MLX90215_12 Datasheet, PDF (12/14 Pages) Melexis Microelectronic Systems – Position Programmable Linear Hall Effect Sensor

MLX90215
Position Programmable
Linear Hall Effect Sensor
12 Application Notes
Linear Precision Current Sensor
The Programmable gain, offset, and temperature
compensation of MLX90215 allows great flexiblity in
the design of a current sensor.
Current flowing through a conductor can produce a
proportional magnet field. The MLX90215 can then
produce an output voltage proportional to the current.
Using the programmable gain and offset function the
output of the MLX90215 can be adjusted to sense a
wide range of current allowing for a flexible design.
Slotted Torroid Example Assuming infinite
permeabilty of the core, the magnetic field through the
air gap produced by a single wire turn is given by
equation 2
Equation 2
Where: I = current in Amperes
B = magnetic field in Tesla
lg = length of air gap in Meters
uo = Permeability of free space (4π10-7H/m)
This equation is a close estimate for the field in the air
gap, but does not take into account magnetic losses in
the core, fringing effects, and mechanical tolerances of
the air gap. The programmable MLX90215 can be
adjusted to compensate for these errors simplifying the
design. The temperature compensation of MLX90215
can also be adjusted to counteract temperature losses of
core.
For sensing a current ±100A, with an air gap of 2mm
equation 2 yields a magnetic field range of ±63mT. The
output range of the MLX90215 is 0.5V to 4.5V (4V full
scale). Equations 3a and 3b yield a sensitivity of 32mV/
mT and a Voq of 2.5V.
Magnetic Suppliers:
Elna Ferrites Technologies Inc
Eastern Components
Fair Rite Products Corp
Equation 3
a) S = 4000mV/ 126mT
b) Voq = 4V/2 + 0.5V
The resulting gain of the current sensor is 20mV/A with
an offset of 2.5V. For best results it is recommend that
MLX90215 be programmed with a Voq of 50% Vdd 1/2
Vdd bit set.
3901090215
Rev 008
Page 12 of 14
Nov/12