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4 ±1A Single-Supply Low-Side Current Sensing Solution Reference Design TIDU675-June 2015
Copyright © 2015, Texas Instruments Incorporated
2.1 Error Analysis
There are two types of errors introduced by the circuit in Figure 2: offset and gain. To obtain more
information about these types of errors, please refer to TIPD129. Table 2 lists the error sources and their
respective type(s).
Table 2. Design Error Sources
U1A and R
1
-R
4
create a difference amplifier.
The ratios of R
2
/R
1
and R
4
/R
3
introduce a gain
error. The absolute value of the ratios
introduce a gain error and the matching of the
ratios determine the CMRR performance,
which translates to an offset error.
The accuracy of the voltage divider created by
R
5
and R
6
yields an offset error.
These errors ultimately combine and are measured at the output as gain and offset errors. It is common to
combine them using the root sum squared (RSS) method. This method is used when combining errors
with a normal distribution, thereby yielding typical total error. For a worst-case total error, simply add all
error terms directly.