AD8226ARMZ-R7 datasheet(22/29 Pages) AD

22 / 29 page

Data Sheet

AD8226

Rev. C | Page 21 of 28

Common-Mode Rejection Ratio Over Frequency

Poor layout can cause some of the common-mode signals to be

converted to differential signals before reaching the in-amp.

Such conversions occur when one input path has a frequency

response that is different from the other. To keep CMRR across

frequency high, the input source impedance and capacitance of

each path should be closely matched. Additional source resistance

in the input path (for example, for input protection) should be

placed close to the in-amp inputs, which minimizes their

interaction with parasitic capacitance from the PCB traces.

Parasitic capacitance at the gain-setting pins can also affect

CMRR over frequency. If the board design has a component

at the gain-setting pins (for example, a switch or jumper), the

part should be chosen so that the parasitic capacitance is as

small as possible.

Power Supplies

A stable dc voltage should be used to power the instrumentation

amplifier. Note that noise on the supply pins can adversely affect

performance. For more information, see the PSRR performance

curves in Figure 23 and Figure 24.

A 0.1 μF capacitor should be placed as close as possible to each

supply pin. As shown in Figure 61, a 10 μF tantalum capacitor

can be used farther away from the part. In most cases, it can be

shared by other precision integrated circuits.

AD8226

+VS

+IN

–IN

LOAD

REF

0.1µF

10µF

0.1µF

10µF

–VS

VOUT

Figure 61. Supply Decoupling, REF, and Output Referred to Local Ground

References

The output voltage of the AD8226 is developed with respect to

the potential on the reference terminal. Care should be taken to

tie REF to the appropriate local ground.

INPUT BIAS CURRENT RETURN PATH

The input bias current of the AD8226 must have a return path

to ground. When the source, such as a thermocouple, cannot

provide a return current path, one should be created, as shown

in Figure 62.

THERMOCOUPLE

+VS

REF

–VS

AD8226

CAPACITIVELY COUPLED

+VS

REF

–VS

AD8226

TRANSFORMER

+VS

REF

–VS

AD8226

INCORRECT

CAPACITIVELY COUPLED

+VS

REF

–VS

AD8226

fHIGH-PASS = 2πRC

THERMOCOUPLE

+VS

REF

–VS

10MΩ

AD8226

TRANSFORMER

+VS

REF

–VS

AD8226

CORRECT

Figure 62. Creating an IBIAS Path

AD8226ARMZ-R7 数据表(PDF) 22 Page - Analog Devices

AD8226ARMZ-R7 数据表(HTML) 22 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

数据表下载

链接网址

AD8226ARMZ-R7 数据表(PDF) 22 Page - Analog Devices

AD8226ARMZ-R7 数据表(HTML) 22 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

数据表 下载

链接网址

数据表下载