Analog Devices Inc. AD7643BSTZ

Overview

AD7643BSTZ from Analog Devices is an 18-bit, 1.25 MSPS charge redistribution SAR analog-to-digital converter with fully differential input, internal 2.048 V reference (±8 ppm/°C drift), no pipeline delay, and dual serial/parallel interface support. It operates from a single 2.5 V supply and delivers 93.5 dB SINAD at 20 kHz for high-fidelity data acquisition in medical instrumentation and spectrum analysis.

For engineers reviewing the AD7643BSTZ datasheet, AD7643BSTZ pinout, AD7643BSTZ application, or AD7643BSTZ equivalent, key selection considerations include its true differential ±VREF input range, hardware-calibrated INL (±3 LSB max), 50 MHz −3 dB input bandwidth, power-down mode (2 μW), and compatibility with SPI/QSPI/MICROWIRE/DSP host controllers.

Technical Context

The AD7643BSTZ implements a capacitor-based charge redistribution SAR architecture with on-chip calibration logic, eliminating latency and enabling asynchronous sampling. Its internal reference buffer supports both internal (2.048 V) and external reference configurations via PDREF/PDBUF control pins.

Dual interface flexibility is achieved through MODE[1:0] configuration: 18-/16-/8-bit parallel bus or 2-wire serial (master/slave), with programmable SCLK division (DIVSCLK[1:0]), SYNC polarity (INVSYNC), and data format (straight binary/twos complement via OB/2C).

Key Specifications

Pinout & Package

AD7643BSTZ is packaged in a Pb-free 48-lead LFCSP (7 mm × 7 mm, 0.5 mm pitch) with exposed pad for thermal enhancement. Pin functions are validated per Analog Devices Rev. A datasheet Figures 4 and 5 and Table 6.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-resolution SAR ADC applications.

Compared with AD7643BSTZ, AD7641BCPZ offers identical electrical performance in a thermally superior LFCSP package, while AD7622BCPZ trades 2 bits of resolution for double the throughput and removes integrated reference burden - enabling optimization for either precision or speed within the same system architecture.

Availability

AD7643BSTZ is available at Aetrix Electronics and suitable for medical instrumentation, high-speed data acquisition, and spectrum analysis requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for AD7643BSTZ 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 AD7643BSTZ belongs to the PulSAR® family of precision SAR ADCs, designed specifically for applications demanding high resolution, fast throughput, and integrated reference stability in demanding industrial and instrumentation environments.

FAQ

What is the maximum input voltage range supported by the AD7643BSTZ?

The AD7643BSTZ supports a fully differential input range of ±VREF, where VREF can be up to 2.5 V. With the internal 2.048 V reference enabled, this yields a ±2.048 V input range. When using an external reference, the input range scales linearly - for example, a 2.5 V external reference gives ±2.5 V range. Input pins IN+ and IN− must remain within −0.1 V to AVDD relative to AGND.

Does the AD7643BSTZ require external calibration for production use?

No, the AD7643BSTZ is hardware factory calibrated and tested for both AC parameters (e.g., SNR, THD, SINAD) and DC parameters (gain, offset, INL) across temperature. This eliminates the need for system-level calibration in most applications, though users may perform optional end-system verification using known reference signals.

How does the MODE[1:0] pin configuration affect the AD7643BSTZ interface behavior?

The MODE[1:0] pins configure the AD7643BSTZ for four distinct interface modes: 00 = 18-bit parallel, 01 = 16-bit parallel (high/low word selectable via A0), 10 = 8-bit parallel (three byte options via A0/A1), and 11 = serial interface. Each mode reassigns D0–D9 pins accordingly, as defined in Table 7 of the AD7643BSTZ datasheet Rev. A.

Can the AD7643BSTZ operate with an external reference while retaining use of the internal reference buffer?

Yes. The AD7643BSTZ supports hybrid reference operation: set PDREF = high (disable internal reference) and PDBUF = low (enable buffer), then apply 1.2 V to REFBUFIN. The internal buffer amplifies this to 2.048 V on the REF pin - allowing high-precision external reference conditioning without discrete op-amps.

What is the purpose of the TEMP pin on the AD7643BSTZ, and how is it used?

TEMP is an analog output pin providing a voltage proportional to die temperature: 278 mV at 25°C with 1 mV/°C sensitivity. It is internally connected to a bandgap-based sensor and requires no external components. Users read TEMP with a separate ADC or comparator to monitor junction temperature for thermal derating or system diagnostics - the AD7643BSTZ itself does not process this signal digitally.