Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
8
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Quiescent Current Duty Cycle Output Programming
Resolution The programming resolution for any device is half
of its programming step size. Therefore, the typical programming
resolution will be:
Err
PGD(Q)
(typ)
=
0.5 × Step
D(Q)
(typ)
.
(2)
Quiescent Duty Cycle Output Drift through Tempera-
ture Range Due to internal component tolerances and thermal
considerations, the Quiescent Duty Cycle Temperature Coef-
ficient, D
TC(Q)
, may drift from its nominal value over the operat-
ing ambient temperature, T
A
. For purposes of specification, the
Quiescent Duty Cycle Output Drift Through Temperature Range,
D
(Q)
(% D), is defined as:
D
(Q)(TA)
– D
(Q)(25°C)
∆D
(Q)
=
,
(3)
where D
(Q)(TA)
is the quiescent duty cycle measured at T
A
and
D
(Q)(25°C)
is the quiescent duty cycle measured at 25°C.
Sensitivity The presence of a south polarity magnetic field,
perpendicular to the branded surface of the package face,
increases the current duty cycle from its quiescent value toward
the maximum duty cycle limit. The amount of the current duty
cycle increase is proportional to the magnitude of the magnetic
field applied. Conversely, the application of a north polarity
field decreases the current duty cycle from its quiescent value.
This proportionality is specified as the magnetic Sensitiv-
ity, Sens ((% D)/G), of the device, and it is defined for bipolar
devices as:
D
(BPOS)
– D
(BNEG)
BPOS – BNEG
Sens
=
,
(4)
and for unipolar devices as:
D
(BPOS)
– D
(Q)
BPOS
Sens
=
,
(5)
where BPOS and BNEG are two magnetic fields with opposite
polarities.
Guaranteed Sensitivity Range The magnetic Sensitivity can
be programmed from its initial value, Sens
init
, to a value within
the Guaranteed Sensitivity Range limits: Sens
Range
(min) and
Sens
Range
(max).
Average Sensitivity Step Size Refer to the Average Qui-
escent Current Duty Cycle Step Size section for a conceptual
explanation.
Sensitivity Programming Resolution Refer to the Quies-
cent Current Duty Cycle Programming Resolution section for a
conceptual explanation.
Carrier Frequency Target The PWM
OUT
signal Carrier
Frequency Programming Range, f
PWM
, can be programmed to its
typical value of 1 kHz.
Average Carrier Frequency Step Size Refer to the Average
Quiescent Current Duty Cycle Step Size section for a conceptual
explanation.
Carrier Frequency Programming Resolution Refer to the
Quiescent Durrent Duty Cycle Programming Resolution section
for a conceptual explanation.
Sensitivity Temperature Coefficient Device sensitiv-
ity changes as temperature changes, with respect to its pro-
grammed Sensitivity Temperature Coefficient, Sens
TC
. Sens
TC
is programmed at 150°C, and calculated relative to the nominal
sensitivity programming temperature of 25°C. Sens
TC
(%/°C) is
defined as:
Sens
T2
– Sens
T1
Sens
T1
T2–T1
1
Sens
TC
=
×
100%
,
(6)
where T1 is the nominal Sens programming temperature of 25°C,
and T2 is the programming temperature of 150°C. The expected
value of Sens through the full ambient temperature range,
Sens
EXPECTED(TA)
, is defined as:
Sens
T1
× [100% +Sens
TC
(T
A
–T1)]
Sens
EXPECTED(TA)
=
.
100 %
(7)
Sens
EXPECTED (TA)
should be calculated using the actual measured
values of Sens
T1
and Sens
TC
rather than programming target
values.
Sensitivity Drift Through Temperature Range Second
order Sensitivity Temperature Coefficient effects cause the mag-
netic Sensitivity, Sens, to drift from its expected value through
the operating ambient temperature range, T
A
. For purposes of
specification, the Sensitivity Drift Through Temperature Range,
Sens
TC
, is defined as:
Sens
TA
– Sens
EXPECTED(TA)
Sens
EXPECTED(TA)
∆Sens
TC
=
×
100%
.
(8)
Sensitivity Drift Due to Package Hysteresis Package
stress and relaxation can cause the device Sensitivity at T
A
=
25°C to change during and after temperature cycling.
