INA206 datasheet(13/23 Pages) TI

13 / 23 page

INA206

INA207

INA208

SBOS360 − JULY 2006

www.ti.com

TRANSIENT PROTECTION

The −16V to +80V common-mode range of the INA206,

INA207, and INA208 is ideal for withstanding automotive

fault conditions ranging from 12V battery reversal up to

+80V

transients,

since

additional

protective

components are needed up to those levels. In the event

that the INA206, INA207, and INA208 are exposed to

transients on the inputs in excess of their ratings, then

external transient absorption with semiconductor transient

absorbers (zeners or Transzorbs) will be necessary. Use

of MOVs or VDRs is not recommended except when they

are used in addition to a semiconductor transient absorber.

Select the transient absorber such that it will never allow

the INA206, INA207, and INA208 to be exposed to

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

absorber tolerance, as well as additional voltage due to

transient absorber dynamic impedance). Despite the use

of internal zener-type ESD protection, the INA206,

INA207, and INA208 do not lend themselves to using

external resistors in series with the inputs since the internal

gain resistors can vary up to

±30%. (If gain accuracy is not

important, then resistors can be added in series with the

INA206, INA207, and INA208 inputs with two equal

resistors on each input.)

OUTPUT VOLTAGE RANGE

The output of the INA206, INA207, and INA208 is accurate

within the output voltage swing range set by the power

supply pin, V+. This performance is best illustrated when

using the INA208 (a gain of 100 version), where a 100mV

full-scale input from the shunt resistor requires an output

voltage swing of +10V, and a power-supply voltage

sufficient to achieve +10V on the output.

INPUT FILTERING

An obvious and straightforward location for filtering is at

the output of the INA206, INA207, and INA208 series;

however, this location negates the advantage of the low

output impedance of the internal buffer. The only other

option for filtering is at the input pins of the INA206,

INA207, and INA208, which is complicated by the internal

Ω + 30% input impedance; this is shown in Figure 5.

Using the lowest possible resistor values minimizes both

the initial shift in gain and effects of tolerance. The effect

on initial gain is given by Equation (3):

Gain Error%

+ 100 * 100

W ) R

FILT

Total effect on gain error can be calculated by replacing the

Ω term with 5kΩ − 30%, (or 3.5kΩ) or 5kΩ + 30% (or

6.5k

Ω). The tolerance extremes of RFILT can also be

inserted into the equation. If a pair of 100

Ω 1% resistors

are used on the inputs, the initial gain error will be 1.96%.

Worst-case tolerance conditions will always occur at the

lower excursion of the internal 5k

Ω resistor (3.5kΩ), and

the higher excursion of RFILT − 3% in this case.

Note that the specified accuracy of the INA206, INA207,

and INA208 must then be combined in addition to these

tolerances. While this discussion treated accuracy

worst-case conditions by combining the extremes of the

resistor values, it is appropriate to use geometric mean or

root sum square calculations to total the effects of

accuracy variations.

SHUNT << RFILTER

Ω

SUPPLY

Load

FILTER <100Ω

FILTER

1.2V REF OUT

CMP1 OUT

CMP2 OUT

CMP2 DELAY

CMP1 RESET

IN+

−

OUT

CMP1 IN−/0.6V REF

CMP1 IN+

CMP2 IN

−

CMP2 IN+/0.6V REF

GND

INA206

− INA208

SO−14, TSSOP−14

1.2V REF

f−3dB =

π(2R

FILTER)CFILTER

f−3dB

Figure 5. Input Filter (Gain Error − 1.5% to −2.2%)

(3)

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