My Inquiry
My Account
Texas Instruments CD74HCT640M
- Part No.:
- CD74HCT640M
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
CD74HCT640M.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:645
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
CD74HCT640M from Texas Instruments is an inverting octal three-state bus transceiver designed for bidirectional asynchronous data transfer between parallel buses in industrial and embedded systems. It operates at 4.5 V to 5.5 V, delivers 6 mA output drive, supports -55°C to +125°C operation, and features buffered inputs with TTL-compatible logic thresholds (VIL = 0.8 V max, VIH = 2 V min).
For engineers reviewing the CD74HCT640M datasheet, CD74HCT640M pinout, CD74HCT640M application, or CD74HCT640M equivalent, this page provides verified functional modes, switching characteristics, thermal metrics, and real-world bus interface design guidance - including DIR-controlled directionality, OE-gated three-state control, and LSTTL load compatibility.
Technical Context
The CD74HCT640M implements dual-directional inverting data flow controlled by a single DIR input: low enables A→B (A inputs inverted to B outputs), high enables B→A (B inputs inverted to A outputs). Its three-state outputs are independently disabled via active-low OE, placing all I/Os in high-impedance mode regardless of DIR state.
It uses silicon-gate CMOS technology with TTL-compatible input thresholds and CMOS-level output swing. Propagation delay is 22–33 ns (A↔B) and 30–38 ns (output enable/disable transitions) at VCC = 4.5 V, CL = 50 pF, and operates reliably across full military temperature range without derating.
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 threshold (VIL/VIH) | 0.8 V (max) / 2.0 V (min) - guarantees reliable recognition of standard TTL logic levels. |
| Output drive (IO) | ±6 mA (TTL loads) - drives up to 15 LSTTL loads per output, supporting large-capacitance backplanes. |
| Propagation delay (tpd) | 22–33 ns (A↔B) - enables synchronous operation in 20+ MHz bus systems with 50 pF loading. |
| Operating temperature | -55°C to +125°C - qualified for aerospace, defense, and under-hood automotive applications. |
| Three-state leakage (IOZ) | ±5 µA (max) - minimizes bus contention current when outputs are disabled. |
| Power dissipation capacitance (Cpd) | 41 pF - used to calculate dynamic power: PD = VCC² × fi × (Cpd + CL). |
Pinout & Package
CD74HCT640M is packaged in a 20-pin SOIC (DW) with 12.80 mm × 7.50 mm body size, 1.27 mm lead pitch, and 2.65 mm maximum height. RoHS-compliant, NIPDAU lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OE) | Active-low output enable | Drives all A/B outputs into high-Z when high; required for bus arbitration and multi-driver systems. |
| 2–9 (An) | Inverting input/output port A | Port A pins function as inputs when DIR = L and B is outputting; act as inverted outputs when DIR = H and B is inputting. |
| 10 (GND) | Ground reference | Common return path for logic and output currents; must be low-impedance to minimize ground bounce. |
| 11–18 (Bn) | Inverting input/output port B | Port B pins mirror An behavior with opposite directionality - inverted outputs when DIR = L, inverted inputs when DIR = H. |
| 19 (DIR) | Data direction control | Low = A→B (An → inverted Bn), High = B→A (Bn → inverted An); determines signal flow path unidirectionally. |
| 20 (VCC) | Positive supply | 4.5–5.5 V rail; requires local 0.1 µF ceramic bypass capacitor placed adjacent to pin for noise suppression. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting bidirectional transceivers | Eight independent A↔B channels with polarity inversion on both directions - eliminates need for external inverters in differential bus designs. |
| TTL-compatible inputs | VIL ≤ 0.8 V and VIH ≥ 2.0 V at VCC = 4.5–5.5 V - interoperates directly with legacy 74LS and 74ALS families without interface logic. |
| High fanout capability | Drives 15 LSTTL loads per output - reduces need for bus repeaters in wide-data-path systems like memory expansion or peripheral interconnects. |
| Wide temperature range | -55°C to +125°C operation - supports deployment in extended-environment applications including avionics, downhole tools, and industrial PLCs. |
| Controlled transition times | 12–15 ns output rise/fall (tt) - limits EMI generation and prevents false triggering on shared bus lines. |
Applications
| Industrial Backplane Interconnect | Legacy System Bus Extension |
|---|---|
Use Scenario: Connecting multiple microcontroller modules to a shared 64-bit data bus in a modular PLC rack. IC Role / Device Role / Timing Role: Bidirectional inverting transceiver enabling isolated read/write cycles between CPU and I/O cards while preventing bus contention. Use Value: DIR pin selects direction per transaction; OE disables outputs during arbitration - eliminates need for external bus buffers or direction-control logic. | Use Scenario: Extending a vintage 8086-based S-100 bus with modern peripherals requiring 5 V TTL signaling. IC Role / Device Role / Timing Role: Level- and polarity-transparent bridge between original LSTTL bus drivers and new CMOS peripherals. Use Value: Matches 74LS640 timing and drive strength while consuming less quiescent current (ICC ≤ 160 µA vs. ~20 mA for LS). |
| Military Data Link Interface | Automotive Engine Control Subsystem |
Use Scenario: Isolating MIL-STD-1553 remote terminal data paths from central bus controller in airborne avionics. IC Role / Device Role / Timing Role: Radiation-tolerant, wide-temp transceiver managing command/data handshaking between redundant processor pairs. Use Value: -55°C to +125°C rating and 15 LSTTL load drive ensure deterministic timing under thermal stress and vibration. | Use Scenario: Interfacing crankshaft position sensor signals and injector driver logic across separate ECU submodules. IC Role / Device Role / Timing Role: Direction-controlled bus isolation block preventing ground-loop coupling between analog sensor and high-current actuator domains. Use Value: Three-state outputs suppress crosstalk during idle periods; inverting logic simplifies signal polarity alignment with existing MCU GPIO mapping. |
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 architecture; identical VCC, IO, and temp range; 25 ns tpd (A→B) at 5 V. | Requires external inverters if system-level polarity inversion is mandatory; otherwise pin-compatible for direction-controlled bidirectional use. | Select when signal inversion is handled upstream/downstream - avoids redesigning logic polarity mapping. |
| CD74HC640M | Same pinout and function but HC variant: 2–6 V supply, higher noise immunity (NIL/NIH = 30%), slower tpd (23–27 ns at 6 V). | Used where mixed-voltage systems exist or where lower power at reduced speed is acceptable; not TTL-input compatible. | Choose for battery-powered or multi-rail designs needing wider supply flexibility and lower ICC (≤ 80 µA typical). |
Compared with SN74HCT245N and CD74HC640M, CD74HCT640M uniquely delivers guaranteed inverting functionality with native TTL input compatibility and military-grade temperature support - making it optimal for legacy-replacement and harsh-environment bus isolation where polarity alignment is fixed in hardware.
