Analog Devices Inc. AD7688BRMZ

Overview

AD7688BRMZ from Analog Devices is a 16-bit, charge redistribution successive approximation ADC with true differential input, ±1.5 LSB max INL, 500 kSPS throughput, and no pipeline delay. It operates from a single 5 V supply with 1.8 V–5 V logic interface (VIO), supports daisy-chain SPI/QSPI/MICROWIRE-compatible serial interface, and targets high-precision data acquisition in space-constrained industrial and medical instrumentation.

For engineers reviewing the AD7688BRMZ datasheet, AD7688BRMZ pinout, AD7688BRMZ application, or AD7688BRMZ equivalent, this page delivers verified technical context, real-world design meaning for key specs, validated pin functions, confirmed alternatives, and supply support for battery-powered equipment, process control systems, and portable medical instruments requiring low-power, high-linearity analog-to-digital conversion.

Technical Context

The AD7688BRMZ implements a charge redistribution DAC architecture with dual 16-bit capacitor arrays, enabling precise differential sampling without latency. Its on-chip track-and-hold acquires the voltage difference between IN+ and IN− on the CNV rising edge, with 2.5 ns aperture delay and 9 MHz −3 dB input bandwidth.

Conversion is clocked internally-no external SCK required for core operation-while the SPI-compatible serial interface supports CS mode (3- or 4-wire) and chain mode with BUSY indicator. Power scales linearly: 3.75 µW at 100 SPS, 21.5 mW at 500 kSPS, and standby current is 1 nA.

Key Specifications

Pinout & Package

AD7688BRMZ is available in two 10-lead packages: 3 mm × 3 mm LFCSP (exposed paddle, must be connected to GND) and narrow-body MSOP. Both are RoHS-compliant and rated for −40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7688BRMZ, AD7687BRMZ trades half the throughput for lower power and relaxed timing, while ADS8860IDRCT offers higher speed at the cost of input flexibility and added signal conditioning overhead.

Availability

AD7688BRMZ is available at Aetrix Electronics and suitable for battery-powered equipment, industrial process controls, and portable medical instruments requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for AD7688BRMZ 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 Wilmington, MA, with R&D and manufacturing across North America, Europe, and Asia.

The AD7688BRMZ belongs to the PulSAR™ family of precision SAR ADCs designed for applications demanding high resolution, low power, and zero-latency conversion-especially where space, thermal, and energy constraints preclude sigma-delta or pipeline architectures.

FAQ

What is the maximum recommended reference voltage for AD7688BRMZ?

The AD7688BRMZ supports an external reference voltage (REF) from 0.5 V up to VDD, with VDD specified from 4.5 V to 5.5 V. Therefore, the maximum REF is 5.5 V. However, typical operation uses REF = VDD = 5 V to achieve full ±5 V differential input range and optimal SNR (95.5 dB). Using REF > VDD risks violating absolute maximum ratings and is not supported. The AD7688BRMZ reference input must be decoupled with a 10 µF ceramic capacitor placed close to the REF pin.

Does AD7688BRMZ require an external clock for conversion?

No, the AD7688BRMZ does not require an external clock for the core conversion process. It contains an internal conversion clock, so the rising edge of CNV alone initiates sampling and conversion. The SCK signal is used solely for serial data readout-not for timing the ADC core-and can be paused or stopped without affecting conversion integrity. This eliminates clock distribution challenges and reduces EMI in sensitive analog sections. The AD7688BRMZ remains fully functional even with SCK inactive during acquisition.

Can AD7688BRMZ interface directly with a 1.8 V microcontroller?

Yes, the AD7688BRMZ supports 1.8 V logic levels via its dedicated VIO supply pin. When VIO = 1.8 V, the digital inputs (CNV, SDI, SCK) accept VIH ≥ 1.26 V and VIL ≤ 0.54 V, and the SDO output drives VOH ≥ 1.5 V and VOL ≤ 0.4 V-fully compatible with standard 1.8 V CMOS interfaces. No level-shifting circuitry is needed. This allows seamless integration with ultra-low-power MCUs like the STM32L4 or EFM32 Gecko, preserving the AD7688BRMZ's 1 nA standby current advantage in sleep modes.

What is the significance of "no missing codes" in AD7688BRMZ specifications?

"No missing codes" means that the AD7688BRMZ guarantees monotonic transfer behavior across its entire 16-bit output range (0x0000 to 0xFFFF): every possible 16-bit code appears at least once as the input sweeps from negative to positive full scale. This is essential for closed-loop control, position feedback, and safety-critical measurements where code gaps could cause step-function errors or instability. The AD7688BRMZ achieves this with ±1.5 LSB INL and ±1 LSB DNL (typ), ensuring robustness even under temperature variation and supply ripple-critical for reliable operation in the AD7688BRMZ's target applications.

How does the daisy-chain mode work on AD7688BRMZ?

In daisy-chain mode, multiple AD7688BRMZ devices share one SDO line and one SCK line. SDI is driven low during the CNV rising edge to activate chain mode. Each AD7688BRMZ shifts its 16-bit result onto SDO with a 16-cycle delay relative to the previous device. The host reads all results sequentially on a single SDO line-e.g., 3 devices yield 48 bits in 48 SCK cycles. CNV must be asserted synchronously across all devices. This eliminates individual chip-select lines and simplifies routing in multi-channel systems, making it ideal for compact data acquisition modules using the AD7688BRMZ.