AN4439 Datasheet, PDF (1/16 Pages) STMicroelectronics – L99ASC03 current sense amplifier offset adjust

AN4439
Application note
L99ASC03 current sense amplifier offset adjust
Introduction
The L99ASC03 is a 3 phase BLDC motor controller. This device drives 6 MOSFETs for
standard trapezoidal driven BLDC motors using back EMF for rotor position detection. This
device has a current sense amplifier that provides an output of 1/2 Vcc (2.5 V) when there is
no current sensed. This was done to provide bi-directional current detection. Some
applications only need unidirectional current sensing. When this is the case, reducing or
eliminating this offset would be advantageous to allow full use of the available
microcontroller ADC range.
This application note provides the detailed calculations to provide the proper external
resistor selection and tolerances required for optimal current sensing accuracy.
March 2014
DocID025908 Rev 1
1/16
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