Section 14 A/D Converter
Rev.2.00 Jun. 28, 2007 Page 540 of 666
REJ09B0311-0200
14.7 Usage
Notes
14.7.1
Module Stop State Setting
Operation of the A/D converter can be disabled or enabled using the module stop control register.
The initial setting is for operation of the A/D converter to be halted. Register access is enabled by
clearing the module stop state. For details, see section 18, Power-Down States.
14.7.2 Permissible
Signal Source Impedance
This LSI's analog input is designed so that the conversion accuracy is guaranteed for an input
signal for which the signal source impedance is 10 k
Ω
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
Ω
, charging may be insufficient and it
may not be possible to guarantee the A/D conversion accuracy. However, if a large capacitance is
provided externally for conversion in single mode, the input load will essentially comprise only
the internal input resistance of 10 k
Ω
, 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/
µ
s or greater) (see figure 14.8). When converting a
high-speed analog signal or conversion in scan mode, a low-impedance buffer should be inserted.
Equivalent circuit of the A/D converter
This LSI
20 pF
Cin =
15 pF
10 k
Ω
Low-pass
filter
C = 0.1
µ
F
(recommended value)
Sensor output
impedance
R
≤
10 k
Ω
Sensor input
Figure 14.8 Example of Analog Input Circuit
Summary of Contents for H8SX/1650
Page 2: ...Rev 2 00 Jun 28 2007 Page ii of xxii...
Page 106: ...Section 4 Exception Handling Rev 2 00 Jun 28 2007 Page 84 of 666 REJ09B0311 0200...
Page 142: ...Section 5 Interrupt Controller Rev 2 00 Jun 28 2007 Page 120 of 666 REJ09B0311 0200...
Page 326: ...Section 8 I O Ports Rev 2 00 Jun 28 2007 Page 304 of 666 REJ09B0311 0200...
Page 470: ...Section 12 Watchdog Timer WDT Rev 2 00 Jun 28 2007 Page 448 of 666 REJ09B0311 0200...
Page 566: ...Section 14 A D Converter Rev 2 00 Jun 28 2007 Page 544 of 666 REJ09B0311 0200...
Page 574: ...Section 16 RAM Rev 2 00 Jun 28 2007 Page 552 of 666 REJ09B0311 0200...
Page 584: ...Section 17 Clock Pulse Generator Rev 2 00 Jun 28 2007 Page 562 of 666 REJ09B0311 0200...
Page 638: ...Section 19 List of Registers Rev 2 00 Jun 28 2007 Page 616 of 666 REJ09B0311 0200...
Page 668: ...Section 20 Electrical Characteristics Rev 2 00 Jun 28 2007 Page 646 of 666 REJ09B0311 0200...
Page 676: ...Appendix Rev 2 00 Jun 28 2007 Page 654 of 666 REJ09B0311 0200...
Page 688: ...Rev 2 00 Jun 28 2007 Page 666 of 666 REJ09B0311 0200...
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