Analog Devices Inc. AD9238BST-20

Overview

AD9238BST-20 from Analog Devices is a dual-channel, 12-bit, 20 MSPS analog-to-digital converter (ADC) fabricated in advanced CMOS, operating from a single 3 V supply (2.7 V to 3.6 V). It features differential input with 500 MHz bandwidth, 70 dB SNR at 2.4 MHz input, and 85 dB crosstalk immunity. It is used in ultrasound equipment and handheld scopemeters where low power (180 mW total) and high channel isolation are critical.

For engineers reviewing the AD9238BST-20 datasheet, AD9238BST-20 pinout, AD9238BST-20 application, or AD9238BST-20 equivalent, key selection considerations include its 20 MSPS sampling rate, LQFP-64 package, dual independent clock inputs (CLK_A/CLK_B), flexible 1 V_p-p to 2 V_p-p analog input range, and support for offset binary or twos complement output format.

Technical Context

The AD9238BST-20 employs a multistage differential pipelined architecture with output error correction logic to guarantee 12-bit accuracy and no missing codes across −40°C to +85°C. Its dual sample-and-hold amplifiers (SHAs) enable simultaneous sampling of two independent analog channels with exceptional inter-channel isolation (>85 dB).

It integrates an internal voltage reference (1.0 V or 0.5 V mode), clock duty cycle stabilizer (DCS), and multiplexed data output option. Digital outputs are LVCMOS-compatible, driven by DRVDD (2.25 V to 3.6 V), with pipeline latency fixed at 7 clock cycles and aperture uncertainty of 0.5 ps rms.

Key Specifications

Pinout & Package

The AD9238BST-20 is housed in a Pb-free, 64-lead LQFP (Low-Profile Quad Flat Package) with exposed pad requiring connection to AGND. Pin pitch is 0.5 mm; body size is 10 mm × 10 mm × 1.4 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD9238BST-40 and AD9248BST-20, the AD9238BST-20 delivers the lowest power (180 mW) and highest SNR (70.4 dB) at 20 MSPS among pin-compatible dual 12-bit ADCs, making it ideal for portable, battery-constrained systems requiring wide analog bandwidth and strong channel isolation.

Availability

AD9238BST-20 is available at Aetrix Electronics and suitable for ultrasound beamforming, IF sampling receivers, and battery-powered scopemeters requiring stable component supply and long-term industrial temperature support (−40°C to +85°C).

Supply support for AD9238BST-20 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 AD9238 product line targets high-speed data acquisition in medical imaging, communications, and portable test equipment, emphasizing low power, dual-channel synchronization, and robust RF performance.

FAQ

What is the maximum analog input frequency supported by the AD9238BST-20?

The AD9238BST-20 has a 500 MHz (3 dB) analog input bandwidth, enabling direct sampling of signals up to 10 MHz (Nyquist limit at 20 MSPS). Performance metrics such as SNR and SFDR are characterized up to 100 MHz input, but usable signal fidelity depends on anti-aliasing filtering and layout integrity. The device is commonly deployed for IF sampling in CDMA2000 and WiMAX systems below 20 MHz.

Does the AD9238BST-20 require external reference components?

No, the AD9238BST-20 integrates a precision 1.0 V (or 0.5 V) internal voltage reference with ±35 mV output voltage error and 0.8 mV load regulation. External reference is optional and only needed when higher accuracy or custom scaling is required; the SENSE pin configures internal reference mode, and REFT/REFB pins accept external differential references if used.

How does the clock duty cycle stabilizer (DCS) function in the AD9238BST-20?

The DCS circuit in the AD9238BST-20 actively corrects input clock duty cycle deviations, maintaining SNR and SFDR performance across 30%–70% duty cycle range. When enabled (DCS pin tied high), it eliminates sensitivity to clock generator asymmetry-critical for systems using simple crystal oscillators or PLLs without dedicated duty cycle correction. Measured SINAD remains stable within ±0.2 dB over this range.

Can the AD9238BST-20 operate with independent clock sources on CLK_A and CLK_B?

Yes, the AD9238BST-20 supports fully independent clock inputs on CLK_A and CLK_B, allowing asynchronous sampling of two unrelated analog signals. Each channel's SHA and ADC core operate autonomously; however, simultaneous conversion timing is not guaranteed unless clocks are phase-locked. For coherent I/Q sampling, synchronous clocking with matched trace lengths is recommended.

What is the purpose of the MUX_SELECT pin on the AD9238BST-20?

The MUX_SELECT pin configures the AD9238BST-20's output multiplexing mode: when high, it disables multiplexing and presents full 12-bit parallel outputs on both Channel A and Channel B buses; when low, it enables time-multiplexed output where D0_A–D11_A and D0_B–D11_B share the same physical bus in alternating cycles, reducing PCB routing complexity in resource-constrained designs.