Texas Instruments SN74ACT7803-25DL

Overview

SN74ACT7803-25DL from Texas Instruments is a 512 × 18-bit clocked FIFO memory IC designed for asynchronous data buffering between independent clock domains. It supports free-running, asynchronous or coincident read/write clocks up to 40 MHz, delivers 12 ns access time with 50-pF load, and features synchronized input-ready (IR) and output-ready (OR) flags. It is used in bidirectional datapath bridging and width-expansion interfaces in telecom and industrial control systems.

For engineers reviewing the SN74ACT7803-25DL datasheet, SN74ACT7803-25DL pinout, SN74ACT7803-25DL application, or SN74ACT7803-25DL equivalent, key selection considerations include its 56-pin SSOP (DL) package, programmable almost-full/empty thresholds, half-full flag, and compatibility with SN74ACT7805/SN74ACT7813 for drop-in replacement in legacy Widebus™ designs.

Technical Context

The SN74ACT7803-25DL implements a synchronous dual-clock FIFO architecture with independent write and read pointer logic, status-flag synchronization to respective clocks (IR to WRTCLK, OR to RDCLK), and reset-initiated initialization of all flags. Its internal 512 × 18 RAM uses low-power Advanced CMOS technology with patented output edge control (OEC™) to suppress simultaneous switching noise.

It supports programmable AF/AE offsets via D0–D7 latching on PEN-controlled WRTCLK edges, defaulting to X = Y = 64. Bidirectional configuration and 36-bit width expansion are achieved using two devices without external logic, leveraging dedicated enable and flag signals including HF, AF/AE, OE1/OE2, and RDEN/WRTEN1/WRTEN2.

Key Specifications

Pinout & Package

Packaged in a 56-pin Shrink Small-Outline Package (SSOP), DL variant, with 300-mil body width and 25-mil center-to-center lead pitch. Features distributed VCC/GND pins for noise suppression and OEC™ circuitry.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT7805-25DL and SN74ACT7813-25DL, the SN74ACT7803-25DL offers the widest default buffer margin (64-word AF/AE), simplest 18-bit width expansion, and most direct drop-in replacement path in existing Widebus™ designs using the 512×18 configuration.

Availability

SN74ACT7803-25DL is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLC I/O, legacy bus translation, and ATE pattern memory applications requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74ACT7803-25DL 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 delivering analog, embedded processing, and logic solutions with emphasis on reliability, performance, and broad application support.

The SN74ACT7803-25DL belongs to TI's Widebus™ family of high-speed interface ICs, engineered specifically for clock-domain isolation, data buffering, and protocol bridging in industrial, telecom, and instrumentation systems.

FAQ

What is the maximum clock frequency supported by the SN74ACT7803-25DL?

The SN74ACT7803-25DL supports a maximum clock frequency of 40 MHz for both read and write operations, corresponding to a 25-ns clock period. This rating is specified under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C) and verified with CL = 50 pF load. The -25 suffix denotes this speed grade, distinguishing it from -15 (67 MHz), -20 (50 MHz), and -40 (25 MHz) variants. SN74ACT7803-25DL timing compliance assumes proper setup/hold margins and stable power delivery.

How does the AF/AE flag operate on the SN74ACT7803-25DL?

The AF/AE flag on the SN74ACT7803-25DL is a dual-purpose status output that goes high when the FIFO contains ≤X words (almost-empty) or ≥(512−Y) words (almost-full). By default, X = Y = 64. These thresholds can be reprogrammed via D0–D7 latched on WRTCLK edges when PEN is asserted low before the first write. After reset, AF/AE is high. SN74ACT7803-25DL uses this flag for early flow control signaling without requiring external monitoring logic.

Is the SN74ACT7803-25DL pin-compatible with other members of the Widebus™ FIFO family?

Yes, the SN74ACT7803-25DL is pin-to-pin compatible with SN74ACT7805-25DL and SN74ACT7813-25DL in the same DL (56-pin SSOP) package. All share identical pin assignments for clocks, data, enables, flags, and power. Functional differences-such as default AF/AE offset (64 vs. 32) or memory organization (512×18 vs. 1024×9)-do not affect physical layout or PCB footprint. SN74ACT7803-25DL can be substituted without board revision when those functional distinctions align with system requirements.

What is the purpose of the PEN pin on the SN74ACT7803-25DL?

The PEN (Program Enable) pin on the SN74ACT7803-25DL controls latching of D0–D7 as the AF/AE offset values. When PEN is low during a WRTCLK rising edge (and IR is high), the binary value on D0–D7 is stored as the almost-empty offset X; a second low PEN pulse latches Y. PEN must remain high to retain the default X = Y = 64 setting. During programming, write operations are disabled regardless of WRTEN1/WRTEN2 states. SN74ACT7803-25DL requires PEN management only if custom buffer thresholds are needed.

Does the SN74ACT7803-25DL require power-on reset sequencing?

Yes, the SN74ACT7803-25DL must be reset upon power-up. RESET must be asserted low while at least four rising edges occur on both WRTCLK and RDCLK to properly initialize internal pointers and flags (IR, OR, HF low; AF/AE high). Failure to meet this requirement may result in undefined flag states or corrupted data reads. SN74ACT7803-25DL reset is asynchronous to both clocks but requires clock activity to complete-designs must guarantee clock presence during reset assertion.