Analog Devices Inc. AD7865AS-1

Overview

AD7865AS-1 from Analog Devices is a four-channel, simultaneous-sampling, 14-bit analog-to-digital converter with 2.4 µs conversion time per channel, ±5 V/±10 V input ranges, and integrated track/hold amplifiers. It operates from a single 5 V supply, delivers 77 dB SNR at 100 kHz input, and supports high-speed parallel interfacing to microcontrollers and DSPs in motor control and power monitoring systems.

For engineers reviewing the AD7865AS-1 datasheet, AD7865AS-1 pinout, AD7865AS-1 application, or AD7865AS-1 equivalent, key selection considerations include simultaneous sampling integrity, aperture delay matching (≤4 ns), bipolar input range support, 14-bit resolution with ±2 LSB INL, and PQFP-44 packaging for industrial signal acquisition.

Technical Context

The AD7865AS-1 implements four independent track/hold amplifiers feeding a shared 14-bit successive approximation ADC core, enabling true simultaneous sampling across all channels while preserving phase relationships. Its internal 2.5 V reference, laser-trimmed oscillator, and hardware/software channel selection logic allow flexible sequencing without external timing components.

Conversion is initiated by a rising edge on CONVST, which latches channel selection (via SL1–SL4 pins or channel select register), places all track/holds into hold mode, and starts the 2.4 µs conversion sequence. BUSY remains high until all selected channels complete conversion; EOC pulses low after each individual channel's result is ready.

Key Specifications

Pinout & Package

The AD7865AS-1 is housed in a 44-lead Plastic Quad Flatpack (PQFP), measuring 10 mm × 10 mm with 0.8 mm lead pitch. The package provides dedicated analog/digital ground separation, isolated reference and drive voltage pins, and 14-bit bidirectional data bus capability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar simultaneous-sampling ADC applications.

Compared with AD7865AS-1, AD7656ASTZ trades parallel interface and 4-channel flexibility for higher resolution and channel count, while ADS8588HIPM adds two more channels and 16-bit precision but removes the integrated reference-both require layout and firmware changes due to differing pinouts and interface protocols.

Availability

AD7865AS-1 is available at Aetrix Electronics and suitable for AC motor control, uninterruptible power supplies, and industrial power metering requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7865AS-1 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 is a global semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control.

The AD7865 product line delivers simultaneous-sampling ADCs optimized for industrial automation, energy infrastructure, and real-time control systems where phase-coherent multi-channel acquisition is mandatory.

FAQ

What input voltage ranges does the AD7865AS-1 support?

The AD7865AS-1 supports bipolar input ranges of ±5 V and ±10 V, as specified in its ordering guide and electrical characteristics table. These ranges are factory-configured for the -1 variant and do not require external resistor networks or range-switching circuitry. The device maintains full 14-bit performance and ±2 LSB INL across both ranges at temperatures from –40°C to +85°C. Input overvoltage protection extends to ±18 V for the ±10 V range, safeguarding against transient events in industrial environments.

How does the AD7865AS-1 achieve simultaneous sampling across four channels?

The AD7865AS-1 achieves true simultaneous sampling using four independent, matched track/hold amplifiers-one per analog input pair (VIN1A/B through VIN4A/B). On the rising edge of the CONVST signal, all four amplifiers switch from track to hold mode at the exact same instant, freezing the analog input voltages concurrently. This preserves phase relationships between channels, enabling accurate vector calculations in motor control and power quality analysis. Aperture delay matching is guaranteed ≤4 ns, ensuring sub-degree phase error at 50/60 Hz.

What is the role of the H/S SEL pin on the AD7865AS-1?

The H/S SEL pin on the AD7865AS-1 selects between hardware-based and software-based channel sequencing. When pulled low, SL1–SL4 pins directly configure the enabled channels; when pulled high, the channel select register (programmed via DB0–DB3 during a write cycle) determines the conversion sequence. This dual-mode flexibility allows the AD7865AS-1 to integrate seamlessly into both fixed-function systems (using hardware pins) and programmable platforms (using register writes), without requiring changes to the AD7865AS-1's internal logic or timing behavior.

Does the AD7865AS-1 include an internal voltage reference?

Yes, the AD7865AS-1 integrates a 2.5 V ±20 mV internal reference accessible via the VREF pin. This reference is used by default for ADC conversions and exhibits a temperature coefficient of 25 ppm/°C typical. The VREF pin also accepts an external 2.5 V ±5% reference source, allowing system designers to substitute a higher-precision or lower-drift reference when metrology-grade accuracy is required. A 0.1 µF decoupling capacitor is mandatory between VREF and AGND to maintain stability and noise performance.

What is the maximum throughput rate of the AD7865AS-1 when converting all four channels?

The AD7865AS-1 achieves a maximum throughput rate of 100 kSPS when converting all four channels simultaneously. This is calculated from its 2.4 µs per-channel conversion time multiplied by four channels (9.6 µs total sequence time), yielding ~104 kSPS in theory; however, the datasheet specifies 100 kSPS as the guaranteed maximum under full-spec conditions including timing margins, bus access overhead, and temperature extremes. For single-channel operation, the AD7865AS-1 reaches 350 kSPS, leveraging its ability to skip unused channels in the conversion sequence.