a) Single-Pole Filter

b) Second-Order, Sallen-Key Filter

A1

A2

Single-Pole Filter

Capacitor

+2.7V to +18V

5kW

5kW

96kW

R

L

PRE OUT

BUF IN

GND

Output

IN-

IN+

V+

Load

Supply

R

S

INA271

A1

A2

Second-Order, Sallen-Key Filter Connection

+2.7V to +18V

C

FILT

C

FILT

5kW

5kW

96kW

R

L

PRE OUT

BUF IN

GND

Output

IN-

IN+

V+

Load

Supply

R

S

R

S

INA271

INA271-HT

SBOS521D – SEPTEMBER 2010 – REVISED AUGUST 2013

www.ti.com

TRANSIENT PROTECTION

resistors in series with the inputs since the internal

gain resistors can vary up to ±30%, but is tightly

The –16V to +80V common-mode range of the

matched (if gain accuracy is not important, then

INA271 is ideal for withstanding automotive fault

resistors can be added in series with the INA271

conditions ranging from 12V battery reversal up to

inputs with two equal resistors on each input).

+80V

transients,

since

no

additional

protective

components are needed up to those levels. In the

OUTPUT VOLTAGE RANGE

event that the INA271 is exposed to transients on the

inputs in excess of their ratings, external transient

The output of the INA271 is accurate within the

absorption with semiconductor transient absorbers

output voltage swing range set by the power-supply

(zeners or Transzorbs) will be necessary.

pin, V+.

Use of MOVs or VDRs is not recommended except

The INA271 readily enables the inclusion of filtering

when they are used in addition to a semiconductor

between the preamp output and buffer input. Single-

transient absorber. Select the transient absorber such

pole filtering can be accomplished with a single

that it will never allow the INA271 to be exposed to

capacitor because of the 96k

Ω output impedance at

transients greater than 80V (that is, allow for transient

PRE OUT on pin 3, as shown in Figure 17a.

absorber tolerance, as well as additional voltage

The INA271 readily lends itself to second-order

because of transient absorber dynamic impedance).

Sallen-Key configurations, as shown in Figure 17b.

Despite

the

use

of

internal

zener-type

ESD

When designing these configurations consider that

protection, the INA271 is not suited to using external

the PRE OUT 96k

Ω output impedance exhibits an

initial variation of ±30% with the addition of a

–2200ppm/°C temperature coefficient.

Figure 17. The INA271 can be easily connected for first- or second-order filtering. Remember to use the

appropriate buffer gain of 2 when designing Sallen-Key configurations.

10

Submit Documentation Feedback

Copyright © 2010–2013, Texas Instruments Incorporated

Product Folder Links: INA271-HT