DG458_08 Datasheet, PDF (9/10 Pages) Vishay Siliconix – Fault-Protected Single 8-Ch/Differential 4-Ch Analog Multiplexers

DETAILED DESCRIPTION
The Vishay Siliconix DG458 and DG459 multiplexers are
fully fault- and overvoltage-protected for continuous input
voltages up to ± 35 V whether or not voltage is applied to the
power supply pins (V+, V-). These multiplexers are built on a
high-voltage junction-isolated silicon-gate CMOS process.
Two n-channel and one p-channel MOSFETs are connected
in series to form each channel (Figure 1).
Within the normal analog signal range (± 10 V), the r_DS(on)
variation as a function of analog signal voltage is comparable
to that of the classic parallel N-MOS and P-MOS switches.
When the analog signal approaches or exceeds either
supply rail, even for an on-channel, one of the three series
MOSFETs gets cut-off, providing inherent protection against
overvoltages even if the multiplexer power supply voltages
are lost. This protection is good up to the breakdown voltage
of the respective series MOSFETs. Under fault conditions
only sub microamp leakage currents can flow in or out of the
multiplexer. This not only provides protection for the
multiplexer and succeeding circuitry, but it allows normal,
undisturbed operation of all other channels. Additionally, in
case of power loss to the multiplexer, the loading caused on
the transducers and signal sources is insignificant, therefore
redundant multiplexers can be used on critical applications
such as telemetry and avionics.
DG458/459
Vishay Siliconix
- 35 V
Overvoltage _S
Q₁ - 35 V
DS
Q₂
DS
Q₃
+ 35 V
D ^Overvoltage
n-Channel
n-Channel
G
G
G
MOSFET
MOSFET
is Off
is On
p-Channel
MOSFET
is Off
(a) Overvoltage with Multiplexer Power Off
- 15 V
+ 15 V
- 15 V
- 35 V
Overvoltage
Q₁
Q₂
Q_{3 + 35 V}
Overvoltage
n-Channel
MOSFET
is On
- 15 V
+ 15 V
n-Channel
MOSFET
is Off
p-Channel
MOSFET
is Off
(b) Overvoltage with Multiplexer Power On
Figure 5. Overvoltage Protection
Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon
Technology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and
reliability data, see http://www.vishay.com/ppg?70064.
Document Number: 70064
S-71155–Rev. G, 11-Jun-07
www.vishay.com
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