38K2 datasheet(146/358 Pages) RENESAS

146 / 358 page

NOTES ON PROGRAMMING

Rev.2.00

Oct 15, 2006

page 127 of 130

38K2 Group

REJ09B0338-0200

HARDWARE

Definition of A/D Conversion Accuracy

The A/D conversion accuracy is defined below (refer to Figure

167).

•Relative accuracy

➀ Zero transition voltage (VOT)

This means an analog input voltage when the actual A/D con-

version output data changes from “0” to “1.”

➁ Full-scale transition voltage (VFST)

This means an analog input voltage when the actual A/D con-

version output data changes from “1023” to “1022.”

➂ Non-linearity error

This means a deviation from the line between VOT and VFST of

a converted value between VOT and VFST.

➃ Differential non-linearity error

This means a deviation from the input potential difference re-

quired to change a converted value between VOT and VFST by 1

LSB of the 1 LSB at the relative accuracy.

•Absolute accuracy

This means a deviation from the ideal characteristics between 0 to

VREF of actual A/D conversion characteristics.

VREF

1024

Vn: Analog input voltage when the output data changes from “n” to “n + 1” (n = 0 to 1022)

• 1 LSB at relative accuracy

→

(V)

• 1 LSB at absolute accuracy

→

(V)

VFST – VOT

1022

Analog voltage

VREF

V1022

Zero transition voltage (V0T)

Full-scale transition voltage (VFST)

Non-linearity error=

Actual A/D conversion

characteristics

Vn+1

n+1

1022

1023

Ideal line of A/D

conversion between

V0 to V1022

Output data

a: 1LSB at relative accuracy

b: Vn+1-Vn

c: Difference between

the ideal Vn and actual Vn

Differential non-linearity error= b-a

[LSB]

a [

LSB]

Fig. 167 Definition of A/D conversion accuracy

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