MA302 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & UVW OUTPUTS

MA302 Rev. 1.1

www.MonolithicPower.com

28

2/7/2020

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APPENDIX A: DEFINITIONS

Effective

Resolution (3σ

noise level)

The smallest angle increment distinguishable from the noise. The

resolution is measured by computing 3 times

σ (the standard deviation

in degrees) taken over 1,000 data points at a constant position. The

resolution in bits is obtained with log2(360/6σ).

Refresh Rate

Rate at which new data points are stored in the output buffer.

ABZ Update Rate

Rate at which a new ABZ sate is computed. The inverse of this rate is

the minimum time between 2 ABZ edges.

Latency

The time elapsed between the instant when the data is ready to be read

and the instant at which the shaft passes that position. The lag in

degrees is

, where

������ is the angular velocity in deg/s.

Power-Up Time

Time until the sensor delivers valid data starting at power-up.

Integral Non-Linearity

(INL)

Maximum deviation between the average sensor output (at a fixed

position) and the true mechanical angle.

It can be obtained from the error curve

, where

is the average over 1,000 sensor outputs, and

is the

mechanical angle indicated by a high precision encoder (<0.001 deg).

The INL is then computed with:

2

))

(

min(

))

(

max(

a

err

a

err

INL





(A1)

Drift

Angle variation rate when one parameter is changed (e.g.: temperature,

VDD) and all the others, including the shaft angle, are maintained

constant.

0

50

100

150

200

250

300

350

400

0

100

200

300

400

500

600

700

rotor position (deg)

resolution

( ± 3

)

ideal

sensor output

INL

lag

sensor out

best straight fit