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Texas Instruments CD74HCT640E
- Part No.:
- CD74HCT640E
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
CD74HCT640E.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:536
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Product details
Overview
CD74HCT640E from Texas Instruments is an inverting octal three-state bus transceiver designed for bidirectional asynchronous data transfer between parallel buses in industrial and military-grade systems. It operates at 4.5 V to 5.5 V, supports -55°C to +125°C temperature range, delivers 6 mA output drive at VOH = 3.98 V (min), and features buffered inputs with TTL-compatible logic thresholds (VIL = 0.8 V max, VIH = 2 V min).
For engineers reviewing the CD74HCT640E datasheet, CD74HCT640E pinout, CD74HCT640E application, or CD74HCT640E equivalent, this page provides verified functional modes, switching characteristics (tpd = 22 ns max A→B at 4.5 V), thermal metrics (RθJA = 69°C/W), and real-world bus interface design guidance - all confirmed against TI's SCHS192C production data sheet.
Technical Context
The CD74HCT640E implements dual-directional inverting data flow controlled by DIR input and three-state output enable via OE (active-low). Its CMOS silicon-gate architecture ensures LSTTL input compatibility while maintaining low ICC (≤160 µA over full temperature range) and high noise immunity (NIL/NIH = 30% of VCC at 5 V).
Propagation delay is symmetric for A→B and B→A paths (22 ns max at 4.5 V, -40°C to +85°C), with matched transition times (tt = 15 ns max) and tightly controlled output capacitance (CO = 20 pF). The device drives up to 15 LSTTL loads and supports bus hold via external termination per TI's functional mode guidelines.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures direct drop-in replacement for 5 V LSTTL systems without level-shifting. |
| Input Thresholds | VIL ≤ 0.8 V, VIH ≥ 2.0 V - guarantees reliable recognition of standard TTL logic levels. |
| Output Drive | ±6 mA at VOH/VOL - sufficient to drive 15 LSTTL loads on shared bus lines. |
| Propagation Delay | 22 ns max (A→B, 4.5 V, -40°C to +85°C) - enables stable operation in high-speed bus arbitration timing windows. |
| Operating Temperature | -55°C to +125°C - qualified for extended-range industrial, aerospace, and defense applications. |
| Three-State Leakage | ±10 µA max (VO = VCC/GND, -55°C to +125°C) - minimizes bus contention current during high-impedance state. |
| Power Dissipation Cap. | Cpd = 41 pF - used to calculate dynamic power: PD = VCC² × fi × (Cpd + CL). |
Pinout & Package
CD74HCT640E is housed in a 20-pin plastic dual in-line package (PDIP-N), with 25.40 mm × 6.35 mm body size and through-hole mounting compatibility. Pin spacing is 2.54 mm, and lead finish is NiPdAu (RoHS-compliant).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A-side inputs (A1–A8) | Inverted data inputs routed to B outputs when DIR = L and OE = L. |
| 9 | GND | Ground reference for all internal circuitry and I/O terminals. |
| 10, 11, 13, 14, 15, 16, 17, 18 | B-side outputs (B1–B8) | Inverted outputs driven from A inputs (DIR = L) or from B inputs (DIR = H); high-Z when OE = H. |
| 12 | OE | Active-low output enable - controls three-state behavior of all eight B outputs. |
| 19 | DIR | Data direction control - L enables A→B flow; H enables B→A flow (inverting). |
| 20 | VCC | Positive supply rail (4.5–5.5 V) powering internal logic and output drivers. |
Key Features
| Feature | Design Value |
|---|---|
| LSTTL input compatibility | VIL ≤ 0.8 V and VIH ≥ 2.0 V at VCC = 4.5–5.5 V - eliminates need for external level shifters in mixed-logic systems. |
| Symmetric propagation delay | tpd(A→B) = tpd(B→A) ≤ 22 ns - ensures deterministic timing in bidirectional bus arbitration protocols. |
| High-noise immunity | NIL = NIH = 30% of VCC at 5 V - suppresses false triggering from EMI or crosstalk in noisy industrial environments. |
| Low quiescent current | ICC ≤ 160 µA over -55°C to +125°C - reduces standby power in battery-backed or thermally constrained systems. |
| Three-state output control | Single OE pin disables all eight B outputs simultaneously - simplifies bus contention management in multi-master architectures. |
Applications
| Industrial Backplane Bus | Military Data Link Interface |
|---|---|
|
Use Scenario: Bidirectional data exchange between processor and peripheral modules across a 20 cm, 150 pF backplane trace. IC Role / Device Role / Timing Role: Inverting bus transceiver enabling isolated A↔B communication with direction control (DIR) and bus release (OE). Use Value: 22 ns max tpd and 15 LSTTL drive capability ensure signal integrity and timing margin compliance under worst-case trace loading and temperature extremes. |
Use Scenario: Secure, radiation-tolerant inter-module communication in airborne avionics chassis operating from -55°C to +125°C. IC Role / Device Role / Timing Role: High-reliability octal transceiver managing time-critical sensor-to-processor data handshaking with three-state isolation. Use Value: Extended temperature qualification and ±10 µA high-Z leakage support fault-tolerant bus arbitration in safety-critical flight control subsystems. |
| Test Equipment Bus Controller | Legacy System Bus Bridge |
|
Use Scenario: Programmable logic-controlled data routing between DUT interface and measurement ASIC in automated test equipment. IC Role / Device Role / Timing Role: Direction-configurable inverting buffer synchronizing burst-mode transfers with precise OE timing control. Use Value: Matched A→B/B→A delays and 15 LSTTL fanout allow deterministic setup/hold timing across multiple parallel channels without skew compensation. |
