IC-MR Datasheet, PDF (23/44 Pages) IC-Haus GmbH – 13-BIT S&H SIN/COS INTERPOLATOR WITH CONTROLLER INTERFACES

iC-MR 13-BIT S&H SIN/COS
preliminary
INTERPOLATOR WITH CONTROLLER INTERFACES
AMPLITUDE CONTROL
Rev A1, Page 23/44
iC-MR allows the amplitude of the output signals at
pins PSO, NSO, PCO, and NCO to be kept constant
- regardless of temperature and ageing effects - by
tracking the sensor supply. For this purpose iC-MR
has a controlled current source at pin ACO which can
power the external sensor. The driver capability of this
current source is selected by ACOR (Table 27), the
control modes by ACOT (Table 28).
ACOR
Code
00
01
10
11
Addr 0x00, bit 6:5
Function
5 mA - range
10 mA - range
25 mA - range
50 mA - range
Square control mode keeps the sum of the sine/cosine
amplitude squares at a constant value. Register ACOC
adjusts the setpoint for analog output ACO according
to Table 31.
ACOC
Code
0x00
0x01
Addr 0x00, bit 4:0
Square mode ACOT = 00
Vpp() ≈ 300 mV (60 %)
Vpp() ≈ 305 mV (61 %)
...
Vpp() ≈ 300 mV
77
77−(1.25∗Code)
0x19
...
0x1F
Vpp() ≈ 500 mV (98 %)
...
Vpp() ≈ 600 mV (120 %)
Table 27: ACO Output current range (for control oper-
ation and constant current source)
ACOT
Code
00
01
10
11
Addr 0x01, bit 0; Addr 0x00, bit 7
Function
SIN/COS square control
Sum control
Combined Sum and SIN/COS square control
Constant current source
Table 31: AC Setpoint square control
Vpp() ~~ 500 mV
Vpk() ~~ 250 mV
ϕ
As cos(ϕ)
Table 28: ACO Output control principle
LCMODE
Code
0
1
Addr 0x02, bit 3
Function
Optimized control
Standard control
Table 29: Control mode
Vt(min) Vt(max)
Figure 10: Signal monitoring with square control
(example: ACOC = 0x19; for Vt()min or
Vt()max; see Elec. Char. Nos. 809 and
810).
In sum control mode the sine and cosine DC values
(SVDC and CVDC) are added together and regulated
to the setpoint. The setpoint is configured using regis-
ter ACOD according to Table 30.
ACOD
Code
0x00
0x01
...
0x7F
Addr 0x01, bit 7:1
Sum mode ACOT = 01
VDC1 + VDC2 ≈ 166 mV
VDC1 + VDC2 ≈ 167 mV
VDC1 + VDC2
≈
166 mV
109
109−(0.6∗Code)
VDC1 + VDC2 ≈ 551 mV
As opposed to square mode, sum mode gives a higher
accuracy. However, at higher signal frequencies it can-
not compensate for a reduction in the signal amplitude
caused by the amplifier cut-off frequency of the sen-
sors. The device thus has a combined control mode
which utilizes both control modes, sum and square
(see Table 28). In this mode sum control is applied at
low frequencies, with square control coming into play
at frequencies exceeding the cut-off frequency of the
sensor’s amplifiers. So that this control mode functions
correctly, the set signal amplitude for square control
mode must be lower than that for sum control.
Table 30: DC Setpoint sum control