Analog Devices Inc. AD7825BNZ

Overview

AD7825BNZ from Analog Devices is a high-speed, 4-channel, 8-bit analog-to-digital converter (ADC) with 2 MSPS throughput, 420 ns conversion time, on-chip 2.5 V reference, and parallel microprocessor interface - used in DSP front ends and mobile communication subsampling systems.

For engineers reviewing the AD7825BNZ datasheet, AD7825BNZ pinout, AD7825BNZ application, or AD7825BNZ equivalent, key selection criteria include channel count (4 single-ended), supply flexibility (3 V ±10% or 5 V ±10%), track-and-hold acquisition time (200 ns), SNR at 30 kHz (48 dB min), and automatic power-down via CONVST logic level sampling at EOC assertion.

Technical Context

The AD7825BNZ implements an 8-bit half-flash architecture: a coarse 4-bit flash stage followed by a fine 4-bit flash stage, achieving full conversion in ≤420 ns. Its track-and-hold amplifier supports full-scale input signals up to 10 MHz, enabling subsampling applications without external anti-aliasing filters.

Channel selection is performed externally via A0/A1 address inputs, independent of data bus activity; conversion initiation and power-down control share the CONVST pin, while dedicated PD pin enables explicit low-power mode entry - distinguishing it from the single-channel AD7822 and 8-channel AD7829 variants.

Key Specifications

Pinout & Package

The AD7825BNZ is housed in a 24-lead, 0.3" wide plastic dual in-line package (PDIP) with through-hole mounting and standard lead pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-channel, 8-bit, parallel-output ADC applications.

Compared with AD7825BNZ, AD7825BRZ offers identical electrical performance in a smaller footprint but higher thermal resistance, while MAX1186BCPP+ trades parallel simplicity and analog configurability for serial interface efficiency - making AD7825BNZ uniquely balanced for mixed-signal systems needing hardware channel control, on-chip reference, and adaptive power management.

Availability

AD7825BNZ is available at Aetrix Electronics and suitable for disk drive read channels, medical ultrasound beamforming, and industrial data acquisition requiring stable component supply across extended product lifecycles.

Supply support for AD7825BNZ 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 AD7822/AD7825/AD7829 family was designed specifically for high-speed, low-power, microprocessor-compatible data acquisition in DSP front ends, mobile communications, and disk drive systems - emphasizing ease of parallel interface integration and flexible analog input handling.

FAQ

What is the maximum sampling rate supported by the AD7825BNZ?

The AD7825BNZ supports a maximum throughput of 2 MSPS (2 million samples per second), with a guaranteed maximum conversion time of 420 ns. This rate is achievable across the full industrial temperature range (−40°C to +85°C) and under both 3 V ±10% and 5 V ±10% supply conditions. The timing is validated with proper setup/hold margins on CONVST, RD, and CS signals as specified in Table 2 of the AD7825BNZ datasheet Rev. C.

Does the AD7825BNZ require an external reference voltage?

No, the AD7825BNZ includes an on-chip 2.5 V reference with ±50 mV initial error and 50 ppm/°C temperature coefficient, accessible at the VREF IN/OUT pin. External reference use is optional and only recommended when higher absolute accuracy or lower drift is required. When using the internal reference, VREF IN/OUT may be left unconnected or decoupled to AGND with a 0.1 µF capacitor - no external reference circuitry is needed for standard AD7825BNZ operation.

How does channel selection work on the AD7825BNZ?

Channel selection on the AD7825BNZ is performed via two dedicated hardware address pins: A0 and A1. These pins accept static logic levels before the RD signal goes low, selecting one of four analog inputs (VIN1–VIN4) without requiring any register writes or software configuration. This hardware-based method ensures deterministic, zero-latency channel switching - a key differentiator from serial or command-driven ADCs - and is fully documented in the Pin Function Descriptions section of the AD7825BNZ datasheet.

What is the purpose of the VMID pin on the AD7825BNZ?

The VMID pin on the AD7825BNZ allows users to center the analog input voltage span anywhere between AGND and VDD - for example, shifting the default 0 V to 2.5 V (5 V supply) or 0 V to 2.0 V (3 V supply) range to −1.25 V to +1.25 V or −1.0 V to +1.0 V. This feature accommodates system-level DC offsets and relaxes input driver requirements in single-supply signal chains. When left unconnected, VMID defaults to 1.25 V (5 V) or 1.0 V (3 V), establishing the nominal input range center point.

Can the AD7825BNZ operate from a 3.3 V supply?

No, the AD7825BNZ is specified only for 3 V ±10% (2.7 V to 3.3 V) and 5 V ±10% (4.5 V to 5.5 V) operation. While 3.3 V falls within the upper limit of the 3 V range, Analog Devices' datasheet Rev. C explicitly defines "3 V ±10%" as 2.7 V to 3.3 V *for specified performance* - meaning all AC/DC parameters (e.g., SNR, INL, conversion time) are guaranteed only across that full band. Operation at exactly 3.3 V is permitted, but marginally - design margins should account for supply tolerance, load regulation, and temperature drift to ensure compliance with AD7825BNZ specifications.