MB90438LPF datasheet(49/60 Pages) FUJITSU

49 / 60 page

MB90435 Series

DS07-13727-2E

(Continued)

• Notes on Using A/D Converter

Select the output impedance value for the external circuit of analog input according to the following conditions, :

• Output impedance values of the external circuit of 15 k

Ω or lower are recommended.

• When capacitors are connected to external pins, the capacitance of several thousand times the internal

capacitor value is recommended to minimized the effect of voltage distribution between the external capacitor

and internal capacitor.

Note : When the output impedance of the external circuit is too high, the sampling period for analog voltages may

not be sufficient (sampling period

= 4.00 µs @machine clock of 16 MHz) .

•Error

The smaller the | AVRH

− AVRL |, the greater the error would become relatively.

3FF

3FE

3FD

004

003

002

001

AVRL

AVRH

AVRL

AVRH

+ 1

− 1

− 2

VNT

V (N + 1) T

VOT

VFST

{1 LSB

× (N − 1) + VOT }

Linearity error

Differential linearity error

Analog input

Actual conversion

value

(measured value)

Actual conversion

characteristics

Theoretical

characteristics

(measured value)

Theorential characteristics

Actual conversion value

(measured value)

Acturel conversion

value

Linearity error of

digital output N

[LSB]

VNT

− {1 LSB × (N − 1) + VOT}

1 LSB

[V]

VFST

− VOT

1022

1 LSB

− 1 LSB [LSB]

V (N

+ 1) T − VNT

1 LSB

Differential linearity error

of digital N

VOT : Voltage at transition of digital output from “000H” to “001H”

VFST : Voltage at transition of digital output from “3FEH” to “3FFH”

3.2 k

Ω Max.

30 pF Max.

Analog input

Comparator

• Equipment of analog input circuit model

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