Uf251_01d_oi_e.doc / Aug-16
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With the standard resolution mode there is an auxiliary output frequency divider available
(programmable by register “Output Divider”).
By well-aimed selection of the settings of “High Frequency” and “Output Divider” it is possible
to optimize the overall accuracy and the dead band around zero. For instance, to improve
accuracy, we can decrease “High Frequency” and “Output Divider” but concurrently this entails
an enlargement of the dead band. For better understanding of this coherence the following
example shows two possibilities of settings:
Example: You like to get an output frequency of 0 Hz with 5 V input voltage and 20 kHz output
frequency with 9 V input voltage.
Option (a):
Low Voltage
:
5.000
High Voltage
:
9.000
Low Frequency
:
0
High Frequency
:
20.000
High Resolution
:
0 (standard resolution)
Output Divider
:
1 (no division)
This setting results in an accuracy of [20 kHz : 67kHz x 0.1%], therefore approx. 0.03%. But our
lowest possible frequency is 62.5 Hz. This means we will need to accept a dead band window
around zero which is
10V x
= 0.031V
62,5 Hz
20.000 Hz
The unit will generate zero output frequency in a range of 5 Volts +/- 31 mV
Option (b):
Low Voltage
:
5.000
High Voltage
:
9.000
Low Frequency
:
0
High Frequency
:
60.000 ( = 3 x 20.000 )
High Resolution
:
0 (standard resolution)
Output Divider
:
3 (60 kHz : 3 = 20 kHz as required)
This setting results in an overall accuracy of 0.1%. However the lowest possible frequency is
now 1/3 of 62.5 Hz, this means 20.8 Hz. Therefore, our dead band around zero will only be
10V x
= 0.010V
20,8 Hz
20.000 Hz
We will have zero output frequency in a range of 5 V ±10 mV.