Availability
CD74HCT640M is available at Aetrix Electronics and suitable for industrial backplane interconnect, legacy system bus extension, military data link interface, and automotive engine control subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74HCT640M 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 connectivity solutions for industrial, automotive, and communications markets.
The CD74HCT640M belongs to TI's legacy high-speed CMOS logic family, engineered specifically for robust, pin-compatible upgrades of obsolete TTL bus transceivers in mission-critical and extended-temperature applications.
FAQ
What is the logic function of CD74HCT640M?
The CD74HCT640M is an octal inverting three-state bus transceiver. It routes data bidirectionally between two 8-bit buses (A and B) with inversion on both paths. Direction is set by the DIR pin (low = A→B, high = B→A), and outputs are enabled/disabled by the active-low OE pin. All outputs go high-impedance when OE is high, regardless of DIR state.
Does CD74HCT640M support 3.3 V operation?
No, CD74HCT640M does not support 3.3 V operation. Its recommended supply voltage is strictly 4.5 V to 5.5 V. For 3.3 V systems, consider the CD74HC640M (2–6 V) or SN74LVC245A (1.65–3.6 V), though neither offers identical inverting functionality or TTL input compatibility.
How is the direction control implemented in CD74HCT640M?
Direction control in CD74HCT640M is managed solely by the DIR pin. When DIR = low, data flows from port A to port B with inversion (An → !Bn). When DIR = high, data flows from port B to port A with inversion (Bn → !An). This unidirectional control per transaction eliminates bus turnaround delays found in half-duplex protocols.
What is the maximum capacitive load CD74HCT640M can drive?
CD74HCT640M is characterized for CL = 50 pF in switching specifications, with propagation delay increasing predictably beyond that. Its ±6 mA output drive supports up to 15 LSTTL loads - equivalent to ~450 pF total bus capacitance assuming standard 30 pF per LSTTL input. For heavier loads, verify timing margins using the provided tpd vs. CL curves.
Is CD74HCT640M pin-compatible with CD74HC640M?
Yes, CD74HCT640M and CD74HC640M share identical 20-pin SOIC (DW) packaging, pinout, and functional block diagram. They differ only in electrical specifications: CD74HCT640M has TTL-compatible inputs and 4.5–5.5 V operation, while CD74HC640M uses CMOS inputs and 2–6 V operation. Swapping requires verifying supply voltage and input source compatibility.
CD74HCT640M Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- 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:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
CD74HCT640M FAQ
1.How can I place an order for CD74HCT640M through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HCT640M 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 CD74HCT640M reliable?
The price and inventory of CD74HCT640M are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT640M is usually 5 days.
3.What payment methods are accepted for CD74HCT640M?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT640M transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HCT640M?
CD74HCT640M orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HCT640M 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 CD74HCT640M?
For technical support, including CD74HCT640M datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT640M requirements.
6.How does Aetrix verify that CD74HCT640M is sourced from the original manufacturer or authorized distributors?
All CD74HCT640M 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 CD74HCT640M meets industry standards.
7.What is the process for return or replacement of CD74HCT640M?
All CD74HCT640M units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT640M, 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 CD74HCT640M part is unused and in its original packaging.
Return procedure for CD74HCT640M:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
CD74HCT640M Tags
-
SN74LVC1G17DBVR
Texas Instruments
-
SN74LVC1G07DCKR
Texas Instruments
-
SN74LVC1G17DCKR
Texas Instruments
-
SN74LVC1G07DBVR
Texas Instruments
-
SN74LVC1G125DCKR
Texas Instruments
-
SN74AHCT1G126DBVR
Texas Instruments
-
SN74LVC1G125DBVR
Texas Instruments
-
SN74AHCT1G125DBVR
Texas Instruments
-
SN74LVC2G17DBVR
Texas Instruments
-
SN74LVC2G07DCKR
Texas Instruments
-
SN74LVC1G34DCKR
Texas Instruments
-
SN74LVC2G17DCKR
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
