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Texas Instruments CD74FCT844AEN
- Part No.:
- CD74FCT844AEN
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
CD74FCT844AEN.pdf
- Description:
- BUS DRIVER, FCT SERIES
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Inventory:1,852
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Product details
Overview
CD74FCT844AEN from Texas Instruments is a BiCMOS 9-bit D-type latch with 3-state outputs, designed for bus-interface buffering and I/O port expansion in TTL-compatible systems. It features inverted outputs, 48-mA sink capability, 3.7-V output voltage swing limitation, and operates across 4.75 V to 5.25 V at 0°C to 70°C - enabling robust drive of high-capacitance buses in industrial control backplanes.
For engineers reviewing the CD74FCT844AEN datasheet, CD74FCT844AEN pinout, CD74FCT844AEN application, or CD74FCT844AEN equivalent, key selection criteria include its BiCMOS-controlled edge rates, SCR latch-up resistance, PRE/CLR asynchronous controls, and OE-gated 3-state behavior during power-up/down transitions.
Technical Context
The CD74FCT844AEN implements a positive-edge transparent latch architecture with independent LE (latch-enable) and OE (output-enable) controls. Its BiCMOS output stage combines bipolar pull-down and CMOS pull-up devices to limit VOH to ~3.7 V (two diode drops below VCC), reducing EMI and supply rail bounce during simultaneous switching.
It integrates active-low asynchronous preset (PRE) and clear (CLR) inputs that override latched data and operate independently of OE state. Input isolation from VCC and buffered inputs ensure noise immunity and compatibility with TTL-level sources while maintaining low quiescent current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | 9-bit D-type latch with inverted 3-state outputs |
| Supply Voltage | 4.75 V to 5.25 V - ensures stable operation within standard 5-V TTL rails |
| Output Sink Current | 48 mA per pin - supports direct drive of heavy capacitive loads without external buffers |
| Output Voltage Swing | Limited to 0 V–3.7 V - suppresses VCC/ground bounce and EMI in dense PCB layouts |
| Propagation Delay | Max 12 ns (LE to Q) - enables reliable timing in 20+ MHz bus cycles |
| Input Clamping | VIK = −1.2 V at −18 mA - protects against negative transients on data/control lines |
| Operating Temperature | 0°C to 70°C - validated for commercial-grade embedded and instrumentation applications |
Pinout & Package
Packaged in 24-pin plastic dual in-line package (PDIP), with 0.6-inch body width and through-hole mounting. Pin pitch is 0.1 inch; lead finish is tin-lead (Pb-containing), per TI's legacy PDIP specification.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2–9, 18–24 | Data inputs (1D–9D), outputs (1Q–9Q), controls (OE, LE, PRE, CLR) | Standardized DIP pinout per TI SCBS728; pins 1–9 = D inputs, 18–24 = Q outputs + controls |
| 1D–9D (pins 2–10) | Asynchronous data inputs | Drive latch inputs directly; buffered for TTL-level compatibility and noise rejection |
| 1Q–9Q (pins 13–21) | Inverted 3-state outputs | Active-low inversion with OE-controlled high-Z state; outputs remain high-Z during power cycling |
| OE (pin 1) | Output enable (active-high) | Places all nine outputs in high-impedance state regardless of LE or data state |
| LE (pin 22) | Latch enable (active-high) | When high: outputs follow inputs; when low: latches and holds last input value |
| PRE (pin 23) | Asynchronous preset (active-low) | Forces outputs high (if OE low); overrides CLR and latch state |
| CLR (pin 24) | Asynchronous clear (active-low) | Forces outputs low (if OE low); overridden by PRE when both asserted |
| VCC (pin 11), GND (pin 12) | Power supply terminals | Single 5-V supply; internal isolation prevents VCC coupling into logic paths |
Key Features
| Feature | Design Value |
|---|---|
| BiCMOS process technology | Combines speed of bipolar with low static power of CMOS - achieves <80 µA ICC at standby |
| Controlled output edge rates | Reduces simultaneous switching noise (SSN) and EMI without external series resistors |
| SCR latch-up resistance | Guaranteed immunity to latch-up under I/O stress per JEDEC JESD78 - critical for hot-swap I/O ports |
| Power-up/power-down high-Z | Outputs default to high-impedance before VCC stabilizes - prevents bus contention during sequencing |
| Input/output isolation from VCC | Eliminates supply-rail coupling into signal paths - improves noise margin in mixed-signal systems |
Applications
| Industrial Backplane Bus Interface | Legacy System I/O Expansion |
|---|---|
Use Scenario: Interfacing microcontroller GPIOs to a 9-bit parallel backplane in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus driver and latch for address/data staging between CPU and peripheral modules. Use Value: 48-mA sink strength drives 100+ pF bus capacitance; 3.7-V swing minimizes ground bounce across shared return paths. |
Use Scenario: Adding parallel I/O capability to an aging 80C51-based test fixture with limited board space. IC Role / Device Role / Timing Role: 9-bit buffer register with asynchronous PRE/CLR for reset-synchronized data capture. Use Value: Inverted outputs match legacy TTL bus polarity; OE-controlled high-Z allows safe insertion into live backplanes. |
| Parity Generation Support | Test Equipment Data Capture |
Use Scenario: Generating odd/even parity bits for memory subsystems in telecom line cards. IC Role / Device Role / Timing Role: Parity-bus interface latch with dedicated PRE/CLR for parity initialization and error recovery. Use Value: PRE overrides CLR to force known parity state on power-up; latch retains parity until next LE pulse. |
Use Scenario: Capturing parallel sensor data streams in automated test equipment with multi-cycle sampling windows. IC Role / Device Role / Timing Role: Synchronized data acquisition latch triggered by system clock edges via LE. Use Value: 12 ns max tpd ensures setup/hold compliance at 20 MHz sampling; 3-state outputs isolate captured data during analysis phase. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 9-bit bus-interface latch applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74FCT844ATPC | Same function, 24-pin SOIC package; RoHS-compliant; identical AC/DC specs | Suitable for surface-mount production; requires PCB redesign from DIP footprint | Select when automated assembly and smaller board area are required |
| 74ACT844PC | CMOS-only process; higher VOH (~4.4 V); no output swing limiting; lower IOL (24 mA) | Higher EMI risk on dense boards; insufficient drive for >50 pF loads | Select only if full-rail VOH and lower static power outweigh EMI and drive constraints |
Compared with SN74FCT844ATPC and 74ACT844PC, the CD74FCT844AEN provides superior EMI suppression and bus-drive capability in through-hole form, making it optimal for prototyping, repair, and legacy system upgrades where DIP packaging and controlled edge rates are essential.
