| 摘要 |
<p>An analog-to-digital converter (ADC) generates an output digital value equivalent to the difference between two analog signal values. The ADC 30 receives a first analog signal level, a second analog signal level and a ramp signal. A counter 32 is operable to count in a single direction. A control stage is arranged to enable the counter 32 based on a comparison 19 of the ramp signal with the first analog signal and the second analog signal. A digital value accumulated by the counter during a period when it is enabled forms the output. The ADC can perform the conversion during a conversion cycle which has two phases, with the ramp signal being reset between the two phases.. The counter 32 can be loaded with a starting digital value representing an exposure level accumulated during a previous exposure period. Techniques are described for reducing the conversion time.</p> |
