Texas Instruments SN74ALS236N

Overview

SN74ALS236N from Texas Instruments is an asynchronous 256-bit first-in, first-out (FIFO) memory IC organized as 64 words × 4 bits, featuring 3-state outputs, data rates up to 30 MHz, and operation over 0°C to 70°C. It serves as a bit-parallel data buffer in bus-matching and rate-adaptation circuits between mismatched clock domains.

For engineers reviewing the SN74ALS236N datasheet, SN74ALS236N pinout, SN74ALS236N application, or SN74ALS236N equivalent, this device is selected for high-speed asynchronous buffering where independent write/read timing, status flag monitoring (IR/OR), and TTL-compatible Schottky logic levels are required.

Technical Context

The SN74ALS236N implements a fully asynchronous FIFO architecture with no internal clock-data shifts in on the rising edge of SI and shifts out on the falling edge of SO. Its 62×4-bit register core supports automatic fall-through when empty and auto-load when full, controlled by IR and OR flags.

It uses advanced low-power Schottky (ALS) technology with noninverting data paths, master reset (RST) initialization, and TTL-compatible input thresholds (VIL = 0.8 V, VIH = 2 V) and output drive (IOL = 24 mA on Q outputs). All timing parameters-including tpd ≤ 1000 ns (SI↓→Q) and tw ≥ 15 ns (pulse width)-are specified at VCC = 4.5–5.5 V.

Key Specifications

Pinout & Package

SN74ALS236N is supplied in a 16-pin plastic dual in-line package (PDIP-N), with 300-mil body width and through-hole mounting. Pin numbering follows standard DIP orientation (pin 1 at top-left corner, notch or dot marking).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ALS236N, SN74AS236N trades higher power for lower latency, while 7200L15P sacrifices integrated status signaling for CMOS efficiency-neither is pin-compatible nor functionally identical, requiring PCB and firmware adaptations.

Availability

SN74ALS236N is available at Aetrix Electronics and suitable for telecom line interface buffering, industrial PLC I/O expansion, legacy bus protocol translation, and test equipment pattern generation requiring stable component supply across long-lifecycle embedded programs.

Supply support for SN74ALS236N 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74ALS236N belongs to TI's legacy 74ALS logic family, designed specifically for high-speed, low-power asynchronous data buffering in 5-V systems where robust TTL compatibility and deterministic handshaking are essential.

FAQ

What is the maximum operating frequency of the SN74ALS236N?

The SN74ALS236N supports data rates up to 30 MHz for both SI and SO inputs, as confirmed by timing requirements in the SDAS107C datasheet. This maximum frequency applies under recommended operating conditions (VCC = 4.5–5.5 V, TA = 0°C to 70°C) and assumes proper signal integrity, including minimum pulse widths of 15 ns for SI, SO, and RST. The actual achievable rate depends on board layout, load capacitance, and power supply stability.

How does the SN74ALS236N handle empty and full FIFO conditions?

The SN74ALS236N uses dedicated status flags: IR (input-ready) goes low when the FIFO is full, preventing further writes; OR (output-ready) goes low when the FIFO is empty, disabling reads. When empty and SI goes low, the latest input word falls through to Q0–Q3 immediately-OR pulses high to indicate validity. When full and SO goes low, IR pulses high to acknowledge auto-load. These flags enable hardware handshaking without external logic.

Is the SN74ALS236N pin-compatible with other 74-series FIFOs like the SN74AS236N?

Yes-the SN74ALS236N and SN74AS236N share identical pinouts, terminal functions, and package options (including N, DW, FN), making them physically interchangeable in PDIP-16 sockets. However, they differ electrically: SN74AS236N has faster propagation delays (≤600 ns) and higher supply current (up to 180 mA), so thermal and timing validation is required before substitution.

What is the role of the RST pin on the SN74ALS236N, and how should it be used at power-up?

The RST pin on the SN74ALS236N is an active-low master reset that initializes the FIFO to empty state: it forces OR low, IR high, and Q0–Q3 to logic low. At power-up, a low-level pulse ≥15 ns must be applied after VCC stabilizes to ensure reliable initialization. If RST is omitted or improperly timed, IR and OR may remain indeterminate, risking data corruption or bus contention during first access.

Does the SN74ALS236N support word-width expansion, and how is it implemented?

Yes-the SN74ALS236N supports word-width expansion as documented in Figure 6 of the SDAS107C datasheet. Three SN74ALS236N devices can be cascaded to form a 192×12-bit FIFO: SI and SO are ganged across all units, while D0–D3 and Q0–Q3 are wired in parallel per 4-bit slice. IR and OR flags remain individual per unit, requiring external OR-gating for composite status. No additional control logic is needed beyond wiring.