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AS1545

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

On top of the difference calculator, the ADC also provide us with information regarding input signals in quadrature (90

degrees phase difference) like the ones we would get from a position calculation system of a motor control.

In order for this mode to work, we must have SGL/DIFF=0, A2=1. A1=1. A0=0, according to what is specified in the

channel addresses table. Also, it is important to note that in order to read the data from the quadrature inputs

calculator we must read all 32 bits of data of the ADC, therefore reducing the overall sampling rate of the ADC by half.

The ADC provides us with the following information:

- Phase A and Phase B bits, dividing the period into four quadrants

- DIR bit, which indicates the direction of the rotation of the rotor

- Counter, this is a 10 bit word that, in the case of using a step down in the rotor indicates the number of times the

step down has spun. The counter increases twice per period if DIR is equal zero and decreases twice per period if

DIR equals one.

Figure 54. A to B phase

Direction of the rotor based on the DIR bit

If the rotor is rotating as the above picture, the direction bit is low.

If the rotor is rotating in the opposite direction to the above picture, the direction bit is high.

Note: This mode works only for SGL/DIFF=0, A2=1. A1=1. A0=0.

Phase A

Phase B

Cos

Sinus

Direction = 0

Direction = 1

Code 2048

Code 4095

Code 0