DATA SHEET
HAL855
4. Application Notes
4.1. Use of Two HAL855 in Parallel Operation
Micronas recommends the following application cir-
cuits for HAL855. The first is recommended for appli-
cations with connection to a regualted 5 V supply; the
second schould be used for applications connected
dicrectly to the car battery and a pull-up to a 5 V line.
Two different HAL855 sensors which are operated in
parallel to the same supply and ground line can be
programmed individually. In order to select the IC
which should be programmed, both Hall ICs are deac-
tivated by the “Deactivate” command on the common
supply line. Then, the appropriate IC is activated by an
“Activate” pulse on its output. Only the activated sen-
sor will react to all following read, write, and program
commands. If the second IC has to be programmed,
the “Deactivate” command is sent again, and the sec-
ond IC can be selected.
For both circuits, it is recommended to connect a
ceramic 4.7 nF capacitor between ground and the sup-
ply voltage, respectively, the output pin.
System side
Sensor side
Detailed information can be found in the application
note for the programmer board.
V
= 5 V ±0.5 V
supply
1
2
3
V
C
= 4.7 nF
DD
P
GND
OUT
C = 4.7 nF
L
V
DD
R
pull-up
OUT A & Select A
OUT B & Select B
Fig. 4–1: Application circuit HAL855
HAL855
HAL855
Sensor A
Sensor B
10 nF
V
= 5 V ±0.5 V
pull-up
4.7 nF
4.7 nF
System side
Sensor side
= 120 Ω
GND
V
= 8 V...18 V
supply
R
C
P
P
1
V
= 4.7 nF
DD
Fig. 4–3: Parallel operation of two HAL855
2
3
GND
OUT
C = 4.7 nF
L
R
pull-up
4.2. Measurement of a PWM Output Signal
Fig. 4–2: Application circuit HAL855 for connection
with car battery
In case that the PWM output mode is activated, the
magnetic field information is coded in the duty cycle of
the PWM signal. The duty cycle is defined as the ratio
between the high time “s” and the period “d” of the
PWM signal (see Fig. 4–4).
Note: The PWM signal is updated with the falling
edge. Hence, for signal evaluation, the trigger-
level must be the falling edge of the PWM sig-
nal.
Out
d
s
Vhigh
Vlow
time
Update
Fig. 4–4: Definition of PWM signal
Micronas
Nov. 26, 2008; DSH000149_003EN
27
MICRONAS [ MICRONAS ]
