Texas Instruments SN74V3640-7PEU

Overview

SN74V3640 from Texas Instruments is a 3.3-V CMOS first-in, first-out (FIFO) memory with 1024 × 36-bit depth, 166-MHz operation (6-ns read/write cycle time), user-selectable ×36/×18/×9 bus sizing, and zero-latency retransmit capability. It serves as a high-speed asynchronous data buffer in network packet processing systems requiring clock domain bridging between mismatched buses.

For engineers reviewing the SN74V3640 datasheet, SN74V3640 pinout, SN74V3640 application, or SN74V3640 equivalent, key selection criteria include its fixed low first-word latency, programmable almost-empty/almost-full flags with eight default offsets, 5-V-tolerant inputs, independent read/write clocks, and support for both standard and first-word fall-through (FWFT) timing modes.

Technical Context

This FIFO implements dual-clock architecture with fully independent WCLK and RCLK domains (0–166 MHz), enabling simultaneous write and read operations without synchronization logic. Its internal RAM array is paired with configurable flag logic, offset registers, and bus-matching control circuitry driven by BM/IW/OW pins during master reset.

The device supports two distinct timing modes: FWFT mode delivers first-word output after three RCLK edges without REN assertion, while standard mode requires explicit REN activation for all reads. Retransmit functionality-configurable for zero-latency or normal-latency behavior via RM pin-is implemented by resetting the read pointer to address zero on RT assertion.

Key Specifications

Pinout & Package

SN74V3640 is housed in a 128-pin Thin Quad Flat Pack (TQFP) package with exposed thermal pad. Pin functions are defined during master reset and remain static thereafter for configuration-critical inputs (e.g., BM, IW, OW, BE, PFM).

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT72V3640 and NB3N502, SN74V3640 uniquely combines 1024 × 36 depth, 166-MHz performance, FWFT timing, zero-latency retransmit, and full bus-matching flexibility - making it the sole option for high-reliability, multi-protocol bridging in infrastructure equipment.

Availability

SN74V3640 is available at Aetrix Electronics and suitable for network packet buffering, video frame synchronization, telecom line card interface, signal processing pipelines, and industrial protocol gateways requiring stable component supply across extended production lifecycles.

Supply support for SN74V3640 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 experience in high-performance memory and interface ICs.

The SN74V3640 belongs to TI's high-speed synchronous FIFO product line, engineered specifically for clock-domain bridging in telecommunications, networking, and digital video systems demanding deterministic latency and flexible bus-width adaptation.

FAQ

What is the memory organization and maximum operating frequency of the SN74V3640?

The SN74V3640 is a 1024 × 36-bit FIFO memory with a maximum operating frequency of 166 MHz, delivering a 6-ns read/write cycle time. This configuration provides 36 Kbits of buffer space optimized for high-throughput data flow in applications such as packet switching and video streaming. The SN74V3640 achieves this performance using submicron CMOS technology and is characterized for commercial temperature range (0°C to 70°C).

How does the SN74V3640 support bus-width conversion between different data paths?

The SN74V3640 supports user-selectable bus sizing via BM, IW, and OW pins during master reset, enabling configurations such as ×36 in to ×18 out, ×36 in to ×9 out, ×18 in to ×36 out, and ×9 in to ×36 out. This allows seamless interface between mismatched subsystems - for example, connecting a 36-bit DSP to an 18-bit microcontroller - without external glue logic. The SN74V3640 also includes big-endian/little-endian selection (BE pin) to ensure correct byte ordering during width conversion.

What distinguishes FWFT mode from standard timing mode in the SN74V3640?

In FWFT mode, the first word written to an empty SN74V3640 appears on Q0–Q35 after exactly three rising edges of RCLK, without requiring REN assertion. Subsequent words still need REN. In standard mode, every read-including the first-requires both REN low and a rising RCLK edge. FWFT mode is selected by asserting FWFT/SI high during master reset and is essential for minimizing latency in burst-mode receivers where immediate data availability is critical.

Can the SN74V3640 be used in systems with mixed 3.3-V and 5-V logic families?

Yes, the SN74V3640 features 5-V-tolerant inputs (D0–D35, WEN, REN, MRS, PRS, etc.), allowing direct connection to 5-V CMOS or TTL outputs while operating from a 3.3-V supply. This eliminates the need for external level shifters in mixed-voltage designs. However, outputs (Q0–Q35) are not 5-V tolerant and must interface only with 3.3-V–compatible receivers. The SN74V3640's OE pin further supports bus sharing by placing outputs in high-impedance state when inactive.

How are the programmable almost-empty and almost-full flags configured in the SN74V3640?

The SN74V3640 provides PAE and PAF flags that can be programmed to assert at any buffer occupancy level using either serial (via FWFT/SI and SEN) or parallel (via D0–D35 and WEN) methods. Eight default offset values are selectable during master reset using FSEL0, FSEL1, and LD. Once configured, these offsets remain retained through partial reset (PRS), enabling dynamic watermark setting without disrupting ongoing operation. The SN74V3640 supports both synchronous and asynchronous timing modes for PAE/PAF via the PFM pin.