M16C30L Datasheet, PDF (131/166 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

A-D Converter
Mitsubishi microcomputers
M16C / 30L Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
A-D Converter
The A-D converter consists of one 10-bit successive approximation A-D converter circuit with a capacitive coupling
amplifier. Pins P100 to P107, P95, and P96 also function as the analog signal input pins. The direction registers of
these pins for A-D conversion must therefore be set to input. The Vref connect bit (bit 5 at address 03D716) can be
used to isolate the resistance ladder of the A-D converter from the reference voltage input pin (VREF) when the A-D
converter is not used. Doing so stops any current flowing into the resistance ladder from VREF, reducing the power
dissipation. When using the A-D converter, start A-D conversion only after setting bit 5 of 03D716 to connect VREF.
The result of A-D conversion is stored in the A-D registers of the selected pins. When set to 10-bit precision, the low
8 bits are stored in the even addresses and the high 2 bits in the odd addresses. When set to 8-bit precision, the low
8 bits are stored in the even addresses.
Table 1.17.1 shows the performance of the A-D converter. Figure 1.17.1 shows the block diagram of the
A-D converter, and Figures 1.17.2 and 1.17.3 show the A-D converter-related registers.
Table 1.17.1. Performance of A-D converter
Item
Performance
Method of A-D conversion Successive approximation (capacitive coupling amplifier)
Analog input voltage (Note 1) 0V to AVCC (VCC)
Operating clock φAD (Note 2) VCC = 3.3V fAD/divide-by-2 of fAD/divide-by-4 of fAD, fAD=f(XIN)
Resolution
8-bit or 10-bit (selectable)
Absolute precision
VCC = 3.3V • Without sample and hold function
±5LSB
• With sample and hold function (8-bit resolution)
±2LSB
• With sample and hold function (10-bit resolution)
AN0 to AN7 input : ±5LSB
ANEX0 and ANEX1 input (including mode in which external
operation amp is connected) : ±7LSB
Operating modes
One-shot mode
Analog input pins
8pins (AN0 to AN7) + 2pins (ANEX0 and ANEX1)
A-D conversion start condition • Software trigger
A-D conversion starts when the A-D conversion start flag changes to “1”
• External trigger (can be retriggered)
A-D conversion starts when the A-D conversion start flag is “1” and the
ADTRG/P97 input changes from “H” to “L”
Conversion speed per pin • Without sample and hold function
8-bit resolution: 49 φAD cycles, 10-bit resolution: 59 φAD cycles
• With sample and hold function
8-bit resolution: 28 φAD cycles, 10-bit resolution: 33 φAD cycles
Note 1: Does not depend on use of sample and hold function.
Note 2: Divide the fAD if f(XIN) exceeds 10MHZ, and make φAD frequency equal to or less than 10MHz. And
divide the fAD if VCC is less than 3.0V, and make φAD frequency equal to or lower than fAD/2.
Without sample and hold function, set the φAD frequency to 250kHZ min.
With the sample and hold function, set the φAD frequency to 1MHZ min.
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