Analog Devices Inc. AD7688BRMRL7

Overview

AD7688BRMRL7 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/DSP-compatible serial interface, and targets high-precision data acquisition in battery-powered instrumentation and medical devices.

For engineers reviewing the AD7688BRMRL7 datasheet, AD7688BRMRL7 pinout, AD7688BRMRL7 application, or AD7688BRMRL7 equivalent, key selection criteria include its 96.5 dB dynamic range, −118 dB THD at 20 kHz, 2.5 ns aperture delay, 1 nA standby current, and dual-package support (10-lead MSOP/LFCSP) for space-constrained embedded systems.

Technical Context

The AD7688BRMRL7 uses a charge redistribution DAC architecture with two identical 16-bit binary-weighted capacitor arrays, enabling precise differential sampling without missing codes. Its on-chip track-and-hold acquires voltage difference between IN+ and IN− on the CNV rising edge, with no latency or pipeline delay.

Conversion timing is fully internal: the part requires no external clock for conversion, only SCK for serial readout. The proprietary serial interface supports CS-mode (3-/4-wire) and chain-mode daisy-chaining with BUSY indicator, all compatible with 1.8 V–5 V logic levels via dedicated VIO supply.

Key Specifications

Pinout & Package

AD7688BRMRL7 is available in two pin-compatible 10-lead packages: 3 mm × 3 mm LFCSP (exposed paddle, must be connected to GND) and narrow-body MSOP. Both packages share identical pin numbering and function mapping.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7688BRMRL7, AD7687BRMZ offers identical accuracy in a lower-speed, lower-power variant, while AD7685BRMZ further reduces throughput and power for static-sensing use cases-both retain pin-for-pin compatibility and shared design infrastructure.

Availability

AD7688BRMRL7 is available at Aetrix Electronics and suitable for battery-powered instrumentation, portable medical devices, and industrial process controls requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for AD7688BRMRL7 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 AD7688BRMRL7 belongs to Analog Devices' PulSAR™ family of precision SAR ADCs, engineered for high-speed, low-power, and high-linearity data acquisition in space- and energy-constrained embedded systems.

FAQ

What is the maximum sample rate supported by the AD7688BRMRL7?

The AD7688BRMRL7 supports a maximum throughput of 500 kSPS under specified conditions (VDD = 4.5 V–5.5 V, TA = −40°C to +85°C). This corresponds to a minimum conversion cycle time of 2 µs and enables accurate digitization of signals with up to ~200 kHz bandwidth. At this rate, power dissipation is 21.5 mW at 5 V. The AD7688BRMRL7 maintains full 16-bit performance-including ±1.5 LSB INL and 95.5 dB SNR-across its entire speed range.

Does the AD7688BRMRL7 require an external reference voltage?

Yes, the AD7688BRMRL7 requires an external reference voltage applied to the REF pin. The REF input accepts 0.5 V to VDD (up to 5.5 V), and performance metrics like SNR and THD are specified with VREF = VDD = 5 V. A 10 µF ceramic capacitor (X5R) must be placed directly at the REF pin for stability. While the device does not integrate a reference, its flexible REF range allows use with precision external references (e.g., ADR4550) or ratiometric configurations where VREF tracks VDD.

Can the AD7688BRMRL7 interface directly with a 1.8 V microcontroller?

Yes, the AD7688BRMRL7 supports direct 1.8 V logic interfacing via its dedicated VIO supply pin. When VIO = 1.8 V, digital inputs (CNV, SDI, SCK) recognize VIH ≥ 1.26 V and VIL ≤ 0.54 V, and digital outputs (SDO) drive VOH ≥ 1.5 V and VOL ≤ 0.4 V. This eliminates level-shifters in mixed-voltage systems. The AD7688BRMRL7 maintains full timing compliance (e.g., 20 ns min SCK period) and functional integrity at 1.8 V logic levels.

What is the significance of "no pipeline delay" in the AD7688BRMRL7?

"No pipeline delay" means the AD7688BRMRL7 is a true successive approximation register (SAR) ADC-not a pipelined or sigma-delta type-so conversion results are available immediately after completion, with zero cycles of latency. For the AD7688BRMRL7, the conversion time is 1.6 µs max, and the result appears on SDO within 17 ns after the final SCK falling edge. This deterministic, low-latency behavior is essential for real-time control, multiplexed channel sequencing, and time-critical trigger applications where delayed or buffered outputs would compromise system response.

Is the AD7688BRMRL7 pin-compatible with other PulSAR ADCs?

Yes, the AD7688BRMRL7 is pin-for-pin compatible with AD7685BRMZ, AD7686BRMZ, and AD7687BRMZ in both 10-lead MSOP and 10-lead LFCSP packages. This allows drop-in replacement across the family for design reuse and scalability: AD7685 (100 kSPS), AD7686 (250 kSPS), AD7687 (250 kSPS, pseudo-differential), and AD7688BRMRL7 (500 kSPS, true differential). Shared pinout simplifies layout, firmware adaptation, and qualification testing across product variants.