ADG467BRZ-REEL7 Analog Devices Inc, ADG467BRZ-REEL7 Datasheet - Page 9

• Manufacturer Part Number: ADG467BRZ-REEL7
• Description: IC,Transient-Protection Circuit,CMOS,SOP,18PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Series: ADG467r

Specifications of ADG467BRZ-REEL7

• Voltage - Clamping: ±40V
• Technology: Mixed Technology
• Number Of Circuits: 8
• Applications: General Purpose
• Package / Case: 18-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power (watts): -
• Voltage - Working: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
Overvoltage and Power Supply Sequencing Protection
The ADG466 and ADG467 are ideal for use in applications
where input overvoltage protection is required and correct
power supply sequencing cannot always be guaranteed. The
overvoltage protection ensures that the output voltage of the
channel protector will not exceed the threshold voltages set by
the supplies (see Circuit Information) when there is an overvolt-
age on the input. When the input voltage does not exceed these
threshold voltages, the channel protector behaves like a series
resistor (60
vary slightly with operating conditions (see Typical Performance
Graphs).
The power sequencing protection is afforded by the fact that
when the supplies to the channel protector are not connected,
the channel protector becomes a high resistance device. Under
this condition all transistors in the channel protector are off and
the only currents that flow are leakage currents, which are at the
Figure 23 shows a typical application that requires overvoltage
and power supply sequencing protection. The application shows
a Hot-Insertion rack system. This involves plugging a circuit
board or module into a live rack via an edge connector. In this
type of application it is not possible to guarantee correct power
supply sequencing. Correct power supply sequencing means
that the power supplies should be connected before any external
signals. Incorrect power sequencing can cause a CMOS device
to “latch up.” This is true of most CMOS devices regardless of
the functionality. RC networks are used on the supplies of the
channel protector (Figure 23) to ensure that the rest of the
circuitry is powered up before the channel protectors. In this
way, the outputs of the channel protectors are clamped well
below V
ensure that the supplies on the channel protector never exceed
the supply rails of the board when it is being disconnected.
REV. A
A level.
Figure 23. Overvoltage and Power Supply Sequencing
Protection
–2.5V TO +2.5V
ANALOG IN
DD
LOGIC
LOGIC
GND
and V
+5V
–5V
typ). The resistance of the channel protector does
CONNECTOR
SS
EDGE
until the capacitors are charged. The diodes
ADG466
V
DD
V
SS
CONTROL
LOGIC
ADC
–9–
Again this ensures that signals on the inputs of the CMOS de-
vices never exceed the supplies.
High Voltage Surge Suppression
The ADG466 and ADG467 are not intended for use in high
voltage applications like surge suppression. The ADG466
and ADG467 have breakdown voltages of V
V
nected. When the power supplies are disconnected, the break-
down voltages on the input of the channel protector are 35 V.
In applications where inputs are likely to be subject to overvolt-
ages exceeding the breakdown voltages quoted for the channel
protectors, transient voltage suppressors (TVSs) should be used.
These devices are commonly used to protect vulnerable circuits
from electric overstress such as that caused by electrostatic
discharge, inductive load switching and induced lightning. How-
ever, TVSs can have a substantial standby (leakage) current
(300 A typ) at the reverse standoff voltage. The reverse standoff
voltage of a TVS is the normal peak operating voltage of the
circuit. Also TVS offer no protection against latch-up of sensitive
CMOS devices when the power supplies are off. The best solution
is to use a channel protector in conjunction with a TVS to provide
the best leakage current specification and circuit protection.
Figure 24 shows an input protection scheme that uses both a
TVS and channel protector. The TVS is selected with a reverse
standoff voltage that is much greater than operating voltage of
the circuit (TVSs with higher breakdown voltages tend to have
better standby leakage current specifications) but is inside the
breakdown voltage of the channel protector. This circuit pro-
tects the circuitry whether the power supplies are present
or not.
DD
+ 20 V on the inputs when the power supplies are con-
Figure 24. High Voltage Protection
V
DD
= +5V
TVSs
BREAKDOWN
VOLTAGE = 20V
ADG466
ADG466/ADG467
V
SS
= –5V
SS
– 20 V and
ADC