| 摘要 |
<p>An integrated-circuit, continuous-time, sigma-delta ADC has a single-ended input Vin, a reference input Vref, and an Earth connection. The input signal is converted to a current by resistor Rin and balanced by an OTA RC integrator against a switched feedback current flowing through Rref and an offset current flowing through Roffset. The ADC is linear over a large input range and occupies a small IC area. The full-scale and mid-scale input voltages, which depend on the Rin/Rref and Roffset/Rref ratios, may be adjusted under processor control by varying the resistors Rin and Roffset. A clocked comparator CMP is connected to the integrator output and its output D controls the switch. The comparator and the OTA receive a common reference input of Vref/2. The comparator output may be fed to a counter which provides a digital output DOUT representing the proportion of cycles for which D is high.</p> |
