timing Diagram B). Notice the serial outputs (SOUT) of the
lower order converter feed the serial inputs of the higher
order device. This feed through of the serial inputs bounds
the upper end of the frequency of operation. The clock-to-
serial output propagation delay, plus the set-up time of the
serial input pins, must fit into a single clock period for the
cascade architecture to function properly. Using the worst
case values for these two parameters from the data sheet,
tPD CLK to SOUT = 1600ps and ts for SIN = –200ps, yields
a minimum period of 1400ps or a clock frequency of
700MHz.
The clock frequency is somewhat lower than that of a
single converter. In order to increase this frequency, it is
recommended that the clock edge feeding the E446A be
delayed with respect to the E446B, as shown in Figure 2.
Perhaps the easiest way to delay the second clock relative
to the first is to take advantage of the differential clock
inputs of the E446. By connecting the clock for E446A to
the complimentary clock input pin, the device will clock a
half a clock period after E446B (Figure 2). Utilizing this
simple technique will raise the potential conversion frequency
up to the maximum 1.3GHz of a stand-alone E446.
CLK
CLK
CLK
tPD
CLK to SOUT
E446B
SOUT
SOUT
E446A
SIN
SOUT
SIN
SOUT
SERIAL
DATA
D3 D2 D1 D0
D3 D2 D1 D0
D7 D6 D5 D4
D3 D2 D1 D0
PARALLEL DATA
1400ps
200ps
1600ps
Figure 1. Cascaded 8:1 Converter Architecture
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