Texas Instruments SN74ACT7806-25DL

Overview

SN74ACT7806-25DL from Texas Instruments is a 256-word × 18-bit strobed FIFO memory IC designed for high-speed data buffering between asynchronous clock domains. It delivers 15 ns access time, supports up to 40 MHz clock frequency (per -25 speed grade), features programmable almost-full/almost-empty flags, and operates over 0°C to 70°C. It is used in telecom line cards for jitter-tolerant data alignment.

For engineers reviewing the SN74ACT7806-25DL datasheet, SN74ACT7806-25DL pinout, SN74ACT7806-25DL application, or SN74ACT7806-25DL equivalent, key selection criteria include its 56-pin SSOP package, dual asynchronous load/unload clocks, full/empty/half-full status flags, and compatibility with Widebus™-based system interconnects.

Technical Context

The SN74ACT7806-25DL implements a synchronous SRAM-based FIFO core with independent write (LDCK) and read (UNCK) pointers, enabling true first-in-first-out operation across mismatched clock domains. Its internal stack pointer logic tracks occupancy in real time and drives FULL, EMPTY, HF, and programmable AF/AE flags.

Flag behavior is deterministic: FULL goes low at exactly 256 words written, EMPTY goes low when zero words remain, and HF asserts high at ≥128 words. The AF/AE flag supports user-defined thresholds (X/Y) via D0–D6 latching on reset-initiated LDCK edges, with default X=Y=32.

Key Specifications

Pinout & Package

Packaged in a 56-pin Shrink Small-Outline Package (SSOP-DL), 300-mil body width, 25-mil center-to-center lead pitch, RoHS-compliant NIPDAU finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar FIFO memory applications.

Compared with SN74ACT7806-25DL, the -20DL variant offers tighter timing for demanding interfaces but increases supply current, while the -40DL trades speed for lower power and thermal footprint-both retain identical functionality, flag behavior, and PCB layout.

Availability

SN74ACT7806-25DL is available at Aetrix Electronics and suitable for telecom infrastructure, digital video equipment, industrial PLCs, and automated test systems requiring stable component supply across long production lifecycles.

Supply support for SN74ACT7806-25DL 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions, with decades of heritage in high-reliability interface and memory products.

The SN74ACT7806-25DL belongs to TI's Widebus™ family of advanced CMOS FIFOs, engineered specifically for high-speed, low-latency data buffering in multi-clock-domain systems such as communications backplanes and real-time instrumentation.

FAQ

What is the maximum operating frequency of the SN74ACT7806-25DL?

The SN74ACT7806-25DL supports a maximum clock frequency of 40 MHz for both LDCK and UNCK inputs, as specified in the timing requirements table for the -25 speed grade. This rating assumes VCC = 4.5 V to 5.5 V and operation within 0°C to 70°C. Exceeding this frequency may result in setup/hold violations or incorrect flag assertion.

How does the AF/AE flag programming work on the SN74ACT7806-25DL?

After asserting RESET, the SN74ACT7806-25DL enters programming mode when PEN is held low before the first LDCK↑. On that rising edge, D0–D6 latch as the almost-empty offset (X). A second LDCK↑ with PEN still low latches D0–D6 as the almost-full offset (Y). Default values (X=Y=32) apply if PEN remains high.

Is the SN74ACT7806-25DL pin-compatible with other members of the ACT78xx FIFO family?

Yes, the SN74ACT7806-25DL is pin-to-pin compatible with SN74ACT7804 (128×18) and SN74ACT7814 (512×18), sharing identical 56-pin DL package, pin functions, and control logic. This allows board-level scalability-swap parts to adjust buffer depth without layout changes.

What happens to the Q outputs during RESET on the SN74ACT7806-25DL?

During RESET assertion, the SN74ACT7806-25DL resets internal pointers and forces FULL high, EMPTY low, and HF low-but the Q outputs retain their last driven logic states and are not forced to any defined level. Output-enable (OE) must be used to place Q0–Q17 in high-Z if bus isolation is required during reset.

Does the SN74ACT7806-25DL support simultaneous read and write operations?

Yes, the SN74ACT7806-25DL supports concurrent LDCK and UNCK activity: data can be loaded on one rising edge while another word is unloaded on a separate rising edge, provided FULL and EMPTY flags permit it. Internal pointer logic ensures atomic updates and avoids race conditions in the 256×18 SRAM array.