HAL880
2.2. Digital Signal Processing and EEPROM
The DSP is the main 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 Fig. 2–3 on page 7.
DATA SHEET
A/D converter offset compensation, and several other
special settings.
An external magnetic field generates a Hall voltage
on the Hall plate. The ADC converts the amplified
positive or negative Hall voltage (operates with mag-
netic north and south poles at the branded side of the
package) to a digital value. The digital signal is
filtered in the internal low-pass filter and manipulated
according to the settings stored in the EEPROM. The
digital value after signal processing is readable in the
D/A-READOUT register. Depending on the program-
mable magnetic range of the Hall IC, the operating
range of the A/D converter is from
−30
mT … +30 mT
up to
−100
mT … +100 mT.
During further processing, the digital signal is multi-
plied with the sensitivity factor, added to the quiescent
output voltage and limited according to the clamping
voltage. The result is converted to an analog signal
and stabilized by a push-pull output transistor stage.
The D/A-READOUT at any given magnetic field
depends on the programmed magnetic field range, the
low-pass filter, TC values, CLAMP-LOW and
CLAMP-HIGH. The D/A-READOUT range is min. 0
and max. 16383.
Terminology:
SENSITIVITY: name of the register or register value
Sensitivity:
name of the parameter
The EEPROM registers consist of four 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,
TCSQ and TC-range for the 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.
– The parameter V
OQ
(Output Quiescent Voltage) cor-
responds to the output voltage at B = 0 mT.
– The parameter Sensitivity defines the magnetic sen-
sitivity:
Δ
V
OUT
-
Sensitivity
= ----------------
Δ
B
Note:
During application design, it should be taken
into consideration that the maximum and mini-
mum D/A-READOUT should not saturate in the
operational range of the specific application.
– The output voltage can be calculated as:
V
OUT
∼
Sensitivity
×
B
+
V
OQ
Range
The RANGE bits are bit 2 and 3 of the MODE register;
they define the magnetic field range of the A/D
converter.
Magnetic Field Range
−30mT...30
mT
−60
mT...60 mT
−80
mT...80 mT
−100
mT...100 mT
RANGE
0
1
2
3
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 and open connections).
Group 3
contains the general purpose register GP.
The GP register can be used to store customer infor-
mation, like a serial number after manufacturing.
Micronas will use this GP REGISTER to store informa-
tion such as lot number, wafer number, x and y posi-
tion of the die on the wafer, etc. This information can
be readout by the customer and stored in its own data
base or it can stay in the sensor as it is.
Group 4
contains the Micronas registers and LOCK
for the locking of all registers. The Micronas registers
are programmed and locked during production. These
registers are used for oscillator frequency trimming,
8
Feb. 23, 2009; DSH000152_001EN
Micronas
MICRONAS [ MICRONAS ]
