INSTALLATION AND
OPERATING INSTRUCTIONS
The ENABLE input, pin 2, 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 2-bit (MPC509A) or 3-bit (MPC508A) Channel 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
In 1
In 2
In 3
Out
8
2
MPC508A
En
+V
In 8
A0 A1 A2
Multiplexer
Output
In 1
MPC508A
Out
Direct
En
+V
In 8
A0 A1 A2
tie it to +VSUPPLY
.
In 1
In 2
In 3
Buffered
OPA602
1/4 OPA404
If the +15V and/or –15V supply voltage is absent or shorted
to ground, the MPC509A and MPC508A multiplexers will
not be damaged; however, some signal feedthrough to the
output will occur. Total package power dissipation must not
be exceeded.
Out
8
2
MPC508A
En
+V
In 8
A0 A1 A2
For best settling speed, the input wiring and interconnections
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
4LSBs 4MSBs
6-Bit Channel
Address Generator
Settling Time to
±0.01% is 20µs
with RS = 100Ω
To preserve common-mode rejection of the MPC509A, 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 com-
mon-mode guard driver.
FIGURE 6. Channel Expansion Up to 64 Channels Using
8 x 8 Two-Tiered Expansion.
Differential Multiplexer (MPC509A)
Single or multitiered configurations can be used to expand
multiplexer channel capacity up to 32 channels using a
32 x 1 or 16 channels using a 4 x 4 configuration.
CHANNEL EXPANSION
Single-Ended Multiplexer (MPC508A)
Single-Node Expansion
Up to 32 channels (four multiplexers) can be connected to a
single node, or up to 64 channels using nine MPC508A
multiplexers on a two-tiered structure as shown in Figures 5
and 6.
The 32 x 1 configuration is simply eight (MPC509A) units
tied to a single node. Programming is accomplished with a
5-bit counter, using the 2LSBs of the counter to control
Channel Address inputs A0 and A1 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 2) of the MPC509A
multiplexers.
In 1
In 2
In 3
Out
MPC
508A
8
2
Group 1
Ch1-8
Group 1
Enable
Multiplexer
Output
In 8
Two-Tier Expansion
A2 A1 A0
Direct
Using a 4 x 4 two-tier structure for expansion to 16 channels,
the programming is simplified. A 4-bit counter output does
not require a 1-of-8 decoder. The 2LSBs of the counter drive
the A0 and A1 inputs of the four first-tier multiplexers and the
2MSBs of the counter are applied to the A0 and A1 inputs of
the second-tier multiplexer.
5-Bit
Binary
Counter
To
Group
2
20
21
22
Buffered
OPA602
1/4 OPA404
23
24
Single vs Multitiered Channel Expansion
A2 A1 A0
To
Group
3
In 1
In 2
In 3
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 in the ON condition (short). Should a
channel fail ON in the single-node configuration, data cannot
be taken from any channel, whereas only one channel group
is failed (4 or 8) in the multitiered configuration.
Group 4
Enable
Out
2
MPC
508A
8
In 8
Group 4
Ch25-42
Settling Time to 0.01% for RS < 100Ω
—Two MPC508A units in parallels: 10µs
—Four MPC509 A units in parallels: 12µs
FIGURE 5. 32-Channel, Single-Tier Expansion.
MPC508A, MPC509A
11
SBFS019A
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