HAL815 datasheet(7/24 Pages) MICRONAS

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ADVANCE INFORMATION

HAL 815

Micronas

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.

Terminology:

SENSITIVITY: name of the register or register value

Sensitivity:

name of the parameter

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 the temperature characteristics of the mag-

netic 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 Fig. 2–4

and Fig. 2–5 for examples).

– The parameter VOQ (Output Quiescent Voltage) cor-

responds to the output voltage at B = 0 mT.

– The parameter Sensitivity defines the magnetic sen-

sitivity:

– The output voltage can be calculated as:

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

VDD or GND and open connections).

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.

An external magnetic field generates a Hall voltage on

the Hall plate. The ADC converts the amplified positive

or negative Hall voltage (operates with magnetic north

and south poles at the branded side of the package) to

a digital value. Positive values correspond to a mag-

netic north pole on the branded side of the package.

The digital signal is filtered in the internal low-pass fil-

ter and is readable in the ADC-READOUT register.

Depending on the programmable magnetic range of

the Hall IC, the operating range of the A/D converter is

from

−30 mT...+30 mT up to −150 mT...+150 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 ADC-READOUT at any given magnetic field

depends on the programmed magnetic field range but

also on the filter frequency. Fig. 2–6 shows the typical

ADC-READOUT values for the different magnetic field

ranges with the filter frequency set to 2 kHz. The rela-

tionship between the minimum and maximum ADC-

READOUT values and the filter frequency setting is

listed in the following table.

∆V

OUT

∆B

Sensitivity =

VOUT ∼ Sensitivity × B + VOQ

Filter Frequency

ADC-READOUT RANGE

80 Hz

−3968...3967

160 Hz

−1985...1985

500 Hz

−5292...5290

1 kHz

−2646...2645

2 kHz

−1512...1511

–2000

–1500

–1000

–500

500

1000

1500

2000

–200–150–100 –50

50 100 150 200 mT

ADC-

READOUT

Range 150 mT

Filter = 2 kHz

Range 90 mT

Range 60 mT

Range 30 mT

Fig. 2–6: Typical ADC-READOUT

versus magnetic field for filter = 2 kHz

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