KMT36H 360° Angular Sensor
•
•
•
•
AMR Sensor with 360° capability
3
TDFN outline 2.5x2.5x0.75 mm
Three 120° phase-shifted signals
Moderate field strength requirements
DESCRIPTION
The
KMT36H
is a magnetic field sensor utilizing the anisotropic magneto resistance effect. Therefore
the sensor is sensing the
magnetic field direction
rather than the magnetic field strength. The sensor
contains three Wheatstone bridges rotated by 120°. A rotating magnetic field (typical strength 25 kA/m
in the sensor plane) will result in three sinusoidal output signals with a period of 180°, phase shifted by
60° field angle. By use of a modified
atan
algorithm the field angle can be calculated with high
accuracy.
As an unique feature, the KMT36H is able to measure full 360° by utilizing an additional magnetic field
which is generated by a planar coil that is integrated on the chip. The 180°/360° determination is done
by a simple sign distinction and may be computed periodically or only once at power up.
FEATURES
•
•
•
•
•
Ideal for harsh environments due to
magnetic sensing principle
Contactless absolute angular measurement
over 360°
Accuracy better than +/- 0.5°
Three bridge signals with 120° phase
difference
3
Tiny TDFN-housing 2.5 x 2.5 x 0.8 mm
APPLICATIONS
•
•
•
•
•
Absolute angle measurement
Potentiometer replacement
Motor motion control
Camera positioning
Robotics
KMT36H Rev 5
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2013-April
KMT36H 360° Angular Sensor
CHARACTERISTIC VALUES
Parameter
Condition
Symbol
Min
Typ
Max
Unit
Mechanical dimensions - TDFN
Length
Width
Height
Mechanical dimensions - SO8
Length
Width
Height
Operating limits
Supply voltage
Coil current
Operating temperature
Storage temperature
Parameter
Sensor specification
Applied magnetic field
Bridge resistance
max. signal range
Offset voltage 4)
Hysteresis 1)
(Repeatability)
Accuracy 1)
TC of amplitude
TC of bridge resistance
Coil resistance
Thermal resistance
(junction-ambient)
2), 3)
T = 25 °C
T = 25 °C, H = 25 kA/m
T = 25 °C
H = 25 kA/m
H = 25 kA/m
H = 25 kA/m, 5)
5)
T = 25 °C
T
amb
= 25°C, 6)
H
R
B
∆V/V
CC
V
OFF
/V
CC
Hyst
∆α
TC
AMP
TC
R
R
COIL
R
thJ/A
75
15
2.4
18
-3
0.15
0.15
-0.32
+0.32
100
280
150
25
3.0
22
60
3.6
26
+3
0.30
0.30
kA/m
kΩ
mV/V
mV/V
deg
deg
%/K
%/K
Ω
K/W
Condition
Symbol
T = 25 °C, H = 25 kA/m
V
CC
I
COIL
-40
-40
Min
Typ
5
20
12
50
+125
+125
Max
V
mA
°C
°C
Unit
X
Y
Z
4.9
6.0
1.75
mm
mm
mm
X
Y
Z
2.5
2.5
0.75
mm
mm
mm
1) Hysteresis and accuracy are depending nearly inversely proportional on the magnetic field strength. The accuracy is defined
as the max. angular difference between actual field angle and measured angle calculated from the third and fifth harmonics
of the Fourier spectrum. The hysteresis is defined as angular difference between left and right turn.
2) Generated with reference magnet 67.044 Magnetfabrik Bonn (25 kA/m @ 5.2 mm distance).
3) Minimum value depends on decreasing accuracy, upper limit on decreasing coil influence. Both are no absolute limits, but
depend on the given application requirements.
4) Offset voltages measured as difference voltages V
O1
-V
O2
, V
O2
-V
O3
and V
O3
-V
O1
in relation to V
CC
.
5) Reference temperature Tref = -25 °C, calculated from values at -25°C and +125 °C
6) TDFN soldered on standard test PCB, heat sink without solder connection
KMT36H Rev 5
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2013-April
KMT36H 360° Angular Sensor
BLOCK DIAGRAM
V
COIL
+ 5
n. c.
V
COIL
-
V
O3
8
4 V
O1
V
CC
GND
1 V
O2
Figure 1:
internal and external connections (TDFN and SO8, Chip)
SENSOR OUTLINE
The sensitive area is
positioned in the center of
the housing.
Figure 2:
SO8 outline
KMT36H Rev 5
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2013-April
KMT36H 360° Angular Sensor
The sensitive area is
positioned in the
center of the housing.
The bottom plate is
designated to be a
heat sink. It has no
electrical connection
to any pin.
Figure 3:
TDFN outline
Pin Assignment for TDFN and SO8:
Pin
1
2
3
4
5
6
7
8
Symbol
V
O2
GND
V
CC
V
O1
V
COIL
+
n. c.
V
COIL
-
V
O3
Function
signal output 2
negative supply voltage
positive supply voltage
signal output 1
positive coil input
not connected
negative coil input
signal output 3
Recommended Solder Layout for TDFN:
Recommended solder reflow process according to IPC/JEDEC J-STD-020D (Pb-Free Process)
TAPE AND REEL PACKAGING INFORMATION
DESCRIPTION
KMT36H
REEL SIZE
7”
UNITS/REEL
3,000
PIN 1 ORIENTATION
Top-right of sprocket hole
side
Top-left of sprocket hole
side
NOTE
KMT36H/SO
13”
2,500
KMT36H Rev 5
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2013-April
KMT36H 360° Angular Sensor
TYPICAL PERFORMANCE CURVES
0
90
180
270
360
0
90
180
270
360
field angle in deg
field angle in deg
V1 = Vo2-Vo1
V2 = Vo3-Vo2
V3 = Vo1-Vo3
V1(+Icoil) - V1(-Icoil)
V3(+Icoil) - V3(-Icoil)
V2(+Icoil) - V2(-Icoil)
Figure 3:
output voltages
Figure 4:
output voltage change due to coil influence
SIGNAL EVALUATION
180° EVALUATION
As output voltages (V
1
, V
2
, V
3
) we use the three possible differences between the three signal outputs
(see fig. 3). At first the true offsets must be subtracted from the raw signals. The field angle
α
in a
180°-range then can be calculated in the following manner:
Vn
+
1
2
⋅
1
α
= ⋅
arctan
Vm
2
3
Using the three possible combinations of output signals (m,n = 1,2 ; 2,3 ; 3,1) three results are
obtained, which can be averaged to increase accuracy. Comparing the three results gives additional
information about their reliability.
360° EVALUATION
In order to distinguish between
α
and
α+180°
two additional measurements are needed: one with
positive, the other with negative coil current. In the next step the change in the signals due to the
influence of the coil current must be calculated. The sign of these coil-induced output voltage changes
gives the 360°-information by case differentiation (see
figure 4).
In principle, this 360° discrimination
needs to be computed only once at start up. Nevertheless, it is recommended to check the
measurement periodically.
KMT36H Rev 5
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2013-April
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