AD7722

a FEATURES 16-Bit Sigma-Delta ADC 64 ؋ Oversampling Ratio Up to 220 kSPS Output Word Rate Low-Pass, Linear Phase Digital Filter Inherently Monotonic On-Chip 2.5 V Voltage Reference Single Supply +5 V High Speed Parallel or Serial Interface 16-Bit, 195 kSPS CMOS, Sigma-Delta ADC AD7722 FUNCTIONAL BLOCK DIAGRAM DGND DVDD AGND AVDD REF1 AD7722 2.5V REFERENCE REF2 VIN(+) VIN(–) 16-BIT A/D CONVERTER Σ∆ MODULATOR FIR FILTER P/S CAL RESET SYNC CS DVAL/RD CFMT/DRDY DB0 DB1 DB2 CONTROL LOGIC CLOCK CIRCUITRY XTAL CLKIN UNI DB15 DB14 DB13 DB12 DB11 DB10 DB9/FSO GENERAL DESCRIPTION The AD7722 is a complete low power, 16-bit, sigma-delta ADC. The part operates from a +5 V supply and accepts a differential input voltage range of 0 V to +2.5 V or ± 1.25 V centered around a common-mode bias. The AD7722 provides 16-bit performance for input bandwidths up to 90.625 kHz. The part provides data at an output word rate of 195.3 kHz. The analog input is continuously sampled by an analog modulator eliminating the need for external sample-and-hold circuitry. The modulator output is processed by two Finite Impulse Response (FIR) digital filters in series. The on-chip filtering reduces the external antialias requirements to first order, in most cases. The group delay for the filter is 215.5 µs, while the settling time for a step input is 431 µs. The sample rate, filter corner frequency, and output word rate are set by an external clock that is nominally 12.5 MHz. Use of a single bit DAC in t...