M32CSLASH8B datasheet(285/406 Pages) RENESAS

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M32C/8B Group

18. A/D Converter

Preliminary specification

Specifications in this manual are tentative and subject to change.

REJ09B0450-0050 Rev.0.50 Oct 31, 2008

Page 268 of 385

18.2.6

External Operating Amplifier (Op-Amp) Connection Mode

In external op-amp connection mode, multiple analog voltage can be amplified by one external op-amp using

extended analog input pins, ANEX0 and ANEX1.

When bits OPA1 and OPA0 are set to 11b (external op-amp connection), voltage applied to pins AN_0 to AN_7

are output from the ANEX0. Amplify this output signal by external op-amp and apply it to the ANEX1.

Analog voltage applied to ANEX1 is converted to a digital code and the A/D conversion result is stored into the

corresponding AD0i register (i = 0 to 7). The A/D conversion rate varies depending on the response

characteristics of the external op-amp. The ANEX0 pin cannot be connected to the ANEX1 pin directly.

Set bits APS1 and APS0 in the AD0CON2 register to 00b (AN_0 to AN_7, ANEX0, ANEX1).

Figure 18.8 shows a connection example of external op-amp connection mode.

Table 18.12

Extended Analog Input Pin Settings

Figure 18.8

Connection Example in External Op-Amp Connection Mode

18.2.7

Power Consumption Reduce Function

When not using the A/D converter, the VCUT bit in the AD0CON1 register can disconnect the resistor ladder

of the A/D converter from the reference voltage input pin (VREF). As a result, power consumption can be

reduced by shutting off any current flow into the resistor ladder from the VREF pin.

When using the A/D converter, set the VCUT bit to 1 (VREF connected) prior to setting the ADST bit in the

AD0CON0 register to 1 (A/D conversion starts).

Do not set the VCUT bit to 0 (VREF not connected) during A/D conversion.

Even if the VCUT bit is set to 0, VREF remains connected to the D/A converter.

AD0CON1 Register

ANEX0 Function

ANEX1 Function

OPA1 Bit

OPA0 Bit

Not used

P9_5 as an analog input

Not used

P9_6 as an analog input

Output to external op-amp

Input from external op-amp

Successive conversion register

AN_0

AN_2

AN_1

AN_3

AN_4

AN_5

AN_6

AN_7

Analog input

ANEX1

External op-amp

ANEX0

Resistor ladder

Bits APS1 and APS0 in

the AD0CON2 register

00b

Comparator

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