Sleep Mode Input (SLEEP)

The MAX9621 features an active-low SLEEP input. Pull

SLEEP

low for more than 40µs to put the device into

sleep mode for power saving. In sleep mode, the DOUT1

and DOUT2 outputs are high impedance and are pulled

high by pullup resistors. AOUT1 and AOUT2 are set to

zero-output current.

Hall Input Restart

When an input has been shut down due to a short to

ground, cycle SLEEP for 10µs to 20µs to restart the input.

If the other input is operational it is not affected. The

restart happens on the rising edge of SLEEP.

Input Current Thresholds and

Short to Ground

The input current high and low thresholds that determine

the logic level of the digital outputs are adjusted by chang-

ing the RSET value. When the RSET value changes, the

following parameters change as well: IIN_HYS, ISC, tBL,

tRAMP, tDEL, fMAX, and PR.

IIH, IIL, IIN_HYS, ISC, tRAMP, and fMAX are inversely pro-

portional to RSET and decrease as RSET increases. This

inverse relationship is linear. For example, a 10% change

in (1/RSET) results in a 10% change in current param-

eters. Conversely, time and delay parameters are linear

and directly proportional to RSET, and a 10% change in

RSET results in an 10% change in time parameters.

The difference between the maximum and minimum

threshold current limits is the min/max limit spread, which

is greater than the threshold hysteresis. The min/max

spread and the hysteresis both change by the same per-

centage as the mean of the threshold current limits. The

following equation is useful for finding the mean of the

threshold current limits given a value of RSET resistance:

(

)

0

1

II

I 0

Rm

=

+

<

×

I is the mean of the threshold current limits, R is the value

of the RSET resistance in kΩ, the constant I0 = 0.03717mA,

and the constant m = -0.001668 (1/(kΩ x mA)).

The following equation is useful for finding the value of RSET

resistance given a mean of the threshold current limits:

(

)

0

Y Y

m II 0

1

R

Y

=

+

×

<

=

Y0 = 6.2013 x 10-5 units of (1/kΩ)

To compute the typical input current thresholds from the

mean input current, it is necessary to obtain the hyster-

esis. The following equation finds the hysteresis given the

mean threshold current, I:

H = H0 + k x I (I < 0)

where H0 = -0.033463 in mA, and k = -0.08414 in mA/mA.

Input current threshold high = I - H/2, input current thresh-

old low = I + H/2.

Application Information

Use of Digital and Analog Outputs

The digital output can be used to provide the FP with an

interrupt signal that can represent a Hall sensor change

of status. DOUT1 and DOUT2 provide a time domain

output filter for robust noise immunity. See Figure 2.

The analog output can be connected to an ADC with an

appropriate load resistor, and can be used to perform

custom diagnostics.

Figure 4. Hall Input Reenergized When Open Input Is Reconnected to Hall Sensor

14V

VIN_

8V

5mA/µs

HALL INPUT RECONNECTED

TO HALL SENSOR

11.5mA

IIN_

0V

0A

TIME

TIME

VBAT - 500mV

VBAT - 25mV

MAX9621

Dual, 2-Wire Hall-Effect Sensor Interface

with Analog and Digital Outputs

www.maximintegrated.com

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