EDGE HIGH-PERFORMANCE PRODUCTS
Circuit Description (continued)
The Edge142 offers a 4 X 2 cross point switch in which
one of four input signals are selected to two independent
outputs. Each output signal’s propagation delay and
pulse width may then be adjusted via external control.
Both the output and multiplexer output signals may be
enabled or disabled, as documented below.
EN* OUT/OUT* MUX EN MUX(0,1)OUT
The truth table below documents the multiplexer
functionality. Notice that there are no restrictions
between the selection of channel 0 and channel 1.
Propagation Delay Adjust
SEL01 SEL00 OUT0 SEL11 SEL10 OUT1
0 IN0 0
1 IN1 0
The Edge142 supports two independent delay functions,
which are described in the table below.
0 IN2 1
1 IN3 1
The Edge142 provides MUX OUT0 / MUX OUT0* and
MUX OUT1 / MUX OUT1*, additional buffered differential
output signals. These signals are selected from OUT0
or OUT1, depending on the state of MUX SEL, as indicated
in the table below.
MUX(0,1) SEL MUXOUT0
0 OUT0 / OUT0* OUT1 / OUT1*
VFALL 0 ps 300 ps
VDELAY controls the propagation delay of both the rising
and falling edge (see Figure 2). An input signal is
selected and then delayed by some programmable
amount (Tspan) determined by the analog input VDELAY.
The rising and falling edges are delayed equally. The
propagation delay for a rising and a falling edge is defined
Tpd+, Tpd- = Tpd(nom) + Tspan
1 OUT1 / OUT1* OUT0 / OUT0*
The MUX OUT signals allow either of the delayed outputs
to be sent to an alternative destination without having
to daisy chain the outputs to multiple destinations. This
feature permits point to point routing of all critical timing
signals in an effort to maintain the cleanest transmission
lines for these signals.
The MUX OUT signals also provide a method for sending
one common selected input signal to two independent
destinations. This feature is useful when fanning out
driver data and driver enable signals to multiple test
where Tpd(nom) is the propagation delay of the part
with zero programmed delay, and Tspan is the additional
delay programmed via the VDELAY input. Notice that
Tspan can be either positive or negative, depending on
the nominal biasing of VDELAY, thus allowing bidirectional
propagation delay adjustment. The transfer function
for Tspan vs. VDELAY is shown in Figure 4.
(VDELAY = +0.1V)
(VDELAY = –1.3V)
2000 Semtech Corp.
Figure 2. VDELAY Control