A/D converter with noise elimination function

Details A/D converter with noise elimination function A/D converter with noise elimination function

2002-12-23

2003-10-28

Tokar, Michael (Department: 2819)

Coded data generation or conversion

Analog to or from digital conversion

Analog to digital conversion

C341S118000, C341S120000

Reexamination Certificate

active

06639540

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an A/D converter with noise elimination function in a semiconductor device.
2. Description of Related Art
FIG. 10
is a block diagram showing a configuration of a conventional A/D converter. In
FIG. 10
, the reference numeral
1
designates an A/D conversion reference voltage Vref;
2
designates a noise filtering module for removing noise from the A/D conversion reference voltage Vref
1
;
3
designates an A/D conversion module for converting an analog input Ain to a digital output with reference to the A/D conversion reference voltage Vref
1
; and
4
designates an A/D controller for controlling the A/D conversion module
3
.
FIGS. 11A and 11B
are tables illustrating a setting method of the A/D conversion reference voltage Vref of the A/D converter.
Next, the operation of the conventional A/D converter will be described.
In
FIG. 10
, the noise filtering module
2
removes the noise of the A/D conversion reference voltage Vref
1
, and supplies its output to the A/D conversion module
3
.
FIG. 11A
gives expressions of the relationships between the A/D conversion reference voltage Vref
1
and the reference voltage VREF in the A/D conversion module
3
; and
FIG. 11B
illustrates the variations in the content of the A/D conversion register in the A/D conversion module
3
during the A/D conversion.
When the A/D conversion is started, the A/D conversion register is placed at “0 . . . 0”. Subsequently, the most significant bit of the A/D conversion register is placed at “1”, and the A/D conversion reference voltage Vref
1
is supplied to the comparator in the A/D conversion module
3
, which compares the A/D conversion reference voltage Vref
1
with the analog input Ain. If the compared result is Vref<Ain, the most significant bit of the A/D conversion register is maintained at “1”, whereas if Vref>Ain, the most significant bit of the A/D conversion register is placed at “0”.
Carrying out the foregoing operation down to the least significant bit of the A/D conversion register, the A/D conversion module
3
stores into the A/D conversion register the digital value obtained by converting the analog input Ain.
With the foregoing configuration, the conventional A/D converter cannot obtain accurate A/D conversion data when the A/D conversion reference voltage Vref
1
includes noise. Thus, it includes the noise filtering module
2
for removing noise from the A/D conversion reference voltage Vref
1
so as to supply the noise reduced A/D conversion reference voltage Vref
1
to the A/D conversion module
3
.
However, the conventional A/D converter has a problem of being unable to obtain the accurate A/D conversion data if the A/D conversion reference voltage Vref
1
includes noise that cannot be removed by the noise filtering module
2
. In addition, it has a problem of increasing the circuit scale because of the noise filtering module
2
.
SUMMARY OF THE INVENTION
The present invention is implemented to solve the foregoing problems. It is therefore an object of the present invention to provide an A/D converter capable of obtaining reliable A/D conversion data without increasing the circuit scale so much even if the A/D conversion reference voltage includes noise.
According to a first aspect of the present invention, there is provided an A/D converter including: an A/D operation controller for generating a bit-shift signal in response to a detection signal fed from a detector; and an A/D conversion module for carrying out A/D conversion with reference to an A/D conversion reference voltage, for discarding an A/D conversion resultant bit affected by noise in response to the bit-shift signal, for holding remaining A/D conversion resultant bits, and for restarting the A/D conversion from the discarded A/D conversion resultant bit after the noise becomes negligible. It offers an advantage of being able to improve the reliability of the A/D conversion data by discarding the A/D conversion resultant bit affected by sudden noise or crosstalk noise during the USB communication.
According to a second aspect of the present invention, there is provided an A/D converter including: an A/D conversion module for generating A/D conversion resultant data by carrying out A/D conversion of an analog input signal with reference to an A/D conversion reference voltage; and an A/D operation controller for deciding an A/D conversion resultant bit affected by noise in response to the detection signal and to the A/D conversion resultant data, and for outputting reliability information together with the A/D conversion resultant data. It can learn the reliability of the A/D conversion resultant data affected by the sudden noise or crosstalk noise during the USB communication. As a result, it offers an advantage of being able to improve the reliability of the A/D conversion data by discarding the A/D conversion resultant data with the reliability less than a certain level.


REFERENCES:
patent: 5307066 (1994-04-01), Kobayashi et al.
patent: 5373293 (1994-12-01), Hirata
patent: 5640161 (1997-06-01), Johnson et al.
patent: 5663729 (1997-09-01), Wada et al.
patent: 2001-111422 (2001-04-01), None

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