Texas Instruments SN74ACT2235-20PAG

Overview

SN74ACT2235-20PAG from Texas Instruments is an asynchronous bidirectional first-in, first-out (FIFO) memory IC with dual 1024 × 9-bit independent FIFOs, 25 ns access time, 50 MHz data rate, and programmable almost-full/almost-empty flags. It integrates bus transceivers and control logic for real-time or stored-data multiplexing in high-speed digital interface buffering applications.

For engineers reviewing the SN74ACT2235-20PAG datasheet, SN74ACT2235-20PAG pinout, SN74ACT2235-20PAG application, or SN74ACT2235-20PAG equivalent, this device supports independent asynchronous read/write clocks (LDCKA/UNCKA, LDCKB/UNCKB), reset-controlled flag initialization, and direct 8 mA/16 mA bus-drive capability without external buffers.

Technical Context

The SN74ACT2235-20PAG implements two physically separate 1024-word × 9-bit FIFO arrays with independent input and output clock domains (LDCKA/UNCKA for FIFO A; LDCKB/UNCKB for FIFO B), enabling true asynchronous data bridging between mismatched timing domains. Each FIFO features dedicated empty/full/half-full flags and user-programmable almost-full/almost-empty offsets via DAF/DBF inputs.

Its integrated dual-directional bus transceiver (A0–A8 ↔ B0–B8) is controlled by SAB/SBA select lines and GAB/GBA enables, eliminating external glue logic for eight defined bus-management functions-including real-time pass-through, FIFO-to-bus, and mixed-mode transfers-while suppressing decoding glitches during mode transitions.

Key Specifications

Pinout & Package

SN74ACT2235-20PAG uses a 64-pin thin quad flat package (TQFP) per JEDEC MS-026, with 0.5-mm lead pitch, 10.2 mm × 10.2 mm body, and exposed thermal pad (non-electrical). Pin 1 marked via corner notch; pins numbered counterclockwise.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT7205L15TPG and MC10E141FN, the SN74ACT2235-20PAG uniquely combines dual asynchronous FIFOs, integrated 5-V bus transceivers, and programmable flags in one 64-pin TQFP-reducing component count and layout complexity for commercial industrial interfaces.

Availability

SN74ACT2235-20PAG is available at Aetrix Electronics and suitable for industrial data acquisition, protocol translation bridges, DSP-to-FPGA interfaces, and legacy bus interfacing requiring stable component supply and long-term obsolescence management.

Supply support for SN74ACT2235-20PAG 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 industrial and automotive ICs.

The SN74ACT2235-20PAG belongs to TI's advanced CMOS logic FIFO family, designed specifically for asynchronous data buffering in mixed-clock-domain systems where deterministic latency, bus compatibility, and minimal external components are critical.

FAQ

What is the maximum operating frequency of the SN74ACT2235-20PAG?

The SN74ACT2235-20PAG supports up to 50 MHz for both LDCKA/LDCKB write clocks and UNCKA/UNCKB read clocks under recommended conditions (VCC = 4.5–5.5 V, TA = 0°C to 70°C). This is verified in the timing requirements table of the SCAS148F datasheet, where t_CLK min = 20 ns corresponds to 50 MHz.

Does the SN74ACT2235-20PAG require external pull-up resistors on its I/O lines?

No, the SN74ACT2235-20PAG does not require external pull-up resistors on A0–A8 or B0–B8. Its Advanced CMOS outputs provide active 16-mA sink and 8-mA source drive, enabling direct connection to TTL/CMOS loads. Pull-ups would interfere with bidirectional operation and violate the specified VOL/VOL limits.

How is the almost-full/almost-empty flag programmed on the SN74ACT2235-20PAG?

The SN74ACT2235-20PAG programs AF/AEA and AF/AEB during reset: assert DAF low to latch A0–A8 as offset X, then cycle RSTA; similarly, use DBF and RSTB for Y. Holding DAF/DBF high during reset selects the default offset of 256. This procedure is detailed in the "Programming Procedure for AF/AEA" section of the datasheet.

Can the SN74ACT2235-20PAG operate with mixed voltage domains (e.g., 3.3-V controller and 5-V bus)?

No-the SN74ACT2235-20PAG is a 5-V-only device (VCC = 4.5–5.5 V) and its I/Os are not 3.3-V tolerant. Driving A0–A8 or B0–B8 with 3.3-V logic violates the VIH = 2.0 V minimum requirement and risks unreliable flag assertion or data corruption. Level translation is required for 3.3-V interfaces.

What is the purpose of the NC pins on the SN74ACT2235-20PAG PAG package?

The SN74ACT2235-20PAG PAG package includes multiple NC (No internal connection) pins-specifically pins 23, 24, 31, 36, 47, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, and 62-as confirmed in the mechanical drawing MTQF006A and terminal function table. These pins must remain unconnected and should not be tied to VCC, GND, or signals.