2.2. Digital Signal Processing and EEPROM
The DSP is the major part of this sensor and performs
the signal conditioning. The parameters for the DSP
are stored in the EEPROM registers. The details are
shown in
Terminology:
SENSITIVITY: name of the register or register value
Sensitivity:
name of the parameter
Group 3 contains the Micronas registers and LOCK for
the locking of all registers. The Micronas registers are
programmed and locked during production and are
read-only for the customer. These registers are used
for oscillator frequency trimming, A/D converter offset
compensation, and several other special settings.
The ADC converts positive or negative Hall voltages
(operates with magnetic north and south poles at the
branded side of the package) in a digital value. This
signal is filtered in the Digital Filter and is readable in
the ADC-READOUT register as long as the LOCK bit
is not set.
Note:
The ADC-READOUT values and the resolution
of the system depends on the filter frequency. Positive
values accord to a magnetic north pole on the branded
side of the package.
and
show typi-
cal ADC-READOUT values for the different magnetic
field ranges and filter frequencies.
– The output voltage can be calculated as:
V
OUT
∼
Sensitivity
×
B + V
OQ
The output voltage range can be clamped by setting
the registers CLAMP-LOW and CLAMP-HIGH in order
to enable failure detection (such as short-circuits to
V
DD
or GND).
The EEPROM registers consist of three groups:
Group 1 contains the registers for the adaption of the
sensor to the magnetic system:
MODE for selecting the magnetic field range and filter
frequency, TC and TCSQ for temperature characteris-
tics of the magnetic sensitivity.
Group 2 contains the registers for defining the output
characteristics: SENSITIVITY, VOQ, CLAMP-LOW,
and CLAMP-HIGH. The output characteristic of the
sensor is defined by these 4 parameters (see
and
for examples).
– The parameter V
OQ
(Output Quiescent Voltage) cor-
responds to the output voltage at B = 0 mT.
– The parameter Sensitivity is defined as:
Sensitivity =
∆V
OUT
∆B
6000
Filter = 500 Hz
1500
Filter = 2 kHz
4000
ADC-
READOUT
2000
1000
ADC-
READOUT
500
0
0
–2000
Range 150 mT
–4000
Range 90 mT
Range 75 mT
Range 30 mT
–6000
–200–150–100 –50
0
50 100 150 200 mT
B
–500
Range 150 mT
–1000
Range 90 mT
Range 75 mT
Range 30 mT
–1500
–200–150–100 –50
0
50 100 150 200 mT
B
Fig. 2–6:
Typical ADC-READOUT
versus magnetic field for filter = 500 Hz
Fig. 2–7:
Typical ADC-READOUT
versus magnetic field for filter = 2 kHz
Micronas
7
MICRONAS [ MICRONAS ]
