Fast readout method and switched capacitor array for waveform digitizing

摘要

The present invention represents a technique to reduce the readout time of switched capacitor array (SCA) circuitries. A possible implementation is a SCA chip capable of sampling 12 differential input channels at a sampling speed of 10 MSPS to 5 GSPS. The analog waveform can be stored in 1024 sampling cells per channel, and can be read out after sampling via a shift register clocked at 33 MHz for external digitization. The write signal for the sampling cells is generated by a chain of inverters (domino principle) generated on the chip. The domino wave is running continuously until stopped by a trigger. A read shift register clocks the contents of the sampling cells either to a multiplexed or to individual outputs, where it can be digitized with an external ADC. It is possible to read out only a part of the waveform for reducing the digitization time. The high channel density, high analog bandwidth of 450 MHz, and low noise of 0.35 mV (after offset calibration) makes this chip ideally suited for low power, high speed, high precision waveform digitizing. Fabricated on an advanced CMOS process in a radiation hard design, the present chip is available in a 64-lead low profile quad flat pack (LQFP) and a 64-pin quad flat non-leaded package (QFN).