7540 datasheet(270/366 Pages) RENESAS

270 / 366 page

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REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

APPENDIX

7540 Group

3.2 Typical characteristics

(11) A/D conversion typical characteristics example

➀ Definition of A/D conversion accuracy

The A/D conversion accuracy is defined below (refer to Fig. 3.2.40).

qRelative accuracy

• Zero transition voltage (VOT)

This means an analog input voltage when the actual A/D conversion output data changes from

“0” to “1.”

• Full-scale transition voltage (VFST)

This means an analog input voltage when the actual A/D conversion output data changes from

“1023” to “1022.”

• Non-linearity error

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

VFST.

• Differential non-linearity error

This means a deviation from the input potential difference required to change a converted value

between VOT and VFST by 1 LSB of the 1 LSB at the relative accuracy.

qAbsolute accuracy

This means a deviation from the ideal characteristics between 0 to VREF of actual A/D conversion

characteristics.

VREF

1024

Fig. 3.2.40 Definition of A/D conversion accuracy

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

a [LSB]

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