AN836 Datasheet, PDF (1/6 Pages) STMicroelectronics – LOW FORWARD VOLTAGE SCHOTTKY DIODE

AN836
Current Sense Amplifier Performance Comparison:
TS1100 vs. Maxim MAX9634
1. Introduction
Overall measurement accuracy in current-sense amplifiers is a function of both gain error and amplifier input offset
voltage performance. Of the two error sources, amplifier input offset voltage can impact the design more so than
gain error. If the sense resistor needs to be small to maximize power to the load and to minimize power dissipation;
then amplifier input offset voltage becomes the dominant error term. To minimize load current sense error, a
current-sense amplifier with a lower input offset voltage is required. By comparing the TS1100 against the
MAX9634 side-by-side, the TS1100’s 3-to-1 improvement in amplifier input offset voltage translates into a 2x
improvement in current measurement accuracy.
2. Overview
As shown in Table 1, the TS1100 family of current sense amplifiers provides an input offset voltage of only 30 µV
with a gain option of 25, 50, 100, and 200. When compared to the MAX9634, the TS1100 exhibits a factor of three
lower input offset voltage.
Table 1. TS1100 and MAX9634 Data Sheet Specifications
TS1100
TS1100
Gain Error (%)
Gain Options
MAX9634
±30 (typ)
±0.1%
25
50
100
200
±100 (typ)
±0.1%
25
50
100
200
The output voltage is a function of the gain and VSENSE. However, due to a finite gain error and input offset
voltage, VOS, the total output voltage is a function of the gain error, VSENSE, and VOS. This is shown in
Equations 1 and 2 below.
V_OUT(ideal) = Gain  V_SENSE
Equation 1.
V_OUT(actual) = Gain  V_SENSE + Gain  Gain error  V_SENSE  V_OS
Equation 2.
Rev. 1.0 1/15
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AN836