Texas Instruments CD74HC40105MT

Overview

CD74HC40105MT from Texas Instruments is a high-speed CMOS 4-bit × 16-word first-in-first-out (FIFO) elastic storage register with independent asynchronous input/output control, three-state outputs, and master reset functionality. It operates from 2V to 6V, supports -55°C to +125°C, and delivers ripple-through delay of 400 ns (typ.) at 4.5V for SI-to-Qn transfer - enabling reliable buffering between mismatched clock domains in data acquisition and communications systems.

For engineers reviewing the CD74HC40105MT datasheet, CD74HC40105MT pinout, CD74HC40105MT application, or CD74HC40105MT equivalent, key selection criteria include its 16-word depth, independent shift-in/shift-out timing, DIR/DOR status flag logic, SOIC-16 package compatibility, and HC-series voltage flexibility versus HCT-series TTL-level input compatibility.

Technical Context

The CD74HC40105MT implements a marker-bit–based control architecture where each of 16 positions uses a flip-flop to track occupancy ('1' = filled, '0' = vacant), enabling automatic data rippling without external address management. Its DIR and DOR flags are buffered outputs of the first and last control flip-flops, respectively, providing real-time full/empty status.

Shift-in is edge-triggered on SI (low-to-high), while shift-out is edge-triggered on SO (negative-going); both operate independently of the three-state output enable (OE). The master reset (MR) clears all marker bits but preserves stored data values until overwritten - distinguishing it from full register clearing.

Key Specifications

Pinout & Package

CD74HC40105MT is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package with standard 1.27 mm pitch, JEDEC MS-012AC compliant, and RoHS-compliant NIPDAU lead finish. Thermal resistance θJA = 73°C/W enables stable operation under moderate power dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HCT40105MT and SN74ACT2227N, the CD74HC40105MT offers broader supply voltage flexibility and simpler hardware handshaking via dedicated DIR/DOR pins, making it optimal for mixed-voltage, resource-constrained designs requiring minimal external logic.

Availability

CD74HC40105MT is available at Aetrix Electronics and suitable for CPU buffering, radar data acquisition, bit-rate smoothing, and industrial communications systems requiring stable component supply across extended temperature ranges.

Supply support for CD74HC40105MT 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 delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The CD74HC40105MT belongs to TI's High-Speed CMOS Logic family, designed specifically for asynchronous data buffering and clock-domain isolation in mission-critical systems where reliability, wide temperature operation, and low power are essential.

FAQ

What is the maximum operating frequency of the CD74HC40105MT?

The CD74HC40105MT supports a maximum SI/SO pulse frequency of 12 MHz over the full -55°C to +125°C range at 4.5V supply. At 6V and 25°C, this increases to 18 MHz. These limits are defined by minimum pulse widths (e.g., 20 ns for SI at 4.5V) and propagation delays, not by internal oscillator constraints - the device is purely asynchronous and clocked only by external SI/SO edges.

Does the CD74HC40105MT clear stored data during Master Reset (MR)?

No, the CD74HC40105MT does not clear stored data during Master Reset. MR resets only the control logic marker bits to '0', setting DIR HIGH and DOR LOW. The actual data bits in the 16-word register remain unchanged and will be superseded only upon the next successful SI pulse. This behavior preserves data integrity in partial-reset scenarios where content retention is critical.

Can the CD74HC40105MT be used in a 3.3V system?

Yes, the CD74HC40105MT is fully specified for 2V to 6V operation, including 3.3V. At 3.3V, VIH is guaranteed ≥2.31V and VIL ≤1.0V, ensuring robust noise margins against typical 3.3V logic families. Input leakage remains ≤±1 µA, and propagation delays increase predictably (e.g., SI-to-Qn ≤ 450 ns max), making it suitable for mixed-signal FPGA or ARM-based designs.

How does the CD74HC40105MT indicate FIFO full and empty states?

The CD74HC40105MT uses two open-drain status flags: DIR (pin 2) goes LOW when all 16 positions are filled - indicating FIFO full; DOR (pin 15) goes LOW when no valid data remains - indicating FIFO empty. Both flags are active-HIGH and require external pull-up resistors. Their states reflect real-time occupancy derived from the marker-bit chain, not sampled registers.

Is the CD74HC40105MT pin-compatible with the CD40105B?

The CD74HC40105MT is functionally compatible with the CD40105B except for shift-out circuitry - the HC version decouples SO from OE control, eliminating the CD40105B's restriction that OE must remain HIGH during SO transitions. Pinout and package are identical (SOIC-16), but electrical characteristics differ: HC offers higher speed, lower power, and wider voltage range versus the older CD40105B's 3V–18V range and slower timing.