| 摘要 |
A dual-flash analog-to-digital converter comprises a first quantizer (20) for quantizing an analog input in accordance with coarse amplitude levels and outputting a more significant bits signal (24) and a remainder analog signal (32); a second quantizer (34) for quantizing the remainder signal in accordance with fine amplitude levels to output a less significant bits signal (36); and digital corrective logic (38) which receives both digital signals and corrects carry errors in the quantization. An analog method of diagnosing errors in the operation of such circuit calls for applying the remainder signal (32) to a pair of comparators (45,46) having thresholds set at upper and lower ends of the normal quantization range of second quantizer (34). The output of the comparators is passed through an OR gate (48), a low pass filter (52,54) and another comparator (56) to provide an output indicator signal (58) when the remainder signal chronically falls outside of a predetermined range set by the threshold of comparator (56). Such method can be carried out digitally by modifying the digital corrective logic (38) to provide an additional output bit to indicate whether the second quantization is within or outside a normal quantization range. The output of the first quantizer (20) is monitored by the digital corrective logic (38) to provide a second additional bit indicating high analog input levels and to digitally apply video clipping to the output of the corrective logic. |