Availability
CD74FCT844AEN is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy I/O expansion, parity generation circuits, and test equipment data capture requiring stable component supply and long-term obsolescence management.
Supply support for CD74FCT844AEN 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 founded in 1930, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The CD74FCT844AEN belongs to TI's FCT logic family - engineered for high-speed, low-noise bus interfacing in 5-V systems where EMI control and legacy compatibility are critical design requirements.
FAQ
What is the operating voltage range for the CD74FCT844AEN?
The CD74FCT844AEN operates over a supply voltage range of 4.75 V to 5.25 V. This tight tolerance ensures compatibility with regulated 5-V TTL systems and prevents malfunction due to rail droop. The device is not rated for 3.3-V operation, and applying voltages outside this range may cause permanent damage or undefined behavior. Always verify VCC stability before enabling LE or OE on the CD74FCT844AEN.
Does the CD74FCT844AEN support hot insertion into a live bus?
Yes - the CD74FCT844AEN enters high-impedance state during power-up and power-down, and its outputs remain high-Z until VCC reaches valid operating levels. Combined with SCR latch-up-resistant BiCMOS design and input clamping (VIK = −1.2 V), this enables safe insertion into energized backplanes. However, OE must be held high during insertion to guarantee output isolation, and bus termination should be verified per system-level ESD requirements for the CD74FCT844AEN.
How does the output voltage swing limitation benefit system design?
The CD74FCT844AEN limits VOH to approximately 3.7 V (two diode drops below VCC), which directly reduces power-bus ringing, VCC bounce, and ground bounce during simultaneous output switching. This feature lowers radiated emissions and improves signal integrity on shared power/ground planes - especially critical in high-density industrial backplanes. Unlike standard TTL or ACT devices, the CD74FCT844AEN achieves this without external damping components, simplifying layout and lowering BOM cost.
What is the functional relationship between PRE, CLR, and OE on the CD74FCT844AEN?
PRE (active-low) and CLR (active-low) are asynchronous controls that override latched data regardless of OE state: PRE forces outputs high (when OE is low), and CLR forces outputs low (when OE is low). PRE takes priority over CLR. OE operates independently - when high, all outputs go high-Z even if PRE or CLR is asserted. The CD74FCT844AEN retains internal latch state during OE high, allowing data retention and re-enabling without reloading.
Is the CD74FCT844AEN pin-compatible with other 9-bit latches like the 74F844?
No - the CD74FCT844AEN is not pin-compatible with the 74F844. While both are 9-bit latches with 3-state outputs, the CD74FCT844AEN uses a different pinout: OE is on pin 1 (not pin 11), and PRE/CLR are on pins 23/24 (not shared with outputs). Additionally, the CD74FCT844AEN has inverted outputs versus non-inverted in 74F844. Substitution requires PCB modification and logic inversion in firmware or external gates to maintain correct functionality for the CD74FCT844AEN.
CD74FCT844AEN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- -
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
CD74FCT844AEN FAQ
1.How can I place an order for CD74FCT844AEN through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74FCT844AEN on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for CD74FCT844AEN reliable?
The price and inventory of CD74FCT844AEN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74FCT844AEN is usually 5 days.
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4.How is shipping managed for CD74FCT844AEN?
CD74FCT844AEN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74FCT844AEN order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for CD74FCT844AEN?
For technical support, including CD74FCT844AEN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74FCT844AEN requirements.
6.How does Aetrix verify that CD74FCT844AEN is sourced from the original manufacturer or authorized distributors?
All CD74FCT844AEN products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that CD74FCT844AEN meets industry standards.
7.What is the process for return or replacement of CD74FCT844AEN?
All CD74FCT844AEN units undergo pre-shipment inspection (PSI). If there is an issue with CD74FCT844AEN, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The CD74FCT844AEN part is unused and in its original packaging.
Return procedure for CD74FCT844AEN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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