h8s-2635 Renesas Electronics Corporation., h8s-2635 Datasheet - Page 753

• Manufacturer Part Number: h8s-2635
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

Section 17 A/D Converter
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 k 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
k , 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 k , 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.
Rev. 6.00 Feb 22, 2005 page 693 of 1484
REJ09B0103-0600