MA710 – 12-BIT, DIGITAL ANGLE SENSOR WITH ABZ & PWM OUTPUTS

MA710 Rev. 1.0

www.MonolithicPower.com

26

9/27/2017

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2017 MPS. All Rights Reserved.

APPENDIX A: DEFINITIONS

Effective

Resolution (3σ

noise level)

This is the smallest angle increment distinguishable from the noise. The

resolution is measured by computing three 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 state is computed. The inverse of this rate is

the minimum time between two 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.

Figure A1: Resolution, INL, Lag

INL can be obtained from the error curve

, where

is the average over 1000 sensor output and

is the mechanical

angle indicated by a high precision encoder (<0.001 deg). INL is then

computed with Equation (A1):

(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