Analog Devices Inc. AD7694BRMZ

Overview

AD7694BRMZ from Analog Devices is a 16-bit, pseudo-differential, successive approximation register (SAR) analog-to-digital converter with no missing codes (B grade), 250 kSPS throughput at 5 V, ±4 LSB INL, 92 dB S/(N + D) at 20 kHz, and single-supply operation from 2.7 V to 5.25 V. It serves as a precision data acquisition front-end in portable instrumentation requiring low power and high DC/AC accuracy.

For engineers reviewing the AD7694BRMZ datasheet, AD7694BRMZ pinout, AD7694BRMZ application, or AD7694BRMZ equivalent, key selection considerations include its 8-lead MSOP package, SPI-compatible serial interface, 1 nA standby current, pseudo-differential input architecture (0 V to VREF), and absence of pipeline delay - all critical for battery-powered, multiplexed, or space-constrained embedded systems.

Technical Context

The AD7694BRMZ employs a charge redistribution SAR architecture with on-chip track-and-hold, enabling true single-cycle conversion without latency or pipeline delay. Its conversion is initiated by a rising edge on CNV, and results are output synchronously via SDO using a proprietary SPI-compatible 3-wire interface (CNV, SCK, SDO).

It features dynamic reference input impedance requiring local 10 µF ceramic decoupling at REF, supports external VREF up to VDD (1 V to 5.25 V), and scales power linearly with throughput - drawing only 540 µA at 2.7 V/100 kSPS and dropping to 1 nA in standby. Operating temperature range is −40°C to +85°C.

Key Specifications

Pinout & Package

AD7694BRMZ is housed in an 8-lead MSOP package (3.0 mm × 3.0 mm, 0.65 mm pitch), JEDEC MO-187-AA compliant, with exposed pad not connected internally. Pin 1 (REF) is top-left when notch is oriented up; pin numbering proceeds counterclockwise.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit SAR ADC applications.

Compared with LTC1864L and AD7685BRMZ, the AD7694BRMZ uniquely balances 250 kSPS speed, pseudo-differential simplicity, and ultra-low standby current in an 8-pin MSOP - making it optimal for space- and power-constrained unipolar sensing where true differential input is unnecessary.

Availability

AD7694BRMZ is available at Aetrix Electronics and suitable for portable instrumentation, industrial data loggers, and handheld test equipment requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for AD7694BRMZ 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, with R&D and manufacturing operations worldwide.

The AD7694BRMZ belongs to Analog Devices' PulSAR® family of precision SAR ADCs, designed specifically for low-power, high-accuracy data acquisition in battery-operated and space-constrained industrial, medical, and instrumentation systems.

FAQ

What is the maximum recommended reference voltage for AD7694BRMZ?

The AD7694BRMZ supports an external reference voltage (REF) from 1 V up to VDD, with VDD rated from 2.7 V to 5.25 V. Therefore, the maximum REF is 5.25 V when VDD = 5.25 V. Operation at VREF = VDD is explicitly validated in the datasheet and delivers optimal SNR (92 dB) and S/(N + D). Exceeding VDD on REF violates Absolute Maximum Ratings and may damage the device.

Does AD7694BRMZ require an external clock for conversion?

No, the AD7694BRMZ does not require an external clock for conversion. It contains an on-chip conversion clock, so the serial clock (SCK) is used only for data readout after conversion completes. Conversion is triggered solely by the CNV rising edge, and the internal timing ensures deterministic tCONV (3.2 µs at 5 V). This eliminates clock distribution complexity and jitter sensitivity in the signal chain.

Can AD7694BRMZ interface directly with a 3.3 V microcontroller SPI port?

Yes, AD7694BRMZ supports 3.3 V digital interface operation. Its VIH minimum is 1.9 V at VDD = 3.3 V, and VIL maximum is 0.45 V at VDD = 2.7 V - both compatible with standard 3.3 V CMOS logic levels. The SDO output VOH is VDD − 0.3 V, ensuring valid high-level signaling into 3.3 V inputs. No level-shifting is required when VDD = 3.3 V.

What is the purpose of the IN− pin on AD7694BRMZ?

The IN− pin on AD7694BRMZ serves as the pseudo-differential ground sense reference - not a true differential input. It defines the common-mode baseline for the IN+ input, allowing rejection of noise common to both nodes. IN− should be connected to the analog ground plane or to the remote ground of the signal source (e.g., sensor ground), enabling accurate measurement of small signals over noisy or long traces without requiring a fully differential driver.

How does AD7694BRMZ achieve 1 nA standby current?

The AD7694BRMZ achieves 1 nA standby current by powering down all internal circuitry - including the reference buffer, track-and-hold, and digital logic - between conversions. This occurs automatically when CNV is held high and no conversion is active. The specification is measured at 25°C with all digital inputs forced to VDD or GND; actual current remains sub-50 nA over the full −40°C to +85°C range, enabling decade-scale battery life in duty-cycled systems.