Differential Multiplexer (MPC507A)
INSTALLATION AND
OPERATING INSTRUCTIONS
Single or multitiered configurations can be used to expand
multiplexer channel capacity up to 64 channels using a
64 x 1 or an 8 x 8 configuration.
The ENABLE input, pin 18, is included for expansion of
the number of channels on a single node as illustrated in
Figure 5. With ENABLE line at a logic 1, the channel is
selected by the 3-bit (MPC507A or 4-bit MPC506A) Chan-
nel Select Address (shown in the Truth Tables). If ENABLE
is at logic 0, all channels are turned OFF, even if the Channel
Address Lines are active. If the ENABLE line is not to be
used, simply tie it to +V supply.
Single-Node Expansion
The 64 x 1 configuration is simply eight (MPC507A) units
tied to a single node. Programming is accomplished with a
6-bit counter, using the 3LSBs of the counter to control
Channel Address inputs A0, A1, A2 and the 3MSBs of the
counter to drive a 1-of-8 decoder. The 1-of-8 decoder then
is used to drive the ENABLE inputs (pin 18) of the MPC507A
multiplexers.
If the +15V and/or –15V supply voltage is absent or shorted
to ground, the MPC507A and MPC506A multiplexers will
not be damaged; however, some signal feedthrough to the
output will occur. Total package power dissipation must not
be exceeded.
Two-Tier Expansion
Using an 8 x 8 two-tier structure for expansion to 64
channels, the programming is simplified. The 6-bit counter
output does not require a 1-of-8 decoder. The 3LSBs of the
counter drive the A0, A1 and A2 inputs of the eight first-tier
multiplexers and the 3MSBs of the counter are applied to the
A0, A1, and A2 inputs of the second-tier multiplexer.
For best settling speed, the input wiring and interconnec-
tions between multiplexer output and driven devices should
be kept as short as possible. When driving the digital inputs
from TTL, open collector output with pull up resistors are
recommended (see Typical Performance Curves, Access
Time).
Single vs Multitiered Channel Expansion
To preserve common-mode rejection of the MPC507A, use
twisted-shielded pair wire for signal lines and inter-tier
connections and/or multiplexer output lines. This will help
common-mode capacitance balance and reduce stray signal
pickup. If shields are used, all shields should be connected
as close as possible to system analog common or to the
common-mode guard driver.
In addition to reducing programming complexity, two-tier
configuration offers the added advantages over single-node
expansion of reduced OFF channel current leakage (reduced
OFFSET), better CMR, and a more reliable configuration if
a channel should fail ON in the single-node configuration,
data cannot be taken from any channel, whereas only one
channel group is failed (8 or 16) in the multitiered configu-
ration.
In 1
MPC
506A
In 2
In 3
Out
28
Group 1
Ch1-16
In 1
In 2
In 3
Group 1
Enable
Out
Multiplexer
Output
In 16
18
28
A3 A2 A1 A0
MPC506A
Direct
6-Bit
To
Group
2
En
+V
In 16
18
Binary
Counter
20
Multiplexer
Output
21
22
23
24
25
A0 A1 A2 A3
Out
Direct
In 1
28
Buffered
OPA602
1/4 OPA404
MPC506A
En
+V
18
In 16
A3 A2 A1 A0
To
Group
3
A0 A1 A2 A3
In 1
In 2
In 3
Group 4
Enable
Out
Buffered
OPA602
1/4 OPA404
Out
18
18
MPC506A
Group 4
MPC506A
En
+V
28
49-64
28
In 16
Settling time to 0.01% for RS 100Ω
—Two MPC506A units in parallel 10µs
—Four MPC507A units in parallel 12µs
A0 A1 A2 A3
FIGURE 5. 64-Channel, Single-Tier Expansion.
CHANNEL EXPANSION
4LSBs
4MSBs
Settling Time to
8-Bit Channel
Address Generator
Single-Ended Multiplexer (MPC506A)
0.01% is 20µs
with RS = 100Ω
Up to 64 channels (four multiplexers) can be connected to a
single node, or up to 256 channels using 17 MPC506A
multiplexers on a two-tiered structure as shown in Figures 5
and 6.
FIGURE 6. Channel Expansion up to 256 Channels Using
16x16 Two-Tiered Expansion
MPC506A, MPC507A
11
SBFS018A
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