GENERAL DESCRIPTION
The AD1555 is a complete sigma-delta modulator, combined with a programmable gain amplifier intended for low frequency,high dynamic range measurement applications. The AD1555 outputs a ones-density bitstream proportional to the analog input. When used in conjunction with the AD1556 digital filter/ decimator, a high performance ADC is realized.

FEATURES
AD1555
    Fourth Order Σ-Δ Modulator
    Large Dynamic Range
        116 dB Min, 120 dB Typical @ 1 ms
        117 dB Typical @ 0.5 ms
    Low Input Noise: 80 nV rms @ 4 ms with
        Gain of 34,128
    Low Distortion: –111 dB Max, –120 dB Typical
    Low Intermodulation: 122 dB
    Sampling Rate at 256 kSPS
    Very High Jitter Tolerance
    No External Antialias Filter Required
    Programmable Gain Front End
    Input Range: ±2.25 V
    Robust Inputs
    Gain Settings: 1, 2.5, 8.5, 34, 128
    Common-Mode Rejection (DC to 1 kHz)
        93 dB Min, 101 dB Typical @ Gain of 1
    77 mW Typical Low Power Dissipation
    Standby Modes
AD1556
    FIR Digital Filter/Decimator
    Serial or Parallel Selection of Configuration
    Output Word Rates: 250 SPS to 16 kSPS
    6.2 mW Typ Low Power Dissipation
    70 mW in Standby Mode
    Reference Design and Evaluation Board with
        Software Available

APPLICATIONS
    Seismic Data Acquisition Systems
    Chromatography
    Automatic Test Equipment