7906 datasheet(310/531 Pages) RENESAS

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A-D CONVERTER

7906 Group User’s Manual Rev.2.0

12-15

12.4 Absolute accuracy and Differential non-linearity error

Fig. 12.4.1 Absolute accuracy of A-D converter (10-bit resolution mode)

12.4 Absolute accuracy and Differential non-linearity error

The A-D converter’s accuracy is described below. Refer to section “Appendix 10.4 A-D converter standard

characteristics,” also.

12.4.1 Absolute accuracy

The absolute accuracy is the difference expressed in the LSB between the actual A-D conversion result

and the output code of an A-D converter with ideal characteristics. (See Figure 12.4.1 for more details.)

The analog input voltage at measurement of the absolute accuracy is assumed to be the mid point of the

analog input voltage width that outputs the same output code from an A-D converter with ideal characteristics.

For example, in the case of the 10-bit resolution mode, when VREF = 5.12 V, 1 LSB width is 5 mV, and 0

mV, 5 mV, 10 mV, 15 mV, 20 mV, ... are selected as the analog input voltages.

The absolute accuracy = ±3 LSB indicates that when the analog input voltage is 25 mV, the output code

expected from an ideal A-D conversion characteristics is “00516,” but the actual A-D conversion result is

between “00216” to “00816.”

The absolute accuracy includes the zero error and the full-scale error.

The absolute accuracy degrades when VREF is lowered. Any of the output codes for analog input voltages

in the range from VREF to Vcc is “3FF16.”

00016

00116

00216

00316

00416

00516

00616

1520

253035

4045

5055

00716

00816

00916

00A16

00B16

+3 LSB

–3 LSB

Ideal A-D conversion

characteristics

Analog input voltage (mV)

Output code

(A-D conversion result)

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