Texas Instruments SN74ACT3632-15PQ

Overview

SN74ACT3632-15PQ from Texas Instruments is a clocked bidirectional FIFO memory IC with two independent 512 × 36 SRAM buffers, supporting asynchronous or coincident CLKA/CLKB up to 67 MHz, 11 ns access time, and programmable almost-full/empty flags synchronized per port clock. It serves as a high-speed data bridge between mismatched microprocessor buses in telecom line cards.

For engineers reviewing the SN74ACT3632-15PQ datasheet, SN74ACT3632-15PQ pinout, SN74ACT3632-15PQ application, or SN74ACT3632-15PQ equivalent, key selection criteria include dual-port flag synchronization timing, mailbox-bypass register behavior, FIFO reset sequencing, and PQ-package thermal/mechanical constraints for high-density PCB layouts.

Technical Context

The SN74ACT3632-15PQ implements two fully independent 512-word × 36-bit clocked FIFOs (FIFO1 and FIFO2), each with separate write/read pointers, input-ready (IRA/IRB) and output-ready (ORA/ORB) flags, and two-stage synchronizers for all status flags. CLKA governs FIFO1 writes and FIFO2 reads; CLKB governs FIFO2 writes and FIFO1 reads.

It integrates two 36-bit mailbox registers (Mail1 and Mail2) with dedicated flags (MBF1/MBF2), enabling immediate command handoff without queuing delay. Flag offset registers (X1/Y1 for FIFO1; X2/Y2 for FIFO2) are programmable via port A or loaded from preset values (8, 16, or 64) during RST1/RST2 assertion with FS0/FS1 configuration.

Key Specifications

Pinout & Package

SN74ACT3632-15PQ uses a 132-pin Plastic Quad Flat (PQ) package with 0.65 mm lead pitch, designed for surface-mount assembly and thermal dissipation in multi-layer PCBs. Pin 1 is located at top-left corner (marked by dot); pins numbered counterclockwise.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT3622-15PQ, SN74ACT3632-15PQ adds essential bidirectional flow control and mailbox signaling; compared with SN74ACT3642-15PQ, it trades depth/speed for lower power and tighter PCB footprint-making it optimal for space-constrained telecom edge nodes.

Availability

SN74ACT3632-15PQ is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLC backplanes, and DSP interface designs requiring stable component supply across extended production lifecycles.

Supply support for SN74ACT3632-15PQ 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 SN74ACT3632-15PQ belongs to TI's ACT-family clocked FIFO product line, engineered specifically for deterministic, low-latency bridging between asynchronous digital subsystems in communications and industrial control equipment.

FAQ

What is the function of the MBA and MBB pins on the SN74ACT3632-15PQ?

The MBA (Mailbox A) and MBB (Mailbox B) pins are port-select controls that determine whether data transfers occur with the FIFO memory or the dedicated 36-bit mailbox registers. When MBA is high, port-A operations access Mail2; when MBB is high, port-B operations access Mail1. This enables zero-latency command exchange independent of FIFO queuing. The SN74ACT3632-15PQ uses these pins to decouple control signaling from data streaming, critical in real-time interrupt-driven systems.

How does the SN74ACT3632-15PQ handle asynchronous clock domains between CLKA and CLKB?

The SN74ACT3632-15PQ employs two-stage synchronizer chains on all status flags: IRA, ORA, AFA, AEA are synchronized to CLKA; IRB, ORB, AFB, AEB to CLKB. This design reduces metastability probability when clocks run at different frequencies or phases. The functional block diagram confirms independent pointer tracking per FIFO, ensuring reliable flag assertion even with >100 ppm clock drift. SN74ACT3632-15PQ thus safely bridges domains like 25 MHz Ethernet PHY and 67 MHz processor bus without external synchronizers.

Can the SN74ACT3632-15PQ be used without programming the almost-full/empty offset registers?

Yes-the SN74ACT3632-15PQ supports preset offset values (8, 16, or 64 words) selected via FS0/FS1 during RST1/RST2 assertion. If both FS0 and FS1 are low at reset, the device enters port-A programming mode; otherwise, it loads factory presets. Default operation with preset offsets requires no initialization code, making SN74ACT3632-15PQ suitable for simple buffer applications where fixed threshold behavior suffices.

What is the minimum reset sequence required before using the SN74ACT3632-15PQ?

The SN74ACT3632-15PQ requires four low-to-high transitions on both CLKA and CLKB while RST1 (for FIFO1) or RST2 (for FIFO2) is asserted low. After the rising edge of RST1/RST2, FS0/FS1 are latched for offset selection. Both FIFOs must be reset after power-up before writing data-the SN74ACT3632-15PQ will not accept writes until IRA and IRB go high, which occurs two CLKA/CLKB cycles post-reset.

Is the SN74ACT3632-15PQ pin-compatible with other devices in the same family?

Yes-the SN74ACT3632-15PQ is explicitly documented as pin-to-pin compatible with SN74ACT3622-15PQ (single FIFO) and SN74ACT3642-15PQ (1024-word FIFO), sharing identical 132-pin PQ footprint, power pinout, and signal assignments. This allows direct replacement in existing layouts when upgrading functionality or depth, provided timing margins and thermal constraints are verified for the target application.