Number of Conversions

0

200

400

600

800

1000

Conversion Time: 140 s

m

Conversion Time: 1.1ms

Conversion Time: 8.244ms

INA226

www.ti.com

SBOS547

– JUNE 2011

Averaging and Conversion Time Considerations

The INA226 has programmable conversion times for both the shunt voltage and bus voltage measurements. The

conversion times for these measurements can be selected from as fast as 140

μs to as long as 8.244ms. The

conversion time settings, along with the programmable averaging mode, allow the INA226 to be configured to

optimize the available timing requirements in a given application. For example, if a system requires that data be

read every 5ms, the INA226 could be configured with the conversion times set to 588

μs and the averaging mode

set to 4. This configuration results in the data updating approximately every 4.7ms. The INA226 could also be

configured with a different conversion time setting for the shunt and bus voltage measurements. This type of

approach is common in applications where the bus voltage tends to be relatively stable. This situation can allow

for the time focused on the bus voltage measurement to be reduced relative to the shunt voltage measurement.

The shunt voltage conversion time could be set to 4.156ms with the bus voltage conversion time set to 588

μs,

with the averaging mode set to 1. This configuration also results in data updating approximately every 4.7ms.

There are trade-offs associated with the settings for conversion time and the averaging mode used. The

averaging feature can significantly improve the measurement accuracy by effectively filtering the signal. This

approach allows the INA226 to reduce any noise in the measurement that may be caused by noise coupling into

the signal. A greater number of averages enables the INA226 to be more effective in reducing the noise

component of the measurement.

The conversion times selected can also have an impact on the measurement accuracy. This effect can seen in

Figure 21. Multiple conversion times are shown here to illustrate the impact of noise on the measurement. In

order to achieve the highest accuracy measurement possible, a combination of the longest allowable conversion

times and highest number of averages should be used, based on the timing requirements of the system.

Figure 21. Noise vs Conversion Time

Copyright

© 2011, Texas Instruments Incorporated

Submit Documentation Feedback

11

Product Folder Link(s): INA226