Texas Instruments SN74ACT2235-40FN

Overview

SN74ACT2235-40FN from Texas Instruments is a dual asynchronous bidirectional FIFO memory IC with two independent 1024 × 9-bit buffers, 25 ns access time at 50-pF load, programmable almost-full/almost-empty flags, and operation over 0°C to 70°C. It enables real-time and stored data multiplexing in high-speed bus arbitration systems.

For engineers reviewing the SN74ACT2235-40FN datasheet, SN74ACT2235-40FN pinout, SN74ACT2235-40FN application, or SN74ACT2235-40FN equivalent, key selection criteria include its 44-pin PLCC (FN) package, independent A/B clock domains, fall-through time ≤22 ns, and support for 25 MHz maximum clock frequency per port under recommended conditions.

Technical Context

The SN74ACT2235-40FN implements two physically separate 1024 × 9-bit FIFOs with fully independent write (LDCKA/LDCKB) and read (UNCKA/UNCKB) clocks, enabling true asynchronous data rate matching between bus domains. Each FIFO supports flag generation-EMPTY, FULL, HALF-FULL, and programmable AF/AE-with user-defined offset values stored via DAF/DBF control.

Its integrated bus transceiver architecture uses SAB/SBA select inputs and GAB/GBA output enables to perform eight distinct bus-management functions-including real-time pass-through, FIFO-to-bus, and bidirectional stored-data transfer-without external logic or decoding glitches during mode transitions.

Key Specifications

Pinout & Package

SN74ACT2235-40FN uses a 44-pin plastic leaded chip carrier (PLCC, FN package) with J-lead configuration per JEDEC MS-018. Pin 1 is located at the index corner; leads are numbered counterclockwise.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT7205L15TPG and MC100E131FNG, SN74ACT2235-40FN uniquely delivers dual independent FIFOs with integrated transceivers and programmable flags in a 5-V, 44-pin PLCC package-enabling compact, low-component-count solutions for mixed-rate bus bridging without voltage translation or glue logic.

Availability

SN74ACT2235-40FN is available at Aetrix Electronics and suitable for telecom line card buffering, industrial PLC data aggregation, test equipment pattern memory, and legacy bus bridge interface requiring stable component supply across extended production lifecycles.

Supply support for SN74ACT2235-40FN 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 company headquartered in Dallas, Texas, delivering analog, embedded processing, and logic products for industrial, automotive, and communications markets.

The SN74ACT2235-40FN belongs to TI's advanced CMOS logic FIFO family, designed specifically for high-reliability, mixed-clock-domain data buffering in commercial-grade systems where deterministic latency and flag-driven flow control are critical.

FAQ

What is the maximum clock frequency supported by SN74ACT2235-40FN for write and read operations?

The SN74ACT2235-40FN supports up to 25 MHz for both LDCKA/LDCKB (write clocks) and UNCKA/UNCKB (read clocks) under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C). This rating is derived from the 'ACT2235-40 speed grade specified in the timing requirements table, where t_PW (pulse width) min is 14 ns, yielding f_max ≈ 1 / (2 × 14 ns) ≈ 35.7 MHz - conservatively derated to 25 MHz for guaranteed operation with 50-pF load and process variation margin. SN74ACT2235-40FN maintains this performance without external termination or timing compensation.

How does the programmable almost-full/almost-empty flag functionality work in SN74ACT2235-40FN?

The SN74ACT2235-40FN implements programmable AF/AEA and AF/AEB flags using DAF and DBF inputs. During reset, a falling edge on DAF latches A0–A8 as the offset X (0–511); similarly, DBF latches B0–B8 as Y. The flag asserts high when FIFO A contains ≤X or ≥(1024−X) words. Default offset is X = Y = 256 if DAF/DBF remain high during reset. This mechanism allows runtime adjustment of buffer watermarks to balance latency and overflow risk. SN74ACT2235-40FN requires no external configuration memory or firmware to set these thresholds.

Can SN74ACT2235-40FN operate with different supply voltages on its A and B data buses?

No, SN74ACT2235-40FN has a single VCC pin supplying both FIFO cores and transceiver logic; it does not support split-rail or dual-supply operation. All I/O ports (A0–A8, B0–B8) and control signals share the same 4.5 V to 5.5 V supply domain. Level-shifting between disparate voltage buses must be implemented externally using discrete translators or dedicated level-shifters. SN74ACT2235-40FN's design assumes uniform 5-V logic levels across both sides, consistent with its Advanced CMOS process and TTL-compatible input thresholds.

What are the key timing differences between SN74ACT2235-40FN and the faster SN74ACT2235-60FN variant?

Compared to SN74ACT2235-60FN, the SN74ACT2235-40FN exhibits longer propagation delays: t_pd (LDCK↑ to B/A) is 8–24 ns vs. 8–26 ns, and t_pd (UNCK↑ to B/A) is 12–35 ns vs. 12–45 ns. Its maximum clock frequency is 25 MHz versus 16.7 MHz for the -60 variant - reflecting tighter internal timing margins. Both share identical flag behavior, pinout, and functional architecture; the -40 suffix denotes optimized speed binning for mid-range throughput applications where 25 MHz suffices and lower power consumption is preferred. SN74ACT2235-40FN achieves this with reduced ICC (10–400 µA typical) versus -60FN.

Is SN74ACT2235-40FN compatible with modern PCB assembly processes including lead-free reflow?

Yes, SN74ACT2235-40FN in the FN (plastic leaded chip carrier) package is rated for lead-free reflow per JEDEC J-STD-020. Its maximum peak reflow temperature is 260°C for 20–40 seconds, consistent with standard Pb-free solder profiles. The device uses matte tin lead finish and meets RoHS Directive 2011/65/EU requirements. No special prebake or moisture sensitivity handling is required (MSL level 3 per J-STD-020), making SN74ACT2235-40FN suitable for high-volume automated assembly without process modification.