The AD1555/AD1556 is a 24-bit ∆-Σ ADC with low noise PGA featuring a fourth-order ∆-Σ modulator, large dynamic range, low input noise, low distortion, low intermodulation, very high jitter tolerance and programmable gain front end input range.
The AD1555 and AD1556 are high‑performance sigma‑delta analog‑to‑digital converters that integrate a programmable gain amplifier and a digital filter. They are intended for low‑frequency, high‑dynamic‑range measurement applications such as seismic data acquisition, chromatography, and automatic test equipment. The devices are offered in 28‑lead PLCC (AD1555) and 44‑lead MQFP (AD1556) packages and operate from –55 °C to +85 °C (B‑grade) or 0 °C to +85 °C (A‑grade).
The document provides functional block diagrams, detailed pin descriptions, timing specifications, absolute maximum ratings, ordering information, and layout recommendations to help designers achieve optimal analog and digital performance while minimizing noise coupling.
| Total Harmonic Distortion (Gain 1) | -120 dB max |
|---|---|
| Jitter Tolerance | 300 ps |
| Clock Input Frequency (CLKIN) | 0.975 – 1.075 MHz |
The clock input (CLKIN) may be between 0.975 MHz and 1.075 MHz.
AD1555 is offered in a 28‑lead PLCC (P‑28A) and AD1556 in a 44‑lead MQFP (S‑44A).