Successive approximation type ad converter and test method thereof

First Embodiment

[0033]Referring to FIGS. 2 to 8, the successive approximation type AD converter according to a first embodiment of the present invention will be described.

(Configuration)

[0034]FIG. 2 is a diagram showing a configuration of the successive approximation type AD converter according to the present invention. The successive approximation type AD converter according to the present invention includes a DA section 10, a comparator section 20, and a successive approximation section 30. The DA section 10 and the comparator section 20 may be collectively referred to as a conversion comparison section. The DA section 10 in the present embodiment has a C-R type DAC, and outputs a local analog signal 101 corresponding to digital data supplied from the successive approximation section 30. The comparator section 20 compares an analog signal 100 supplied to an analog input terminal (hereinafter, to be referred to as an input analog signal 100) with an analog signal corresponding to the

Second Embodiment

[0072]In the first embodiment, the 12-bit successive approximation type AD converter is tested by the test to the 3-bit AD converter only using the DA converter by the R string section 11, and the test to the 9-bit AD converter only using the DA converter by the C array section 12 (the electric charge distribution type DAC). That is, in the first embodiment, the resolution of the AD converter to be tested is reduced by testing the successive approximation type AD converter only using one of two stages of the DAC (either one of portions corresponding to the upper bits and the lower bits).

[0073]Meanwhile, in a second embodiment, the test of the conversion precision is carried out by using the AD converter only using either one of the two stages of the DAC (for example, the upper bits) and the AD converter in which the resolution in one of the two stages of the DAC (for example, the upper bits) is lowered.

[0074]Referring to FIGS. 9 to 11, the successive approximation type