8

®

MPC801

CHANNEL EXPANSION

Single-Tier Expansion

Up to eight MPC801s can be connected to a single node to

form a 64-channel single-ended multiplexer, or up to eight

MPC801s can be connected to two nodes to form a

32-channel differential multiplexer. Programming is

accomplished with a 6-bit address and a 1-of-8 decoder (see

Figure 5). The decoder drives the enable inputs of the

MPC801 turning on only one multiplexer at a time.

Two-Tier Expansion

Up to nine MPC801s can be connected in a two-tier structure

to form a 64-channel single-ended multiplexer (see Figure

6), or up to five MPC801s can be connected in a two-tier

structure to form a 16-channel differential multiplexer. Pro-

gramming is accomplished with a 6-bit address.

SINGLE VS MULTITIERED CHANNEL EXPANSION

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 can-

not be taken from any channel, whereas only one-channel

group is failed (4 or 8) in the multitiered configuration.

Enable

Out A

Out B

In8

In1

In2

In3

A

MPC801

Enable

Out A

Out B

In8

In1

In2

In3

A

MPC801

6-Bit Channel

Address Generator

1 of 8

Decoder

Multiplexer

Output

To multiplexers 3 - 8

FIGURE 5. 64-channel, Single-tier, Single-ended Expansion.

Enable

Out A

Out B

In8

In1

In2

In3

A

MPC801

Enable

Out A

Out B

In8

In1

In2

In3

A

MPC801

6-Bit Channel

Address Generator

To multiplexers 3 - 8

Enable

Out A

Out B

In8

In1

In2

In3

A

MPC801

Multiplexer

Output

FIGURE 6. 64-channel, Two-tier, Single-ended Expansion.