Analog Devices Inc. AD977ARSZ

Overview

AD977ARSZ from Analog Devices is a 16-bit, 100 kSPS successive-approximation analog-to-digital converter (ADC) operating from a single 5 V supply. It features factory-calibrated linearity, on-chip 2.5 V reference, high-speed serial interface, and supports ±10 V, ±5 V, ±3.3 V bipolar and 0 V–10 V/0 V–5 V/0 V–4 V unipolar input ranges - deployed in precision industrial data acquisition and process control systems.

For engineers reviewing the AD977ARSZ datasheet, AD977ARSZ pinout, AD977ARSZ application, or AD977ARSZ equivalent, key selection considerations include throughput rate (100 kSPS), INL (±3 LSB), power-down mode (50 µW), serial data format (two's complement or straight binary), and compatibility with internal or external DATACLK timing control.

Technical Context

The AD977ARSZ implements a switched-capacitor SAR architecture with integrated reference buffer and serial output register. Its conversion control relies on dual digital inputs (R/C and CS), supporting both internal clock generation and external DATACLK synchronization via the EXT/INT pin.

It provides configurable data coding (SB/BTC pin), frame synchronization (SYNC output), and daisy-chain capability (TAG input) for multi-channel systems. Aperture delay is fixed at 40 ns, and transient response to full-scale step is 2 µs across all grades.

Key Specifications

Pinout & Package

AD977ARSZ is housed in a 20-lead 0.15 mm pitch "Skinny SOIC" (SOIC_N) package per JEDEC MS-013AC, with exposed pad not present and moisture sensitivity level (MSL) rated at 1. Pin functions are validated per Analog Devices Rev. E datasheet Figures 3 and Table 6.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit SAR ADC applications.

Compared with AD977ARSZ, AD977AARSZ offers doubled throughput but requires revised timing margins and higher REF drive capability, while LTC2311-16 trades internal integration for superior AC specs and flexibility in reference and interface design.

Availability

AD977ARSZ is available at Aetrix Electronics and suitable for industrial process monitoring, automated test equipment, and programmable logic controller I/O modules requiring stable component supply and long-term obsolescence management.

Supply support for AD977ARSZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and DSP technologies, serving industrial, automotive, communications, and healthcare markets since 1965.

The AD977 product line delivers precision, low-power, single-supply 16-bit SAR ADCs optimized for space-constrained, thermally demanding industrial data acquisition where calibration stability and input flexibility are critical.

FAQ

What is the maximum sampling rate supported by the AD977ARSZ?

The AD977ARSZ supports a maximum throughput rate of 100 kSPS, corresponding to a complete conversion cycle time of 10 µs. This is specified across all grade options (A/B/C) and operating conditions (–40°C to +85°C). The AD977ARSZ achieves this rate using its internal switched-capacitor SAR architecture and on-chip clock generator. Note that actual system throughput may be lower when using external DATACLK in discontinuous mode due to setup/hold timing constraints.

Does the AD977ARSZ require an external reference voltage?

No, the AD977ARSZ does not require an external reference voltage. It integrates a precision 2.5 V internal reference (2.48 V to 2.52 V) that can be used directly by connecting the REF pin to the internal reference node and bypassing CAP to AGND2 with a 2.2 µF tantalum capacitor. An external reference between 2.3 V and 2.7 V may be applied to REF if higher accuracy or temperature stability is needed, but it is optional - the AD977ARSZ operates fully functional with its internal reference.

How does the power-down mode function on the AD977ARSZ?

The AD977ARSZ enters ultra-low-power mode when the PWRD pin is driven HIGH, reducing supply current to 50 µW while preserving the last conversion result in the internal shift register. In this state, analog conversion is inhibited, but the digital interface remains accessible for reading prior data. Recovery to full accuracy after exiting power-down takes 1 ms when a 2.2 µF capacitor is connected to CAP. This feature enables duty-cycled operation in battery-powered or thermally sensitive applications without losing data integrity.

Can the AD977ARSZ interface directly with a microcontroller SPI port?

The AD977ARSZ supports serial data transfer but is not SPI-compatible by protocol. Its DATA, DATACLK, and SYNC signals operate in a proprietary timing scheme defined by R/C and CS control - not standard SPI CPOL/CPHA modes. While many microcontrollers can bit-bang the interface using GPIO, dedicated SPI hardware peripherals cannot drive it without custom timing logic. The AD977ARSZ requires precise setup/hold times (e.g., t10 = 50 ns, t11 = 20 ns) and supports both internal clock (EXT/INT = LOW) and external clock (EXT/INT = HIGH) configurations.

What are the valid analog input voltage ranges for the AD977ARSZ?

The AD977ARSZ supports six factory-configured input ranges: bipolar ±10 V, ±5 V, ±3.3 V and unipolar 0 V–10 V, 0 V–5 V, and 0 V–4 V. These are selected by external resistor networks on R1IN/R2IN/R3IN per Table 8 in the datasheet - no internal register programming is required. Input impedance varies by range (e.g., ~100 kΩ for ±10 V), and the device tolerates up to ±25 V on analog inputs without damage. Full-scale accuracy is guaranteed only within the selected range; exceeding it causes clipping but no latch-up.