Fault and Overvoltage Protection up to ؎40␣ V
Signal Paths Open Circuit with Power Off
Signal Path Resistance of RON with Power On
44 V Supply Maximum Ratings
Low On Resistance 80 ⍀ Typ
1 nA Max Path Current Leakage @ +25؇C
Low Power Dissipation 0.8␣ W Typ
Sensitive Measurement Equipment
Hot-Insertion Rack Systems
ADC Input Channel Protection
Single Channel Protector
in an SOT-23 Package
FUNCTIONAL BLOCK DIAGRAM
@ VDD – 1.5V
The ADG465 is a single channel protector in an SOT-23 pack-
age. The channel protector is placed in series with the signal
path, and will protect sensitive components from voltage tran-
sience in the signal path whether or not the power supplies are
present. Because the channel protection works regardless of the
presence of the supplies, the channel protectors are ideal for use
in applications where correct power sequencing cannot always
be guaranteed to protect analog inputs (e.g., hot-insertion rack
systems). This is discussed further, and some example circuits
are given, in the Applications section of this data sheet.
A channel protector consists of an n-channel MOSFET, a
p-channel MOSFET and an n-channel MOSFET, connected in
series. The channel protector behaves like a series resistor dur-
ing normal operation, i.e., (VSS + 2 V) < VIN < (VDD – 1.5 V).
When a channel’s analog input exceeds the power supplies
(including VDD and VSS = 0 V), one of the MOSFETs will
switch off, clamping the output to either VSS + 2 V or VDD – 1.5 V.
Circuitry and signal source protection is provided in the event of
an overvoltage or power loss. The channel protectors can with-
stand overvoltage inputs from –40 V to +40 V. See the Circuit
Information section of this data sheet.
The ADG465 can operate from both bipolar and unipolar
supplies. The channels are normally on when power is con-
nected, and open circuit when power is disconnected. With
power supplies of ± 15 V, the on-resistance of the ADG465 is
80 Ω typ, with a leakage current of ± 1 nA max. When power
is disconnected, the input leakage current is approximately
± 5 nA typ.
The ADG465 is available in a 6-lead plastic surface mount
SOT-23 package, and an 8-lead µSOIC package.
1. Fault Protection.
The ADG465 can withstand continuous voltage inputs from
–40 V to +40 V. When a fault occurs due to the power sup-
plies being turned off, or due to an overvoltage being applied
to the ADG465, the output is clamped. When power is turned
off, current is limited to the nanoampere level.
2. Low Power Dissipation.
3. Low RON 80 Ω typ.
4. Trench Isolation Latchup-Proof Construction.
A dielectric trench separates the p- and n-channel MOSFETs
thereby preventing latchup.
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 1998