3054 Datasheet, PDF (4/12 Pages) Allegro MicroSystems – MULTIPLEXED TWO-WIRE HALL-EFFECT SENSOR ICs

3054
MULTIPLEXED
TWO-WIRE
HALL-EFFECT SENSOR ICs
ADDRESSING PROTOCOL
Magnetic Operate Point (B_OP)
Minimum magnetic field required to switch ON the
Hall amplifier and switching circuitry of the addressed
sensor. This circuitry is only active when the sensor is
addressed.
Magnetic Release Point (B_RP)
Magnetic field required to switch OFF the Hall
amplifier and switching circuitry after the output has been
switched ON. When a device is deactivated by changing
the bus address, all magnetic memory is lost.
A device may be addressed by changing the supply
voltage as shown in Figure 1. A preferred addressing
protocol is as follows: the bus supply voltage is brought
low (<2.5 V) so that all devices on the bus are reset. The
voltage is then raised to the address LOW voltage (V_L) and
the bus quiescent current is measured. The bus is then
toggled between V_L and V_H (address HIGH voltage), with
each positive transition representing an increment in the
bus address. After each voltage transition, the bus current
may be monitored to check for diagnostic and signal
responses from sensor ICs.
Magnetic Hysteresis (B_HYS)
Difference between the B_OP and B_RP magnetic field
thresholds.
Sensor Addressing
When a sensor detects a bus address equal to its
factory-programmed address, it responds with an increase
in its supply current drain ( I_S) during the next HIGH portion
BUS
VOLTAGE
V
H
VCLH
V
CHL
VL
V _RST
0
IS
SENSOR 02
CURRENT
WITH NO
MAGNETIC
FIELD
I _QL
I _QH
0
IS
SENSOR 03
CURRENT
WITH
MAGNETIC
FIELD
I _QL
I _QH
0
IS
TOTAL
BUS CURRENT
WITH
MAGNETIC
FIELD AT
SENSOR 03
n • I _QL
n • IQH
0
RESET
DIAGNOSTIC
ADDRESS 01
FIGURE 1
BUS TIMING
DIAGNOSTIC
ADDRESS 02
DIAGNOSTIC
ADDRESS 03
DIAGNOSTIC
ADDRESS 04
DIAGNOSTIC
ADDRESS n
t _plh
t _phl
SENSOR 02 —
DIAGNOSTIC CURRENT
SENSOR 03 — DIAGNOSTIC
AND SIGNAL CURRENTS
SENSOR 01
NOT PRESENT
RESET
DIAGNOSTIC
ADDRESS 01
SENSOR 01
NOT PRESENT
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