Datasheet

10 V/divm
Number of Conversions
0 200 400 600 800 1000
Conversion Time: 140 sm
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 140μs 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 588μs 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 588μs,
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
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