Analog Devices Inc. AD7865AS-2

Overview

AD7865AS-2 from Analog Devices is a four-channel, simultaneous-sampling, 14-bit analog-to-digital converter (ADC) with unipolar input ranges of 0 V to 2.5 V or 0 V to 5 V, 2.4 µs conversion time per channel, ±2 LSB relative accuracy, and operation from a single 5 V supply. It integrates four track/hold amplifiers, internal 2.5 V reference, and high-speed parallel interface-designed for real-time motor control and power monitoring systems requiring phase-coherent multichannel acquisition.

For engineers reviewing the AD7865AS-2 datasheet, AD7865AS-2 pinout, AD7865AS-2 application, or AD7865AS-2 equivalent, key selection considerations include its straight-binary output coding, 100 kSPS full-channel throughput, aperture delay matching ≤4 ns, 76 dB SNR (min) at full temperature range, and PQFP-44 package compatibility with industrial embedded signal acquisition designs.

Technical Context

The AD7865AS-2 implements successive approximation architecture with four independent track/hold amplifiers enabling true simultaneous sampling across all channels. Its internal clock oscillator eliminates external timing components, while hardware/software channel selection (via SLx pins or DB0–DB3 register) supports flexible subset conversion sequencing.

It features dedicated analog and digital ground planes (AGND/DGND), separate AVDD/DVDD supplies tied externally, and VDRIVE pin supporting 3 V or 5 V output driver operation-enabling direct interfacing to both 3 V microcontrollers and 5 V DSPs without level-shifting circuitry.

Key Specifications

Pinout & Package

AD7865AS-2 is housed in a 44-lead Plastic Quad Flatpack (PQFP), 10 mm × 10 mm body, 0.8 mm lead pitch, with exposed thermal pad (S-44 package option). Pin 1 identifier located at top-left corner (top view).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7865AS-2, AD7656ASTZ offers higher resolution but lacks native 0–5 V support, while ADS8588SIPM adds channels and maintains unipolar range but sacrifices the low-latency parallel interface critical for real-time control loops.

Availability

AD7865AS-2 is available at Aetrix Electronics and suitable for AC motor control, industrial power metering, and uninterruptible power supplies requiring stable component supply across extended product lifecycles.

Supply support for AD7865AS-2 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 leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA, serving industrial, automotive, communications, and healthcare markets since 1965.

The AD7865 product line delivers simultaneous-sampling multichannel ADCs optimized for real-time closed-loop control and power quality monitoring - emphasizing phase fidelity, low power, and robust industrial interface compatibility.

FAQ

What input voltage ranges does the AD7865AS-2 support?

The AD7865AS-2 supports two unipolar analog input ranges: 0 V to 2.5 V and 0 V to 5 V. It does not support bipolar ranges like ±2.5 V or ±5 V - those are handled by the AD7865AS-1 and AD7865AS-3 variants. Input current is specified at 10 µA max for the 0–2.5 V range and 1 mA max for the 0–5 V range, ensuring minimal loading on precision sensor circuits. This makes the AD7865AS-2 ideal for interfacing directly with 3.3 V or 5 V-output transducers without external amplification or level shifting.

How does the AD7865AS-2 achieve simultaneous sampling across four channels?

The AD7865AS-2 achieves true simultaneous sampling using four independent track/hold amplifiers, one per analog input pair (VIN1A/VIN1B through VIN4A/VIN4B). On the rising edge of the CONVST signal, all four track/holds switch from track to hold mode at the same instant, freezing the input voltages with ≤4 ns aperture delay matching. This preserves phase relationships between acquired signals - a requirement verified in the AD7865AS-2's datasheet specifications and essential for applications like motor current vector analysis. The subsequent conversion proceeds sequentially across the selected channels.

What is the output coding format of the AD7865AS-2?

The AD7865AS-2 uses straight (natural) binary output coding, unlike the two's complement format used by the AD7865AS-1 and AD7865AS-3 variants. For example, a full-scale 0–5 V input produces a digital output of 0x3FFF (16383 decimal), while 0 V yields 0x0000. This simplifies firmware interpretation in unipolar systems and avoids sign-extension logic in microcontroller drivers. The coding format is hardwired per variant and cannot be changed in-circuit - confirming that AD7865AS-2 is specifically intended for unipolar signal chains.

Can the AD7865AS-2 interface directly with a 3 V microcontroller?

Yes, the AD7865AS-2 can interface directly with a 3 V microcontroller using its VDRIVE pin. When VDRIVE is supplied with 3 V ±10%, the DB0–DB13 data outputs, BUSY, EOC, and FRSTDATA signals operate at 3 V logic levels - meeting standard TTL/CMOS thresholds for 3 V systems. The internal AVDD and DVDD supplies remain at 5 V, isolating analog performance from digital I/O voltage. This dual-supply flexibility eliminates level translators in mixed-voltage designs, and is explicitly validated in the AD7865AS-2's timing characteristics table for VDRIVE = 3 V conditions.

What is the maximum throughput rate when using all four channels of the AD7865AS-2?

The maximum throughput rate for all four channels of the AD7865AS-2 is 100 kSPS (kilo-samples per second), meaning the complete four-channel conversion sequence finishes every 10 µs. This is derived from the 2.4 µs per-channel conversion time multiplied by four channels, plus overhead for bus arbitration and settling. At this rate, the AD7865AS-2 maintains full 14-bit linearity and 76 dB SNR performance across the –40°C to +85°C temperature range. Throughput drops to 350 kSPS when reading only a single channel - a feature enabled by configurable channel selection via SL1–SL4 pins or the channel select register.