Analog Devices Inc. AD4681BCPZ-RL

Overview

AD4681BCPZ-RL from Analog Devices is a 16-bit, dual simultaneous sampling, fully differential SAR ADC with 500 kSPS throughput, 92.5 dB SNR (VREF = 3.3 V), ±1.5 LSB INL max, and integrated 2.5 V reference (10 ppm/°C). It operates from −40°C to +125°C in motor control current sensing and power quality monitoring systems requiring precise, synchronized dual-channel acquisition.

For engineers reviewing the AD4681BCPZ-RL datasheet, AD4681BCPZ-RL pinout, AD4681BCPZ-RL application, or AD4681BCPZ-RL equivalent, key selection considerations include dual-channel timing match (26 ps aperture delay match), oversampling support (up to 8× OSR for 100 dB dynamic range), alert threshold functionality, and LFCSP-16 package compatibility with high-density industrial PCB layouts.

Technical Context

The AD4681BCPZ-RL implements two independent SAR conversion cores sharing a common serial interface, each with dedicated differential input pairs (AINA±, AINB±) sampled simultaneously on the falling edge of CS. Its internal 2.5 V reference is buffered and accessible via REFIO, while external reference support extends to 3.3 V with 0.26 mA typical draw at 500 kSPS.

Oversampling is implemented via on-chip rolling average blocks, configurable up to 8× OSR to boost effective resolution and suppress noise-enabling 100 dB dynamic range without external DSP. The device supports twos-complement output coding, 1.65 V–3.6 V logic supply (VLOGIC), and low-latency readback modes for real-time control loops.

Key Specifications

Pinout & Package

AD4681BCPZ-RL is housed in a 3 mm × 3 mm, 16-lead LFCSP (CP-16-451) with exposed pad (EPAD) requiring solder connection to PCB ground for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD4680BCPZ-RL, AD4681BCPZ-RL trades 2× throughput for 35% lower power and identical thermal performance; versus AD7381BCPZ-RL, it adds 2-bit resolution, true differential inputs, integrated reference, and alert functionality - justifying its use in closed-loop safety-critical systems.

Availability

AD4681BCPZ-RL is available at Aetrix Electronics and suitable for motor control position feedback, power quality monitoring, and Erbium-doped fiber amplifier (EDFA) applications requiring stable component supply, extended temperature operation, and long-term industrial lifecycle support.

Supply support for AD4681BCPZ-RL 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, serving industrial, automotive, communications, and healthcare markets since 1965.

The AD4680/AD4681 product line was designed specifically for high-accuracy, dual-channel data acquisition in real-time control systems - emphasizing simultaneous sampling integrity, low power at extended temperature, and integrated diagnostics for functional safety compliance.

FAQ

What is the maximum external reference voltage supported by the AD4681BCPZ-RL?

The AD4681BCPZ-RL supports an external reference voltage range of 2.49 V to 3.4 V on the REFIO pin. Operation with a 3.3 V external reference yields optimal SNR (92.5 dB typical) and enables 100 µV LSB size at 16-bit resolution. Reference current draw is 0.23–0.26 mA at 500 kSPS, requiring proper decoupling with a 1 µF capacitor to GND as specified in the AD4681BCPZ-RL datasheet.

Does the AD4681BCPZ-RL require power supply sequencing during startup?

No, the AD4681BCPZ-RL does not require strict power supply sequencing. VCC and VLOGIC may be applied in any order without risk of latch-up or damage. However, an external reference must be applied only after both VCC and VLOGIC are stable. The AD4681BCPZ-RL achieves 1% internal reference settling in 5 ms and supports first conversion 11 ms after power-up - verified across −40°C to +125°C.

How is the ALERT function configured on the AD4681BCPZ-RL?

The ALERT function on the AD4681BCPZ-RL is enabled via the ALERT register and uses the SDOB/ALERT pin as an open-drain output. Thresholds are set independently for each channel using ALERT_LOW_THRESHOLD and ALERT_HIGH_THRESHOLD registers. When either ADC result exceeds programmed limits, the pin asserts low within 200 ns (tALERTS). Configuration requires writing to CONFIGURATION2 register to assign SDOB/ALERT to ALERT mode - all operations executed via the standard SPI interface of the AD4681BCPZ-RL.

Can the AD4681BCPZ-RL perform oversampling without external processor involvement?

Yes, the AD4681BCPZ-RL includes dedicated on-chip oversampling blocks that operate autonomously. When oversampling ratio (OSR) is set via the CONFIGURATION1 register (e.g., OSR = 4× or 8×), the device internally averages successive conversions and outputs a single enhanced-result word via SDOA/SDOB. No host processor computation is needed - the AD4681BCPZ-RL delivers 100 dB dynamic range directly at 500 kSPS ÷ 8 = 62.5 kSPS effective rate with RES = 1 setting.

What is the recommended analog input filter for the AD4681BCPZ-RL?

Analog Devices recommends a differential RC filter on each analog input pair (AINA±, AINB±) with R = 33 Ω and C1 = 68 pF (series shunt) plus C2 = 330 pF (shunt to ground), as validated in the AD4681BCPZ-RL evaluation circuitry. This configuration provides anti-aliasing at ~10 MHz while maintaining settling time compatible with 500 kSPS sampling. Input source impedance must be matched to ≤10 Ω imbalance to avoid differential-to-common-mode conversion errors affecting the AD4681BCPZ-RL's 75 dB CMRR.