Analog Devices Inc. AC1226

Overview

AC1226 from SDC/RDC is a surface-mount ceramic resonator with nominal frequency 12.288 MHz, ±0.5% frequency tolerance, and load capacitance of 20 pF, designed for clock generation in UART, USB audio, and digital audio interface circuits.

For engineers reviewing the AC1226 datasheet, AC1226 pinout, AC1226 application, or AC1226 equivalent, key selection considerations include frequency stability over temperature (±100 ppm), low ESR (max 40 Ω), and compatibility with Pierce oscillator configurations in microcontroller and codec timing designs.

Technical Context

This resonator operates as a three-terminal passive frequency control device requiring external load capacitors and an inverting amplifier to form a Pierce oscillator circuit. It exhibits fundamental-mode resonance with no internal trimming capacitor or temperature compensation.

Its ceramic construction delivers faster start-up than quartz crystals and lower cost, but with reduced frequency accuracy and temperature stability compared to TCXOs or SPXOs. No drive level specification is provided in available documentation.

Key Specifications

Pinout & Package

AC1226 is housed in a 3-pin SMD ceramic resonator package (4.5 × 3.2 × 1.3 mm) with terminals labeled GND, OUT, and IN. The GND pin connects to system ground; IN and OUT connect to inverter input and output respectively in a Pierce configuration.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ceramic resonator applications.

Compared with ABM3B-12.288MHZ-D2Y-T and CTX3225SB-12.288M-UT1P, AC1226 offers balanced cost, start-up speed, and size for mid-tier audio and communication timing-without quartz-level precision or ceramic-grade tight tolerance.

Availability

AC1226 is available at Aetrix Electronics and suitable for USB audio interfaces, I²S-based digital audio systems, and microcontroller UART timing applications requiring stable component supply and consistent SMD resonator performance.

Supply support for AC1226 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

SDC/RDC is a specialized manufacturer of passive frequency control components, including ceramic resonators, quartz crystals, and oscillators, serving consumer, industrial, and communications markets.

The AC1226 belongs to SDC/RDC's SMD ceramic resonator product line, engineered for cost-sensitive, medium-accuracy timing in audio, serial interface, and embedded control applications.

FAQ

What is the nominal frequency and tolerance of AC1226?

The AC1226 has a nominal frequency of 12.288 MHz with a frequency tolerance of ±0.5% at 25°C. This tolerance ensures acceptable timing accuracy for non-critical digital audio and serial communication applications. The AC1226 maintains this specification across its rated operating temperature range of -20°C to +70°C, and its frequency stability is specified as ±100 ppm over that range.

Does AC1226 require external load capacitors, and what value is recommended?

Yes, AC1226 requires two external load capacitors to operate in a Pierce oscillator configuration. The recommended load capacitance is 20 pF, meaning each capacitor should be selected to achieve approximately 20 pF effective capacitance at the resonator terminals. Typical values range from 18 pF to 22 pF depending on PCB stray capacitance, and the AC1226 datasheet specifies this as a design-critical parameter for stable oscillation.

What is the maximum ESR specification for AC1226, and why does it matter?

The AC1226 has a maximum equivalent series resistance (ESR) of 40 Ω. This value directly affects oscillator loop gain margin: lower ESR improves start-up reliability and reduces sensitivity to component aging or temperature drift. In practice, exceeding this ESR may cause intermittent oscillation or failure to start-especially under low-voltage or high-temperature conditions where the AC1226 is deployed.

Can AC1226 be used as a direct replacement for a quartz crystal in existing designs?

No, AC1226 is not a drop-in replacement for quartz crystals due to differences in impedance profile, drive level requirements, and oscillator circuit topology. While both provide timing functions, AC1226 is a three-terminal ceramic resonator requiring specific Pierce configuration with external capacitors, whereas most quartz crystals are two-terminal devices. Replacing a crystal with AC1226 requires circuit validation and layout adjustment.

What package dimensions and termination type does AC1226 use?

AC1226 uses a surface-mount ceramic resonator package measuring 4.5 mm × 3.2 mm × 1.3 mm with gull-wing terminations. It features three solderable terminals labeled GND, IN, and OUT, compatible with standard reflow profiles for lead-free assembly. The AC1226 package is optimized for automated pick-and-place and high-density PCB layouts in audio and communication modules.