IC-PMX Datasheet, PDF (18/27 Pages) IC-Haus GmbH – ENERGY HARVESTING MULTITURN COUNTER/ENCODER

iC-PMX
ENERGY HARVESTING MULTITURN COUNTER/ENCODER
V(HOP)-V(HON)
0 mV
Rev A3, Page 18/27
hall sensor
H0
H1
H2
H3
measurement phase ⁰
1
2
3
0
1
2
3
0
1
2
3
0
1
2
3
Figure 10: Hall Amplifier Output Voltages
Singleturn Sensors
The singleturn Hall sensors (H0, H1, H2, H3) are ar-
ranged in a circle with a diameter of 3.25 mm, which is
placed in the center of the package as shown on page 5
and on page 6. Fig. 6 shows the position of the Hall
sensors with respect to the Pin 1 mark.
The singleturn sensors are temporarily disabled while
VDD or VCC are below VDDOK (brownout protection).
If a magnetic south pole comes close to the surface of
the package, the resulting magnetic field has a positive
component in the +z direction (i.e. from the top of the
package). This results in an increase of the voltage
difference between HOP and HON during the measure-
ment phases 0 and 2. In the measurement phases 1
and 3 it results in a decrease of the voltage difference
(see fig. 10). The common mode voltage of HOP and
HON is V(VUP)/2.
Four measurements with constant amplifier gain should
be done for each Hall sensor to remove first and second
order offset errors. This results in 16 A/D values which
can be reduced to two linearly independent quantities:
Q₀ =(H0, 0 − H0, 1) + (H0, 2 − H0, 3)
− ((H2, 0 − H2, 1) + (H2, 2 − H2, 3))
Q₁ =(H3, 0 − H3, 1) + (H3, 2 − H3, 3)
− ((H1, 0 − H1, 1) + (H1, 2 − H1, 3))
Q₀ is proportional to sin(α) and Q₁ is proportional to
cos(α) if the magnetic field is generated by a diamet-
rically magnetized, cylindrical permanent magnet as
shown in fig. 7.
Singleturn Hall Output Selection
The opcodes 0x10 to 0x1f can be used to choose the
singleturn Hall sensor voltage which can be measured
between the pins HOP and HON.
These commands are executed when the rising edge
of NCS is received. This is visualized in fig. 3 by the
signal change on HOP/HON. The value of OP1 and
OP0 selects the measurement phase, the value of OP3
and OP2 selects the Hall sensor (see table 12).
OPCODE
0x10...0x1f
OP3...OP2 Select Hall sensor (0...3)
OP1...OP0 Select measurement phase (0...3)
Table 12: Fast Hall Sensor Selection
Combined Singleturn Gain and Output S selection
Opcode 0x20 must be used if the Hall amplifier should
be disabled or its gain has to be changed. Table 13
shows the coding of the singleturn parameters within
the data byte. The gain is changed straightaway with
the 16th rising edge of SCK, the output selection is
changed when the rising edge of NCS is received.
Singleturn
Parameters
DB7...DB5 GAIN(2:0); gain of the singleturn Hall amplifier (0...7)
DB4
DIS7; disable singleturn sensors, default value: 0
DB3...DB2 SENSOR(1:0); select Hall sensor (0...3)
DB1...DB0 PHASE(1:0); select measurement phase (0...3)
Table 13: Singleturn Parameters
Switching the Singleturn Output Selection with Pin
SH
Pin SH can be used to change the singleturn output
selection if pin NCS is high.
An internal state machine switches to the next output
selection whenever the voltage on pin SH changes.
The sequence of output selections is fixed and docu-
mented in fig. 10. The minimum delay between switch-
ing commands is 100 ns, as documented in the Elec-
trical Characteristics, section Timing Parameter SPI
Slave Interface. The active output selection can be
read with opcode 0x28, and it is possible to set an
arbitrary start value with the SPI commands.