MB90F482BPMC datasheet(111/124 Pages) FUJITSU

111 / 124 page

MB90480B/485B Series

DS07-13722-11E

111

• About the external impedance of the analog input and its sampling time

• A/D converter with sample and hold circuit. If the external impedance is too high to keep sufficient sampling

time, the analog voltage charged to the internal sample and hold capacitor is insufficient, adversely affecting

A/D conversion precision.

• To satisfy the A/D conversion precision standard, consider the relationship between the external impedance

and minimum sampling time and either adjust the register value and operating frequency or decrease the

external impedance so that the sampling time is longer than the minimum value.

• If the sampling time cannot be sufficient, connect a capacitor of about 0.1

μF to the analog input pin.

• About errors

As |AVRH

− AVSS| becomes smaller, values of relative errors grow larger.

Note : Concerning sampling time, and compare time when 3.6 V

≥ AVCC ≥ 2.7 V, then

Sampling time : 1.92

μs, compare time : 1.1 μs

Settings should ensure that actual values do not go below these values due to operating frequency changes.

During sampling : ON

Analog input

Comparator

Note: The values are reference values.

• Analog input equivalent circuit

MB90487B

2.5 k

Ω (Max) 31.0 pF (Max)

MB90F481B/F482B 1.9 k

Ω (Max) 25.0 pF (Max)

MB90F488B/F489B 1.9 k

Ω (Max) 25.0 pF (Max)

MB90F481B/F482B

MB90F488B/F489B

100

MB90487B/

MB90483C

MB90F481B/F482B

MB90F488B/F489B

0123456

MB90487B/

MB90483C

(External impedance

= 0 kΩ to 100 kΩ)

(External impedance

= 0 kΩ to 20 kΩ)

Minimum sampling time [

μs]

Minimum sampling time [

μs]

• The relationship between external impedance and minimum sampling time

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