HD64F2638F20J Datasheet, PDF (753/1512 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

H8S/2639, H8S/2638, H8S/2636,
H8S/2630, H8S/2635 Group
Digital output
Full-scale error
Section 17 A/D Converter
Ideal A/D conversion
characteristic
Nonlinearity
error
Actual A/D conversion
characteristic
Offset error
FS
Analog
input voltage
Figure 17-10 A/D Conversion Precision Definitions (2)
Permissible Signal Source Impedance: The chip's analog input is designed so that conversion
precision is guaranteed for an input signal for which the signal source impedance is 10 kΩ or less.
This specification is provided to enable the A/D converter’s sample-and-hold circuit input
capacitance to be charged within the sampling time; if the sensor output impedance exceeds 10
kΩ, charging may be insufficient and it may not be possible to guarantee the A/D conversion
precision.
However, if a large capacitance is provided externally, the input load will essentially comprise
only the internal input resistance of 10 kΩ, and the signal source impedance is ignored.
However, since a low-pass filter effect is obtained in this case, it may not be possible to follow an
analog signal with a large differential coefficient (e.g., 5 mV/µs or greater).
When converting a high-speed analog signal, a low-impedance buffer should be inserted.
REJ09B0103-0800 Rev. 8.00
May 28, 2010
Page 703 of 1458