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HD64F3337YCP16V Datasheet, PDF (383/749 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents | |||
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Digital output
Ideal A/D
conversion
characteristic
Full-scale error
Nonlinearity
error
Actual A/D conversion
characteristic
Offset error
FS
Analog input
voltage
Figure 15.9 A/D Conversion Accuracy Definitions (2)
15.6.5 Allowable Signal-Source Impedance
The analog inputs of the H8/3337 Series and H8/3397 Series are designed to assure accurate
conversion of input signals with a signal-source impedance not exceeding 10 kâ¦. The reason for
this rating is that it enables the input capacitor in the sample-and-hold circuit in the A/D converter
to charge within the sampling time. If the sensor output impedance exceeds 10 kâ¦, charging may
be inadequate and the accuracy of A/D conversion cannot be guaranteed.
If a large external capacitor is provided, then the internal 10 k⦠input resistance becomes the only
significant load on the input. In this case the impedance of the signal source is not a problem.
A large external capacitor, however, acts as a low-pass filter. This may make it impossible to track
analog signals with a large differential coefficient (e.g. 5 mV/µs or more).
To convert high-speed analog signals, insert a low-impedance buffer.
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