GM0936TQ

The GM0936TQ contains A/D and D/A conversion functions integrated on a single chip, and utilizes the sigma-delta modulation technique to achieve high resolution data conversion and low power consumption. The GM0936TQ is an ideal analog front end device for high performance voice-band communication systems. Cellular telephone systems are targeted in particular; however, these integrated circuits can function in other systems including digital audio, telecommunications, and data acquisition.

The transmit section is designed to interface directly with an electret microphone element. One of two microphone input signals, MICIN and EXTMIC, is selected by MICSEL. If MICSEL is floated or Low, then MICIN is selected, and if MICSEL is high, then EXTMIC is selected. The microphone input signal (MICIN and EXTMIC) is buffered, first-order low-pass filtered, and amplified with provision for setting the amplifier gain to accommodate a range of signal input levels. The amplified signal is 1bitmodulated by second-order sigma-delta modulator. The modulated signal is then applied to the input of high-performance FIR-type digital decimation filters with frequency response equalization. Theresulting data is then clocked out of DOUT as a serial data stream.

The receive section takes a frame of sereal data on DIN and converts it to analog through highperformance FIR-type digital interpolation filter together with frequency response equalization, second-order digital sigma-delta modulator, and analog reconstruction filters.

On-chip voltage reference ensures a highly integrated solution and all internal voltage references are generated. An internal reference voltage, VMID, is used to develop the midlevel virtual ground for all the amplifier circuits and the microphone bias circuit.Another reference voltage, MICBIAS, can supply bias current for the microphone.

Serial DSP interfaces for transmit and receive paths support directly industry standard DSP processors. The GM0936TQ devices are characterized for operation from -20 to 70.