Datasheet

a)Single-PoleFilter b)Second-Order,Sallen-KeyFilter
A1
A2
Single-PoleFilter
Capacitor
+2.7Vto+18V
5kW5kW
96kW
R
L
PREOUT BUFIN
GND
Output
IN-IN+ V+
Load
Supply
R
S
INA270
A1
A2
Second-Order,Sallen-KeyFilterConnection
+2.7Vto+18V
C
FILT
C
FILT
5kW5kW
96kW
R
L
PREOUT BUFIN
GND
Output
IN-IN+ V+
Load
Supply
R
S
R
S
INA270
INA270
INA271
www.ti.com SBOS381C –FEBRUARY 2007–REVISED MAY 2010
TRANSIENT PROTECTION inputs since the internal gain resistors can vary up to
±30%, but are tightly matched (if gain accuracy is not
The –16V to +80V common-mode range of the
important, then resistors can be added in series with
INA270 and INA271 is ideal for withstanding
the INA270 and INA271 inputs with two equal
automotive fault conditions ranging from 12V battery
resistors on each input).
reversal up to +80V transients, since no additional
protective components are needed up to those levels.
OUTPUT VOLTAGE RANGE
In the event that the INA270 and INA271 are exposed
to transients on the inputs in excess of their ratings,
The output of the INA270 and INA271 is accurate
external transient absorption with semiconductor
within the output voltage swing range set by the
transient absorbers (zeners or Transzorbs) will be
power-supply pin, V+.
necessary.
The INA270 and INA271 readily enable the inclusion
Use of MOVs or VDRs is not recommended except
of filtering between the preamp output and buffer
when they are used in addition to a semiconductor
input. Single-pole filtering can be accomplished with a
transient absorber. Select the transient absorber such
single capacitor because of the 96kΩ output
that it will never allow the INA270 and INA271 to be
impedance at PRE OUT on pin 3, as shown in
exposed to transients greater than 80V (that is, allow
Figure 16a.
for transient absorber tolerance, as well as additional
The INA270 and INA271 readily lend themselves to
voltage because of transient absorber dynamic
second-order Sallen-Key configurations, as shown in
impedance). Despite the use of internal zener-type
Figure 16b. When designing these configurations
ESD protection, the INA270 and INA271 are not
consider that the PRE OUT 96kΩ output impedance
suited to using external resistors in series with the
exhibits an initial variation of ±30% with the addition
of a –2200ppm/°C temperature coefficient.
Figure 16. The INA270–INA271 can be easily connected for first- or second-order filtering. Remember to
use the appropriate buffer gain (INA270 = 1.4, INA271 = 2) when designing Sallen-Key configurations.
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