A mixed-mode single-chip motor-drive-specific microcontroller with a 12-bit 125/KS/s ADC

A mixed-mode single-chip motor-driver-specific 32-bit microcontroller was designed and implemented by using a 0.6 /spl mu/m triple-metal CMOS process. The microcontroller chip includes the SPARC-V7 processor as the main CPU, a single-precision floating-point unit, a memory controller, and all the peripheral devices for an AC induction motor drive, including a 12-bit 125 KS/s ADC. The ADC uses a successive approximation algorithm and a folded-array resistor-string DAC to enhance noise immunity and monotonicity. The chip size is 12.1/spl times/11.7 mm/sup 2/, the number of transistors used is around 882,000, and the power consumption is 2.6 W at a supply voltage of 5 V and a clock frequency of 33.3 MHz. The substrate current picked up by a guard ring surrounding the ADC block was measured at different clock frequencies of digital circuits. The correlation between SFDR of ADC and the substrate noise current was demonstrated.