Analog Devices Inc. AD7861APZ

Overview

AD7861APZ from Analog Devices is an 11-bit simultaneous-sampling analog-to-digital converter (ADC) with four-channel sample-and-hold, internal 2.5 V reference, ±2 LSB relative accuracy, and 3.2 µs per-channel conversion time at 12.5 MHz clock. It acquires stator currents in motor control systems and supports flexible channel sequencing for VIN1–VIN3 and AUX0–AUX3 inputs.

For engineers reviewing the AD7861APZ datasheet, AD7861APZ pinout, AD7861APZ application, or AD7861APZ equivalent, this device is selected for high-fidelity multichannel acquisition where phase coherence across up to four analog inputs is critical-especially in three-phase power measurement and real-time DSP-based motor control interfacing.

Technical Context

The AD7861APZ integrates a 4-channel simultaneous sample-and-hold amplifier (SHA) with 1.6 µs acquisition time and 20 ns aperture delay match, preserving inter-channel phase integrity. Its successive-approximation architecture delivers twos-complement 11-bit output with 60 dB SNR at 1 kHz input and –60 dB THD.

Channel selection is controlled via M0/M1 pins defining 2–4 channel groups (e.g., VIN2/VIN3 only or full VIN1–VIN3 + AUX), while S0/S1 configure auxiliary multiplexing among AUX0–AUX3. Conversion is initiated by CONVST and synchronized to an external 6.25–12.5 MHz clock, requiring 40 clock cycles per channel.

Key Specifications

Pinout & Package

AD7861APZ uses a 44-lead plastic leadless chip carrier (P-44A) package with exposed thermal pad. Pin layout supports dedicated analog/digital ground separation, dual VDD supplies (Pins 21 & 36), and signal-ground (SGND) isolation at Pin 35.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7861APZ, AD7865-1ARSZ offers higher resolution but less integrated reference functionality, while ADS8556IPMR expands channel count and resolution at the cost of increased design complexity and external reference dependency.

Availability

AD7861APZ is available at Aetrix Electronics and suitable for motor control feedback loops, three-phase power monitoring, and DSP-based signal processing nodes requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7861APZ 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 digital signal processing semiconductors, headquartered in Norwood, MA.

The AD7861 belongs to Analog Devices' precision data acquisition product line, engineered specifically for real-time multichannel sampling in motor control, power electronics, and industrial automation where phase-coherent analog capture is essential.

FAQ

What is the maximum clock frequency supported by the AD7861APZ?

The AD7861APZ operates with an external system clock ranging from 6.25 MHz to 12.5 MHz. At 12.5 MHz, each conversion cycle completes in 3.2 µs per channel, enabling a minimum group throughput time of 14.4 µs for four channels. Exceeding 12.5 MHz violates AC timing specifications and may cause data corruption or BUSY timing violations in the AD7861APZ.

How does the AD7861APZ handle simultaneous sampling across multiple channels?

The AD7861APZ uses a dedicated 4-channel sample-and-hold amplifier (SHA) that captures VIN1, VIN2, VIN3, and one AUX input simultaneously on the rising edge of CONVST. The SHA holds each input for 1.6 µs before sequential digitization begins, ensuring phase relationships are preserved-critical for vector control algorithms relying on synchronized current measurements in the AD7861APZ.

Can the AD7861APZ operate without an external reference voltage?

Yes-the AD7861APZ includes an internal 2.5 V ±5% reference. By connecting REFOUT to REFIN, the device achieves fully self-contained operation with no external reference required. This configuration is validated in the AD7861APZ datasheet and simplifies layout while maintaining specified DC accuracy and SNR performance.

What is the function of the D0 pin on the AD7861APZ?

D0 on the AD7861APZ is permanently tied low and serves as the least significant bit (LSB) placeholder in the 12-bit parallel data bus. The actual 11-bit twos-complement result occupies D1–D11 (D1 = LSB, D11 = MSB), left-justified to align with standard DSP data bus architectures. This design ensures seamless interfacing with ADSP-21xx processors without bit-shifting logic in the AD7861APZ.

How are auxiliary channels selected on the AD7861APZ?

Auxiliary channels AUX0–AUX3 are selected using the S0 and S1 pins: S1/S0 = 00 selects AUX0, 01 selects AUX1, 10 selects AUX2, and 11 selects AUX3. These pins must be stable for at least two clock cycles before CONVST assertion to ensure correct channel routing into the auxiliary ADC path in the AD7861APZ.