IC-NG Datasheet, PDF (8/21 Pages) IC-Haus GmbH – 8-BIT Sin/D CONVERTER-PROCESSOR

iC-NG
8-BIT Sin/D CONVERTER-PROCESSOR
DESCRIPTION OF FUNCTIONS
Rev D3, Page 8/21
Converter principle
iC-NG is an analog-digital tracking-type converter
(compensation process). The output value is stored in
an up/down counter. This is converted to analog volt-
age by a D/A converter and compared to the input
signal by a comparator. The comparator output con-
trols the direction input of the counter. The count direc-
tion is maintained until the output voltage of the D/A
converter, which is proportional to the output value,
corresponds to the value of the input voltage.
A × sin
SINUS / DIGITAL CONVERTER
PGA
Comparator
Resolution, Hysteresis
Binary Up/Down-Counter
Segment
MUX
A × cos
VREF
A × sin
TAN D/A
Converter
tan(phi) _tan phi _D/A
OFFS
Converter Function Adaptation
(per segment)
Fig. 4: core of the TAN D/A converter
In contrast to conventional A/D converters, the output
value in the sine/digital converter is proportional not to
the input voltage but to its phase. In the following, the
input value is referred to as “PHI“ and the output value
as “phi“.
A × SIN(n)
1. segment
e1 _PGA G × e1
GAIN = 0.5 .. 2
A × COS(n)
1
e2 45E
comparator
+
-
e2 × Ftan(n)
FA
VREF
OFFS
0E
OFFS = (-0.33 .. 0.33) × COS
The phase is available at the input in the form A x
SIN(PHI) and A x COS(PHI). From the output value,
the tangent function is formed in the feedback loop
and multiplied by COS(PHI). The result is compared to
SIN(PHI). The rule for regulation is as follows:
A(SIN(Φ)' A(COS(Φ) × TAN(φ)
Since the tangent function has pole points and cannot
be formed over a whole cycle, a cycle is divided into
eight segments. For certain segments the input signals
are reversed and the cotangent function is formed in
the feedback loop. The segment changeover function
is indicated in the following table:
Segments
Comparator Inputs
1 phi= 0°..45°
2 phi= 45°..90°
3 phi= 90°..135°
4 phi= 135°..180°
5 phi= 180°..225°
6 phi= 225°..270°
7 phi= 270°..315°
8 phi= 315°..360°
A×SIN(PHI)
A×COS(PHI)
!A×COS(PHI)
A×SIN(PHI)
!A×SIN(PHI)
!A×COS(PHI)
A×COS(PHI)
!A×SIN(PHI)
A×COS(PHI) × |TAN(phi)|
A×SIN(PHI) × |COT(phi)|
A×SIN(PHI) × |COT(phi)|
!A×COS(PHI) × |TAN(phi)|
!A×COS(PHI) × |TAN(phi)|
!A×SIN(PHI) × |COT(phi)|
!A×SIN(PHI) × |COT(phi)|
A×COS(PHI) × |TAN(phi)|
Fig. 6: segmentation
The sine/digital converter automatically runs via the
shortest route into the correct segment and thus, with
a static input signal, reaches its operating point after a
maximum of n/2 clock cycles (n corresponds to the
resolution).
A converter of the type described above will never
reach a quiescent state. With a constant input signal,
the counter would continuously increment or decre-
ment one LSB, which is prevented here by hysteresis.
A range is set up by the programmable hysteresis on
both sides of the counter value and the input signal is
checked over two clock cycles as to whether it is still
within this range. The output frequency is therefore
only half the clock frequency.
Fig. 5: converter principle