Multiplexer Configuration; Introduction; Basic Multiplexer Configurations - Keithley 7021 Instruction Manual

Multiplexer Configuration

Introduction

This section covers the basics for multiplexer switching and
is arranged as follows:
• Basic multiplexer configurations — Covers the basic
multiplexer configurations: dual 1 × 12 and 1 × 18 con-
figuration and single 1 × 30 configuration. The signifi-
cance of the backplane jumpers is also covered here.
Typical multiplex switching schemes — Explains some
•
of the basic ways a multiplexer can be used to source or
measure. Covers single-ended switching, differential
(floating) switching, sensing, and SMU connections.
Multiplexer expansion — Discusses the various config-
•
urations that are possible by using multiple cards.
Switching Topology
for all Channels
Figure 2-1
Model 7021 simplified schematic
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1 6 11 16 21 26
2 7 12 17 22 27
Bank A
3 8 13 18 23 28
4 9 14 19 24 29
Bank B
5 10 15 20 25 30
Input (1 of 30)
HI LO
HI
Bank
LO
Basic multiplexer configurations
A simplified schematic of the Model 7021 multiplex banks is
shown in Figure 2-1. It is organized as two multiplex banks:
1 × 12 and 1 × 18. Bank A has 12 inputs and one output, and
bank B has 18 inputs and one output. Two-pole switching is
provided for each multiplexer input, with HI and LO
switched. The two banks can be jumpered together to expand
multiplexer inputs, and backplane jumpers provide bank
connections to an adjacent card installed in a Model 7001/
7002 mainframe.
HI
A
LO
Bank-to-Bank
Jumpers
HI
Jumpers
B
LO
HI HI
LO LO
Backplane Jumpers
(to 7001/7002
Analog Backplane)
Note: Factory configuration shown.
2
2-1