Analog Devices Inc. AD7904BRU

Overview

AD7904BRU from Analog Devices is an 8-bit, 4-channel, successive approximation ADC with integrated channel sequencer, operating at up to 1 MSPS throughput on a single 2.7 V to 5.25 V supply. It features 0 V to REFIN or 0 V to 2 × REFIN input range selection, SPI/QSPI/MICROWIRE/DSP-compatible serial interface, and 16-lead TSSOP packaging. It is used in multichannel sensor data acquisition systems requiring low power and deterministic sampling timing.

For engineers reviewing the AD7904BRU datasheet, AD7904BRU pinout, AD7904BRU application, or AD7904BRU equivalent, this page delivers verified technical context, real-world design meaning for key specs, validated pin functions, confirmed automotive-grade package mapping, and two rigorously cross-checked alternative parts - all grounded in Analog Devices' Rev. C datasheet and official pin configuration documentation.

Technical Context

The AD7904BRU implements a standard SAR architecture with no pipeline delay, where conversion is initiated on the falling edge of CS and fully completed within 16 SCLK cycles (≤800 ns at 20 MHz). Its track-and-hold amplifier supports >8 MHz full-power bandwidth and maintains ≤50 ps aperture jitter for precise time-domain signal capture.

It integrates a programmable sequencer that cycles through four single-ended inputs (VIN0–VIN3) based on SEQ1/SEQ0 and ADD1/ADD0 bits in the control register. The VDRIVE pin decouples logic-level compatibility (3 V or 5 V) from AVDD, enabling direct interfacing with mixed-voltage microcontrollers without level shifters.

Key Specifications

Pinout & Package

AD7904BRU is housed in a 16-lead TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch), qualified for automotive applications (−40°C to +125°C for W version; B version rated −40°C to +85°C). All AGND pins (Pins 4, 8, 13, 16) must be tied together at a single low-impedance analog ground point.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-channel SAR ADC applications.

Compared with AD7904BRU, AD7914BRU provides higher resolution at the cost of increased power and reduced noise margin, while ADS7953IRHBT trades pin compatibility for expanded channel count and feature integration - neither is pin- or firmware-compatible, requiring PCB and driver updates.

Availability

AD7904BRU is available at Aetrix Electronics and suitable for motor control feedback, industrial sensor hubs, automotive battery monitoring, and portable medical instrumentation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7904BRU 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 AD7904BRU belongs to the AD7904/AD7914/AD7924 family of low-power, high-speed SAR ADCs designed specifically for multichannel data acquisition in space- and power-constrained industrial, automotive, and medical systems.

FAQ

What is the maximum sampling rate supported by the AD7904BRU?

The AD7904BRU supports a maximum throughput rate of 1 MSPS, achieved with a 20 MHz SCLK and 16 SCLK cycles per conversion. This rate is maintained across the full AVDD range (2.7 V to 5.25 V) and ambient temperature range (−40°C to +85°C for B version). At lower SCLK frequencies, the throughput scales linearly - e.g., 10 MHz SCLK yields 500 kSPS. The AD7904BRU does not use oversampling or interpolation, so the 1 MSPS rate reflects true Nyquist-limited acquisition capability.

Does the AD7904BRU require an external reference voltage?

Yes, the AD7904BRU requires an external reference voltage applied to the REFIN pin. The datasheet specifies 2.5 V ±1% for guaranteed performance, and REFIN directly sets the full-scale input range (0 V to REFIN or 0 V to 2 × REFIN depending on the RANGE bit setting). No internal reference is provided; using a precision external reference such as the ADR4525 or REF192 is necessary to achieve the published INL, gain error, and SNR specifications. The REFIN input impedance is 36 kΩ typical at 1 MSPS, requiring low-output-impedance buffering for optimal performance.

How does the channel sequencer function in the AD7904BRU?

The AD7904BRU's sequencer cycles through VIN0–VIN3 based on the SEQ1/SEQ0 bits in the control register. When configured for automatic sequencing (SEQ1 = 1, SEQ0 = 0), it converts channels in order VIN0 → VIN1 → VIN2 → VIN3 and repeats. Each conversion is triggered by CS, and the channel address appears in bits D13–D12 of the DOUT stream. The sequencer eliminates the need for repeated control register writes, reducing host processor overhead. Sequencing behavior is independent of the ADD1/ADD0 bits, which only affect manual channel selection mode.

What are the logic voltage requirements for interfacing with the AD7904BRU?

The AD7904BRU uses separate supplies for analog (AVDD) and digital I/O (VDRIVE), both rated 2.7 V to 5.25 V. Logic thresholds are defined relative to VDRIVE: VINH ≥ 0.7 × VDRIVE and VINL ≤ 0.3 × VDRIVE. This allows direct connection to 3 V or 5 V microcontrollers without level shifters. For example, with VDRIVE = 3.3 V, CS and SCLK must swing between 0 V and 3.3 V, and DOUT outputs VOH ≥ 3.1 V and VOL ≤ 0.4 V. The VDRIVE pin must be decoupled with a 100 nF ceramic capacitor close to the package.

Is the AD7904BRU pin-compatible with other members of the AD7904/AD7914/AD7924 family?

Yes, the AD7904BRU is pin-compatible and footprint-compatible with AD7914BRU and AD7924BRU in the same 16-lead TSSOP package. All share identical pin configuration, power domains (AVDD, VDRIVE, AGND), reference interface (REFIN), and serial protocol (CS/SCLK/DIN/DOUT). Firmware and PCB layout can be reused across the family - only the control register configuration and expected data length (8/10/12 bits) differ. This enables scalable design reuse: start with AD7904BRU for cost-sensitive prototypes, then migrate to AD7914BRU or AD7924BRU for higher-resolution variants without hardware changes.