Texas Instruments CD74HCT4515EN

Overview

CD74HCT4515EN from Texas Instruments is a 4-line to 16-line decoder/demultiplexer with input latches, designed for address decoding and data routing in digital systems. It operates from 4.5 V to 5.5 V, features latch-enable control (LE), active-low enable (E), and outputs low when selected - distinguishing it from the CD74HCT4514 which outputs high. It supports industrial temperature range (–55°C to 125°C) and is used in memory address selection and I/O port expansion.

For engineers reviewing the CD74HCT4515EN datasheet, CD74HCT4515EN pinout, CD74HCT4515EN application, or CD74HCT4515EN equivalent, key selection criteria include latch-controlled input sampling, active-low output polarity, 16-channel demux capability, and compatibility with LSTTL/CMOS logic levels at 5 V.

Technical Context

The CD74HCT4515EN integrates a 4-bit strobed latch followed by a 4-to-16 line decoder. Input latching occurs on LE high-to-low transition, freezing A0–A3 values for stable decoding independent of subsequent input changes. The E input serves dual roles: as an enable/disable control for output selection and as the data input during demultiplexing mode.

Its output logic is active-low - only one Y0–Y15 goes low per valid A0–A3 combination when E is low; all outputs go high when E is high. Propagation delays are balanced (tpd = 55 ns typ. at VCC = 4.5 V, CL = 50 pF), and transition times are tightly controlled (tt = 19 ns typ.), supporting reliable timing in synchronous digital systems.

Key Specifications

Pinout & Package

CD74HCT4515EN is housed in a 24-pin plastic dual-in-line package (PDIP), JEDEC MS-010 compliant, with 0.300-inch body width and through-hole mounting.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar decoder/demultiplexer applications.

Compared with SN74HCT154N, CD74HCT4515EN adds critical latch control for volatile address buses; versus CD74HCT4514EN, it delivers complementary active-low output behavior essential for direct interface with /CS or /OE inputs requiring low-level activation.

Availability

CD74HCT4515EN is available at Aetrix Electronics and suitable for memory decoding, I/O expansion, industrial control logic, and automated test equipment requiring stable component supply across extended temperature ranges.

Supply support for CD74HCT4515EN 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 CD74HCT4515EN belongs to TI's HCT logic family - designed for 5 V mixed-signal systems requiring LSTTL compatibility, low power, and extended temperature operation without sacrificing speed.

FAQ

What is the function of the LE pin on the CD74HCT4515EN?

The LE (Latch Enable) pin on the CD74HCT4515EN controls input sampling: when LE is high, the A0–A3 address inputs pass through transparently to the decoder; when LE transitions low, the current A0–A3 values are latched and held, allowing address stability even if inputs change afterward. This prevents glitches during bus arbitration or asynchronous address updates - a key differentiator from non-latching decoders like the SN74HCT154N. The CD74HCT4515EN relies on this behavior for reliable operation in microprocessor bus interfaces.

How does the CD74HCT4515EN differ from the CD74HCT4514EN?

The CD74HCT4515EN and CD74HCT4514EN share identical pinout, timing, and electrical specs - differing solely in output polarity. When enabled (E = low) and a valid address is latched, CD74HCT4515EN drives the selected Yx output low while others remain high; CD74HCT4514EN drives the selected output high. This makes CD74HCT4515EN ideal for asserting /CS or /OE signals, whereas CD74HCT4514EN suits active-high enable schemes. Both use the same CD74HCT4515EN package and operate across –55°C to 125°C.

Can the CD74HCT4515EN be used as a demultiplexer?

Yes, the CD74HCT4515EN functions as a 1-to-16 demultiplexer by using the E input as the serial data line and A0–A3 as the 4-bit channel select address. When E is low, the data (low) appears on the selected Yx output; when E is high, all outputs go high - effectively disabling the channel. This eliminates external AND gates needed in basic demux implementations. The latch feature further allows data to be held steady during address transitions, making CD74HCT4515EN especially useful in time-critical routing applications such as test equipment signal switching.

What is the maximum fanout capability of the CD74HCT4515EN outputs?

The CD74HCT4515EN outputs support up to 10 LSTTL loads over the full operating temperature range (–55°C to 125°C), verified per TI's SCHS314C datasheet. This fanout rating reflects the device's ability to drive standard TTL inputs while maintaining valid VOH/VOL levels and timing margins. At 25°C, drive strength increases slightly, but design margin should be based on the worst-case 10-load spec. For higher fanout, buffer stages are recommended - particularly when driving long traces or multiple inputs. The CD74HCT4515EN's ±25 mA per-output rating supports direct interface with many discrete loads without added buffering.

Is the CD74HCT4515EN compatible with 3.3 V logic systems?

No, the CD74HCT4515EN is not 3.3 V compatible: its absolute minimum VCC is 4.5 V, and input thresholds (VIH ≥ 2 V, VIL ≤ 0.8 V) are optimized for 5 V operation. Driving its inputs from 3.3 V logic may result in marginal or invalid high-level recognition, especially over temperature. For 3.3 V systems, consider TI's SN74LVC138A or similar LVCMOS-compatible decoders. The CD74HCT4515EN must be powered from a regulated 5 V supply and interfaced only with 5 V–tolerant logic families - a constraint critical for mixed-voltage board designs.