DATA SHEET
HAL855
2. Functional Description
2.1. General Function
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.
The HAL855 is a monolithic integrated circuit which
provides an output signal proportional to the magnetic
flux through the Hall plate.
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.
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.
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.
HAL
855
The setting of the LOCK register disables the program-
ming of the EEPROM memory for all time. This regis-
ter cannot be reset.
VPull-up
8
7
6
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.
0
5
V
OUT
DD
GND
Fig. 2–1: Programming with VDD modulation
V
DD
Temperature
Dependent
Bias
Bandgap
Reference
Oscillator
Digital
Signal
Processing
OUT
HAL855
Open-Drain Output
Switched
Hall Plate
A/D
Converter
Supply
Level
Detection
Lock
Control
EEPROM Memory
GND
Fig. 2–2: HAL855 block diagram
Micronas
Nov. 26, 2008; DSH000149_003EN
7
MICRONAS [ MICRONAS ]
