AH8501 datasheet(9/19 Pages) DIODES

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AH8501

Document number: DS37512 Rev. 1 - 2

9 of 19

www.diodes.com

February 2015

AH8501

Application Note (continued)

Sensitivity and Transfer Characteristic

The device responds to the magnetic flux density perpendicular to the part marking surface. For South pole magnetic flux density increase from

0G, the output voltage will increase from VNULL and for a North magnetic pole field, the output will decrease from VNULL. The changes in the

voltage level up or down are symmetrical to VNULL and are proportional to the magnetic flux density.

The output voltage change is proportional to the magnitude and polarity of the magnetic field perpendicular to the part marking surface. This

proportionality is defined as output voltage sensitivity and is given by

SENS =

OUT B_MAX −

OUT B_MIN

MAX −

MIN

The AH8501 has a measurable magnetic field range of +/-400G and output voltage range of 0V to (255/256)VDD. Therefore sensitivity at 1.8V is

given by

SENS_1.8V =

1.8

800

= 2.25

The device has an internal ADC and DAC with a resolution of 8-bits. Therefore, the measurement resolution is 3.125G/LSB at VDD = 1.8V. In

terms of voltage, the output resolution at 1.8V is 7mV/LSB typical. The device follows the 8-bit step for transfer curve superimposed on the

VSENS above. This difference in theoretical linear value with 8-bit resolution steps produces a measurement (quantization) error at each step.

Quantization error (also measurement error) = 0.5*step = VDD/512(output voltage), OR

= Full magnetic range/512 (input magnetic field)

Transfer Curve – Output Voltage vs. Magnetic Flux Density

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.0

3.3

3.6

3.9

-500

-400

-300

-200

-100

100

200

300

400

500

Magnetic Flux Density, B (Gauss)

TA = +25 °C

3.6V

3.3V

3.0V

1.8V

1.6V

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