Fully-integrated 5 V CMOS system for a 20 M sample/s sampling oscilloscope

The implementation of an inexpensive small sampling oscilloscope in a probe requires integration of all relevant system functions on one single 5 V chip. This chip is also useful for many other applications, e.g., PC measurement boards with more than one channel. The function of the IC is as follows. After loading the control registers for time base, trigger level, trigger mode and input voltage range, recording of the input voltage is started by the trigger pulse and completed when the 6 b data from the A/D converter is written to the embedded SRAM 128 times. Then a microcontroller reads the stored data that is processed and sent to the LCD and optionally to a serial PC port. To save power, current-consuming analog circuitry is only activated during the short data recording time. The chip uses a 1.2 /spl mu/m CMOS technology that includes implanted poly resistors, poly-poly capacitors and depletion FETs with Vth=1.8 V for analog applications. The chip is packaged in a PLCC44.