Sleep Mode

Sleep mode can be used in applications that do not continu-

ously require the polling of the Hall sensors. In such cases,

the µP 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 µP. 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 RSET 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

PART NO.

MANUFACTURER

WEBSITE

COMMENTS

HAL573-6

Micronas

www.micronas.com

2-wire

HAL556/560/566

Micronas

www.micronas.com

2-wire

HAL579/581/584

Micronas

www.micronas.com

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

R

VCC

IN_

X

MAX9621

MAX9621

Dual, 2-Wire Hall-Effect Sensor Interface

with Analog and Digital Outputs

www.maximintegrated.com

Maxim Integrated │ 14