This document describes the features and characteristics of Analog Devices' AD1555/AD1556 products. The product is a 24-bit ADC with a low noise PGA and digital filter. Its features include a large dynamic range, low input noise and distortion, and high jitter tolerance.
The AD1555 is a complete sigma‑delta modulator with a programmable gain front‑end, designed for low‑frequency, high‑dynamic‑range measurement applications. When paired with the AD1556 digital filter/decimator, it forms a high‑performance 24‑bit ADC. The device features a fourth‑order modulator, low input noise, low distortion, and very high jitter tolerance, eliminating the need for an external antialias filter.
The AD1556 provides FIR digital filtering and decimation, low‑power standby operation (70 pW), and a reference‑design evaluation board with software. The handbook includes functional block diagrams, detailed specifications, timing diagrams, absolute maximum ratings, ordering guide, and mechanical dimensions for both the 28‑lead PLCC (AD1555) and 44‑lead MQFP (AD1556) packages.
| Dynamic Range (Gain 1, 1 ms) | 120 dB typical |
|---|---|
| Power Dissipation (Typical) | 77 mW |
| Standby Power (AD1556) | 70 pW |
| Programmable Gain Settings | 1, 2.5, 8.5, 34, 128 |
| Input Range | +2.25 V |
| Sampling Rate | 256 kSPS |
The AD1555 achieves a typical dynamic range of 120 dB at a 1 ms integration time.
The AD1556 consumes only 70 pW when in standby mode.
The devices offer gain settings of 1, 2.5, 8.5, 34, and 128.
Recommended supply voltages are 4.75 V to 5.25 V for both analog and digital supplies.