FM3 MB9B500 Series - Microcontrollers - Fujitsu
FM3 MB9B500 Series - Microcontrollers - Fujitsu
FM3 MB9B500 Series - Microcontrollers - Fujitsu
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(Continued)<br />
<strong>MB9B500</strong> <strong>Series</strong><br />
The output impedance of the external circuit connected to the analog input affects the sampling time of the<br />
A/D converter. Design the output impedance of the output circuit such that the required sampling time is<br />
less than the value of Ts calculated from the following equation.<br />
(Equation 1)<br />
Ts = (Rin + Rext) × Cin × 7<br />
Ts : Sampling time<br />
Rin : input resistance of A/D = 2.6kΩ 4.5 AVCC 5.5<br />
input resistance of A/D = 12.1kΩ 2.7 AVCC 4.5<br />
Cin : input capacity of A/D = 8.5pF<br />
Rext : Output impedance of external circuit<br />
If the sampling time is set as 400ns (when 4.5 AVCC 5.5),<br />
400ns (2.6kΩ + Rext) × 8.5pF × 7<br />
Rext 4.1kΩ<br />
And the impedance of the external circuit therefore needs to be 4.1kΩor less.<br />
DS706-00010-1v0-E<br />
93
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