HAL855UT-K datasheet(7/42 Pages) MICRONAS

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DATA SHEET

HAL855

Micronas

Nov. 26, 2008; DSH000149_003EN

2. Functional Description

2.1. General Function

The HAL855 is a monolithic integrated circuit which

provides an output signal proportional to the magnetic

flux through the Hall plate.

The external magnetic field component perpendicular

to the branded side of the package generates a Hall

voltage. The Hall IC is sensitive to magnetic north and

south polarity. This voltage is converted to a digital

value, processed in the Digital Signal Processing Unit

(DSP) according to the settings of the EEPROM regis-

ters, converted to the different digital output formats

(PWM and Biphase-M serial protocol) and provided by

an open-drain output transistor stage. The function

and the parameters for the DSP are explained in

Section 2.2. on page 9.

The setting of the LOCK register disables the program-

ming of the EEPROM memory for all time. This regis-

ter cannot be reset.

As long as the LOCK register is not set, the output

characteristic can be adjusted by programming the

EEPROM registers. The IC is addressed by modulat-

ing the supply voltage (see Fig. 2–1). After detecting a

command, the sensor reads or writes the memory and

answers with a digital signal on the output pin. The

output is switched off during the communication.

When no command is detected or processed and the

supply voltage is within the recommended operating

range the PWM or Biphase-M output is enabled.

It is possible to program several sensors individually if

they are in parallel to the same supply and ground line.

The selection of each sensor is done via its output pin.

Internal temperature compensation circuitry and the

choppered offset compensation enables operation

over the full temperature range with minimal changes

in accuracy and high offset stability. The circuitry also

rejects offset shifts due to mechanical stress from the

package. The non-volatile memory consists of redun-

dant EEPROM cells. In addition, the sensor IC is

equipped with devices for overvoltage and reverse-

voltage protection at all pins.

Fig. 2–1: Programming with VDD modulation

Fig. 2–2: HAL855 block diagram

HAL

855

VDD

GND

OUT

VPull-up

Temperature

Oscillator

Switched

A/D

Digital

OUT

VDD

GND

EEPROM Memory

Bandgap

Reference

Dependent

Bias

Hall Plate

Converter

Signal

Processing

Supply

Lock

Level

Control

Open-Drain Output

HAL 855

Detection

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