8-Channel/4-Channel
Fault-Protected Analog Multiplexers
FEATURES
All switches off with power supply off
Analog output of on channel clamped within power
supplies if an overvoltage occurs
Latch-up proof construction
Low on resistance (270 Ω typical)
Fast switching times
t
ON
: 230 ns maximum
t
OFF
: 130 ns maximum
Low power dissipation (3.3 mW maximum)
Fault and overvoltage protection (−40 V to +55 V)
Break-before-make construction
TTL and CMOS compatible inputs
FUNCTIONAL BLOCK DIAGRAMS
ADG508F
S1
D
S8
1 OF 8
DECODER
00035-001
APPLICATIONS
Existing multiplexer applications (both fault-protected and
nonfault-protected)
New designs requiring multiplexer functions
A0 A1 A2 EN
Figure 1.
ADG509F
S1A
DA
S4A
GENERAL DESCRIPTION
The
and
are CMOS analog multi-
plexers, with the
comprising eight single channels
and the
comprising four differential channels. These
multiplexers provide fault protection. Using a series n-channel,
p-channel, n-channel MOSFET structure, both device and signal
source protection is provided in the event of an overvoltage or
power loss. The multiplexer can withstand continuous overvolt-
age inputs from −40 V to +55 V. During fault conditions with
power supplies off, the multiplexer input (or output) appears as
an open circuit and only a few nanoamperes of leakage current
will flow. This protects not only the multiplexer and the circuitry
driven by the multiplexer, but also protects the sensors or signal
sources that drive the multiplexer.
The
switches one of eight inputs to a common output
as determined by the 3-bit binary address lines A0, A1, and A2.
The
switches one of four differential inputs to a
common differential output as determined by the 2-bit binary
address lines A0 and A1. An EN input on each device is used
to enable or disable the device. When disabled, all channels are
switched off.
S1B
DB
S4B
1 OF 4
DECODER
00035-101
A0 A1 EN
Figure 2.
PRODUCT HIGHLIGHTS
1.
Fault protection. The
can withstand
continuous voltage inputs from −40 V to +55 V. When a
fault occurs due to the power supplies being turned off, all
the channels are turned off and only a leakage current of a
few nanoamperes flows.
On channel saturates while fault exists.
Low R
ON
.
Fast switching times.
Break-before-make switching. Switches are guaranteed
break-before-make so that input signals are protected
against momentary shorting.
Trench isolation eliminates latch-up. A dielectric trench
separates the p and n-channel MOSFETs thereby
preventing latch-up.
2.
3.
4.
5.
6.
Rev. F
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