Analog Devices Inc. AD7942BCPZRL7

Overview

AD7942BCPZRL7 from Analog Devices is a 14-bit, pseudo-differential successive approximation register (SAR) ADC with 250 kSPS throughput, ±1 LSB INL max, 85 dB SINAD at 20 kHz, and no pipeline delay. It operates from a single 2.3 V to 5.5 V supply, supports 1.8 V–5 V logic via separate VIO, and targets precision data acquisition in space-constrained, low-power systems.

For engineers reviewing the AD7942BCPZRL7 datasheet, AD7942BCPZRL7 pinout, AD7942BCPZRL7 application, or AD7942BCPZRL7 equivalent, key selection factors include its pseudo-differential input architecture, daisy-chain SPI interface, sub-μW standby power (1 nA), 10-lead LFCSP package, and pin compatibility with AD7685 for design reuse.

Technical Context

The AD7942BCPZRL7 uses a charge redistribution SAR architecture with integrated track-and-hold, enabling true single-cycle conversion without latency. Its analog front end accepts 0 V to VREF differential inputs referenced to IN−, with CMRR of 65 dB at 250 kHz and −3 dB bandwidth of 2 MHz.

Digital operation relies on a proprietary SPI-compatible serial interface supporting both CS mode (with busy indicator) and chain mode (daisy-chaining multiple ADCs). Conversion timing is internally clocked-SCK only shifts out results-and VIO decouples logic voltage (1.8 V/2.5 V/3 V/5 V) from analog supply (VDD), isolating noise-sensitive analog performance.

Key Specifications

Pinout & Package

The AD7942BCPZRL7 is housed in a 3 mm × 3 mm, 10-lead LFCSP (Lead Frame Chip Scale Package) with exposed paddle connected to GND. This thermally enhanced, surface-mount package supports high-density PCB layouts and offers θ_JA = 48.7°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 14-bit SAR ADC applications.

Compared with AD7685BRMZ and ADS8860IDRCT, the AD7942BCPZRL7 uniquely balances 14-bit precision, 250 kSPS speed, 1 nA standby current, pseudo-differential input architecture, and hardware daisy-chain capability - making it the most suitable choice for compact, battery-aware, multi-sensor data acquisition systems requiring deterministic timing and low EMI susceptibility.

Availability

AD7942BCPZRL7 is available at Aetrix Electronics and suitable for battery-powered equipment, medical instruments, process controls, and portable instrumentation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for AD7942BCPZRL7 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 AD7942BCPZRL7 belongs to Analog Devices' PulSAR® family of precision SAR ADCs, designed specifically for high-fidelity, low-power, single-supply data acquisition in portable, industrial, and medical systems where accuracy, size, and energy efficiency are critical.

FAQ

What is the maximum recommended reference voltage for AD7942BCPZRL7?

The AD7942BCPZRL7 supports an external reference voltage (REF) from 0.5 V up to VDD. When VDD = 5.5 V, VREF may be as high as 5.5 V; however, the datasheet specifies optimal AC performance (e.g., 85 dB SINAD) at VREF = 5 V. Using VREF = VDD simplifies supply architecture but requires ensuring VDD stability, as reference noise directly impacts LSB accuracy. The AD7942BCPZRL7 does not include an internal reference - all precision depends on external REF quality and decoupling (10 μF ceramic capacitor recommended).

Does AD7942BCPZRL7 support true differential input mode?

No, the AD7942BCPZRL7 implements a pseudo-differential input architecture: IN+ is sampled with respect to IN−, which serves as a dedicated ground-sense node, not an active complementary input. It does not accept true differential signals (e.g., ±2.5 V) nor perform subtraction internally. IN− must be connected to a quiet analog ground or remote sensor ground to reject common-mode noise - confirmed by its 65 dB CMRR at 250 kHz. For true differential input capability, consider the AD768x or AD798x families instead of the AD7942BCPZRL7.

Can AD7942BCPZRL7 operate with a 1.8 V digital interface while using a 5 V analog supply?

Yes. The AD7942BCPZRL7 features a separate VIO pin that accepts 1.8 V to VDD + 0.3 V, allowing independent scaling of digital I/O voltage. With VDD = 5 V and VIO = 1.8 V, the device maintains full analog performance (250 kSPS, 85 dB SINAD) while interfacing directly to 1.8 V FPGAs or low-voltage microcontrollers - no level-shifting circuitry required. Digital timing parameters (e.g., t_SCK, t_DSDO) are specified down to VIO = 2.3 V; operation at 1.8 V is supported per the "VIO Range" specification (1.8 V to VDD + 0.3 V) and confirmed in application notes for the AD7942BCPZRL7.

What is the aperture delay of AD7942BCPZRL7 and why does it matter?

The AD7942BCPZRL7 has a typical aperture delay of 2.5 ns at VDD = 5 V - the time between the CNV rising edge and when the internal track-and-hold circuit freezes the analog input. This ultra-low, tightly specified delay minimizes sampling uncertainty in high-frequency applications, directly improving effective resolution when undersampling or capturing fast transients. Combined with 1.8 μs transient response, it ensures accurate capture of full-scale step events, making the AD7942BCPZRL7 suitable for time-domain analysis in oscilloscope-like front ends and motor control current sensing where timing jitter must be <10 ps RMS.

Is AD7942BCPZRL7 pin-compatible with any other Analog Devices ADCs?

Yes, the AD7942BCPZRL7 is explicitly pin-for-pin compatible with the 16-bit AD7685, sharing identical 10-lead MSOP and LFCSP footprints and identical pin functions (REF, VDD, IN+, IN−, GND, CNV, SDO, SCK, SDI, VIO). This allows direct PCB-level replacement to trade resolution for speed/power or vice versa without layout changes. Compatibility is documented in Table 1 and the General Description section of the AD7942BCPZRL7 datasheet - no adapter or firmware modification is needed beyond adjusting software gain and offset calibration constants.