Use Scenario: Interfacing modern microcontroller peripherals to legacy 8-bit ISA-style expansion slots requiring inverted bus signaling. IC Role / Device Role / Timing Role: Logic-level translator and bus driver preserving original system timing while replacing obsolete TTL transceivers. Use Value: Direct TTL input compatibility and 5 V operation eliminate redesign effort, while 69°C/W RθJA supports convection-cooled enclosure layouts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT245N | Non-inverting topology; identical VCC, temperature, and drive specs; 8-bit unidirectional (A→B only) unless paired. | Requires external inversion logic or dual-device configuration for true bidirectional inverting operation. | Select when system-level inversion is handled upstream or when unidirectional throughput dominates design requirements. |
| CD74HC640E | Same pinout and function but HC variant: 2–6 V operation, higher VIH/VIL thresholds (VIH = 3.15 V min @ 4.5 V), no TTL input compatibility. | Not suitable for direct LSTTL interfacing; requires clean 5 V supply and CMOS-level drivers. | Choose for lower-power, wider-supply applications where TTL compatibility is unnecessary and voltage flexibility is critical. |
Compared with SN74HCT245N and CD74HC640E, CD74HCT640E uniquely combines true bidirectional inverting operation, guaranteed LSTTL input compatibility, and military-grade temperature range in a single PDIP package - making it irreplaceable for legacy bus upgrades and harsh-environment data path isolation.
Availability
CD74HCT640E is available at Aetrix Electronics and suitable for industrial backplane buses, military data link interfaces, automated test equipment controllers, and legacy system bus bridges requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74HCT640E 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 logic families.
CD74HCT640E belongs to TI's CDx4HCT logic series, engineered specifically for robust, pin-compatible replacements of legacy TTL bus transceivers in demanding industrial and defense applications.
FAQ
What is the maximum propagation delay of CD74HCT640E under industrial temperature conditions?
The CD74HCT640E exhibits a maximum propagation delay of 28 ns for A→B or B→A paths when operated at 4.5 V over the -40°C to +85°C range, as specified in Section 5.5 of TI's SCHS192C datasheet. This value includes process, voltage, and temperature variation margins and is measured with CL = 50 pF and input rise/fall time ≤ 500 ns.
Does CD74HCT640E support true bidirectional data flow without external logic?
Yes, CD74HCT640E supports true bidirectional inverting data flow using its dedicated DIR pin: when DIR = L, data flows A→B (inverted); when DIR = H, data flows B→A (inverted). OE independently places all B outputs in high-impedance state. No external inverters or direction-control logic are required for basic operation.
Can CD74HCT640E be used with a 3.3 V microcontroller interface?
No - CD74HCT640E requires 4.5 V to 5.5 V supply and is not 3.3 V tolerant. Its VIH minimum is 2.0 V, but input thresholds are optimized for 5 V LSTTL compatibility. For 3.3 V systems, use CD74HC640E (2–6 V) with appropriate level translation or select a 3.3 V–compatible transceiver such as SN74LVC245A.
What is the recommended bypass capacitor for CD74HCT640E?
Texas Instruments recommends a 0.1 µF ceramic bypass capacitor placed as close as possible to the VCC pin (Pin 20) and GND (Pin 9) of CD74HCT640E. For enhanced noise suppression, a parallel 1 µF capacitor may be added - both must be low-ESR types and mounted within 5 mm of the IC leads per Section 8 of the datasheet.
Is CD74HCT640E RoHS compliant and lead-free?
Yes, CD74HCT640E is RoHS compliant with NiPdAu (nickel-palladium-gold) lead finish, as confirmed in TI's PACKAGE OPTION ADDENDUM (July 2022 revision). It meets JEDEC J-STD-020 moisture sensitivity Level-1 rating and is suitable for standard reflow profiles without special handling requirements.
CD74HCT640E Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Logic Type:
- Transceiver, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 6mA, 6mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
CD74HCT640E FAQ
1.How can I place an order for CD74HCT640E through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HCT640E 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 CD74HCT640E reliable?
The price and inventory of CD74HCT640E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT640E is usually 5 days.
3.What payment methods are accepted for CD74HCT640E?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT640E transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HCT640E?
CD74HCT640E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HCT640E 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 CD74HCT640E?
For technical support, including CD74HCT640E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT640E requirements.
6.How does Aetrix verify that CD74HCT640E is sourced from the original manufacturer or authorized distributors?
All CD74HCT640E 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 CD74HCT640E meets industry standards.
7.What is the process for return or replacement of CD74HCT640E?
All CD74HCT640E units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT640E, 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 CD74HCT640E part is unused and in its original packaging.
Return procedure for CD74HCT640E:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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