Rainbow Electronics MAX9621 User Manual
Page 12
Dual, 2-Wire Hall-Effect Sensor Interface with
Analog and Digital Outputs
MAX9621
12
Sleep Mode
Sleep mode can be used in applications that do not
continuously require the polling of the Hall sensors. In
such cases, the FP can enable the MAX9621 for a short
time, check the sensor status, and then put the MAX9621
back to sleep. A blanking period follows upon exiting
sleep mode.
Remote Ground
The MAX9621 targets applications with 2-wire Hall-effect
sensors. 2-wire sensors have connections for supply and
ground. The output level is signaled by means of modula-
tion of the current drawn by the Hall sensor from its supply.
The two threshold currents for high/low are generally in the
range of 5mA to 14mA. Thus, the interfacing of a 2-wire
sensor is not simply a matter of detecting two voltage
thresholds, but requires a coarse current-sense function.
Because of the high-side current-sense structure of the
MAX9621, the device is immune to shifts between the
sensor ground, the ground of the MAX9621 and FP. This
ground-shift immunity eliminates the need for a ground-
connection wire, allowing a single-wire interface to the
Hall sensor.
Hall-Effect Sensor Selection
The MAX9621 is optimized for use with 2-wire Hall-effect
switches or with 3-wire Hall-effect switches connected
as 2-wire (Figure 5). When using a 3-wire Hall sensor the
resistor R is chosen so that the current drawn by the Hall
sensor crosses the MAX9621 current threshold when
the magnetic threshold of the Hall sensor is exceeded.
A partial list of Hall switches that can be used with the
MAX9621 is given in Table 2.
Input Current Threshold Precision
To get the best input current threshold precision, it is rec-
ommended that the R
SET
resistor be directly connected
to the BAT pin. A true Kelvin type connection is best.
Figure 5. 3-Wire Hall-Effect Switches Configured as 2-Wire
Table 2. A Partial List of Compatible Hall Switches
R
V
CC
IN_
X
MAX9621
PART NO.
MANUFACTURER
WEBSITE
COMMENTS
HAL573-6
Micronas
www.micronas.com
2-wire
HAL556/560/566
Micronas
2-wire
HAL579/581/584
Micronas
2-wire
A1140/1/2/3
Allegro
www.allegromicro.com
2-wire
A3161
Allegro
www.allegromicro.com
3-wire, optimized for 2-wire
use without added resistor
TLE4941/C
Infineon
www.infineon.com
2-wire