ADG508FBRWZ Analog Devices Inc, ADG508FBRWZ Datasheet - Page 11

• Manufacturer Part Number: ADG508FBRWZ
• Description: IC MULTIPLEXER 8X1 16SOIC
• Manufacturer: Analog Devices Inc
• Type: Analog Multiplexerr

Specifications of ADG508FBRWZ

• Function: Multiplexer
• Circuit: 1 x 8:1
• On-state Resistance: 300 Ohm
• Voltage Supply Source: Dual Supply
• Voltage - Supply, Single/dual (±): ±10.8 V ~ 16.5 V
• Current - Supply: 20µA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.50mm Width)
• No. Of Circuits: 1
• Supply Current: 600µA
• On State Resistance Max: 300ohm
• Supply Voltage Range: 10.8V To 16.5V
• Operating Temperature Range: -40°C To +85°C
• Analog Switch Case Style: SOIC
• Package: 16SOIC W
• Maximum On Resistance: 350@±15V Ohm
• Maximum Propagation Delay Bus To Bus: 300@±15V ns
• Maximum High Level Output Current: 20 mA
• Multiplexer Architecture: 8:1
• Maximum Turn-on Time: 250@±15V ns
• Power Supply Type: Dual
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

THEORY OF OPERATION
The ADG508F/ADG509F/ADG528F multiplexers are capable of
withstanding overvoltages from −40 V to +55 V, irrespective of
whether the power supplies are present or not. Each channel of
the multiplexer consists of an n-channel MOSFET, a p-channel
MOSFET, and an n-channel MOSFET, connected in series. When
the analog input exceeds the power supplies, one of the MOSFETs
will switch off, limiting the current to submicroamp levels, thereby
preventing the overvoltage from damaging any circuitry following
the multiplexer. Figure 17 illustrates the channel architecture that
enables these multiplexers to withstand continuous overvoltages.
When an analog input of V
the ADG508F/ADG509F/ADG528F, the multiplexer behaves as
a standard multiplexer, with specifications similar to a standard
multiplexer, for example, the on-resistance is 400 Ω maximum.
However, when an overvoltage is applied to the device, one of
the three MOSFETs will turn off.
Figure 17 to Figure 20 show the conditions of the three MOSFETs
for the various overvoltage situations. When the analog input
applied to an ON channel approaches the positive power supply
line, the n-channel MOSFET turns OFF since the voltage on
the analog input exceeds the difference between V
n-channel threshold voltage (V
tive than V
MOSFET will turn off since the analog input is more negative
than the difference between V
voltage (V
3 V, the analog input range to the multiplexer is limited to
−12 V to +13.5 V when a ±15 V power supply is used.
When the power supplies are present but the channel is off,
again either the p-channel MOSFET or one of the n-channel
MOSFETs will turn off when an overvoltage occurs.
Finally, when the power supplies are off, the gate of each
MOSFET will be at ground. A negative overvoltage switches
on the first n-channel MOSFET but the bias produced by the
overvoltage causes the p-channel MOSFET to remain turned
off. With a positive overvoltage, the first MOSFET in the series
will remain off since the gate to source voltage applied to this
MOSFET is negative.
TP
SS
). Since V
is applied to the multiplexer, the p-channel
TN
is nominally 1.5 V and V
SS
+ 3 V to V
SS
TN
and the p-channel threshold
). When a voltage more nega-
DD
− 1.5 V is applied to
TP
DD
is typically
and the
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During fault conditions, the leakage current into and out of the
ADG508F/ADG509F/ADG528F is limited to a few microamps.
This protects the multiplexer and succeeding circuitry from
over stresses as well as protecting the signal sources which drive
the multiplexer. Also, the other channels of the multiplexer will
be undisturbed by the overvoltage and will continue to operate
normally.
OVERVOLTAGE
OVERVOLTAGE
OVERVOLTAGE
OVERVOLTAGE
Figure 17. +55 V Overvoltage Input to the On Channel
Figure 18. −40 V Overvoltage on an Off Channel with
Figure 19. +55 V Overvoltage with Power Off
Figure 20. −40 V Overvoltage with Power Off
n-CHANNEL
n-CHANNEL
n-CHANNEL
n-CHANNEL
MOSFET IS
MOSFET IS
MOSFET IS
MOSFET IS
+55V
–40V
+55V
–40V
ADG508F/ADG509F/ADG528F
OFF
OFF
ON
ON
Multiplexer Power On
V
V
DD
SS
Q1
Q1
Q1
Q1
V
V
SS
DD
p-CHANNEL
p-CHANNEL
MOSFET IS
MOSFET IS
Q2
Q2
Q2
Q2
OFF
OFF
Q3
Q3
Q3
Q3