HMC1001/1002/1021/1022

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For simpler circuits with less critical requirements for noise and accuracy, a single polarity pulse circuit may be employed

periodically (all sets or all resets). With these uni-polar pulses, several uni-polar pulses become close in performance to a

single bipolar set/reset pulse circuit.

NOISE CHARACTERISTICS

The noise density curve for a typical AMR sensor is shown in the figure below. The 1/f slope has a nominal corner

frequency near 10Hz and flattens out to a 3.8 nV/sqrtHz slope. This is approximately equivalent to the Johnson noise (or

white noise) for an 850 ohm resistor, the typical bridge resistance. To relate the noise density voltage to the magnetic

fields, use the following expressions:

For Vbridge = 5V and Sensitivity = 3.2mV/V/gauss, the bridge output (Voutput) is 16mV/gauss

The noise density at 1Hz is about 30nV/sqrtHz or 1.8 micro-gauss/sqrtHz

1/f noise (0.1 to 10Hz) = 30 * sqrt[(ln10/0.1)] nV = 64nV (rms) = 4 micro-gauss (rms) = 27 micro-gauss (pk-pk)

White noise (BW = 1kHz) = 3.8 * sqrt[BW] nV = 120nV (rms) = 50 micro-gauss (pk-pk)