SN74LS642DWG4 Texas Instruments Integrated Circuit (Small Outline Packages) In Stock
The SN74LS642DWG4 is an 8-bit inverting bidirectional bus transceiver in the LS TTL family, operating from a 5 V supply in a 20-pin wide SOIC package. It provides direction-controlled bidirectional data transfer with active-low output enable, 24 mA sink current per output, and inverted data paths between A and B ports. It is used in data bus isolation, memory interfacing, and backplane buffering in TTL-compatible digital systems.
- Manufacturer
- Texas Instruments
- Package
- Small Outline Packages
- Pin Count
- 20
- Lifecycle
- OBSOLETE
- Datasheet
- SN74LS642DWG4 Datasheet PDF
- Category
- Integrated Circuit
- Temp Range
- ?°C to 70.0°C
- RoHS
- Compliant
- Lead Time
- 3–7 business days
- Shipping
- DHL Express · Worldwide
What are the key features of SN74LS642DWG4?
- 8-bit bidirectional inverting bus transceiver with direction control
- Active-low output enable for bus sharing and isolation
- 24 mA output sink current for driving heavily loaded TTL bus lines
- LS-TTL family compatible with 5 V standard logic levels
- Direction pin for switching between A-to-B and B-to-A data flow
- 20-pin wide SOIC package for automated SMT assembly
What is SN74LS642DWG4 used for?
The SN74LS642DWG4 serves as a bidirectional bus interface between a microprocessor data bus and peripheral devices such as memory banks or I/O expanders, providing signal buffering and bus isolation in 5 V TTL systems. Its inverting data path is used in circuits where polarity inversion is needed to match peripheral logic conventions without additional inverter stages. Legacy industrial controller boards and embedded computing systems with high-capacitance backplane buses rely on its 24 mA drive strength and bidirectional direction control to maintain signal integrity.
What are the specifications of SN74LS642DWG4?
| YTEOL | 0 |
| Additional Feature | WITH DIRECTION CONTROL |
| Control Type | COMMON CONTROL |
| Count Direction | BIDIRECTIONAL |
| Family | LS |
| JESD-30 Code | R-PDSO-G20 |
| JESD-609 Code | e4 |
| Logic IC Type | BUS TRANSCEIVER |
| Max I(ol) | 0.024A |
| Number of Bits | 8 |
| Number of Functions | 1 |
| Number of Ports | 2 |
| Output Characteristics | OPEN-COLLECTOR |
| Output Polarity | INVERTED |
| Package Body Material | PLASTIC/EPOXY |
| Package Equivalence Code | SOP20,.4 |
| Package Shape | RECTANGULAR |
| Package Style | IN-LINE |
| Packing Method | TUBE |
| Peak Reflow Temperature (Cel) | 260 |
| Power Supply Current-Max (ICC) | 95mA |
| Prop. Delay@Nom-Sup | 25ns |
| Propagation Delay (tpd) | 25ns |
| Qualification Status | Not Qualified |
| Supply Voltage-Max (Vsup) | 5.25V |
| Supply Voltage-Min (Vsup) | 4.75V |
| Supply Voltage-Nom (Vsup) | 5V |
| Surface Mount | NO |
| Technology | TTL |
| Temperature Grade | COMMERCIAL |
| Terminal Finish | NICKEL PALLADIUM GOLD |
| Terminal Form | THROUGH-HOLE |
| Terminal Pitch | 2.54mm |
| Terminal Position | DUAL |
| Time@Peak Reflow Temperature-Max (s) | 30 |
| Package | Small Outline Packages |
Compliance & Regulatory
| RoHS Status | Compliant |
| Lead-Free | Yes (Pb-Free) |
| Moisture Sensitivity Level | MSL 1 |
| HTS Code | 8542.39.00.60 |
Where can I find the SN74LS642DWG4 datasheet?
SN74LS642DWG4 Datasheet DownloadOfficial datasheet from Texas Instruments
What are equivalent replacements for SN74LS642DWG4?
Compatible alternatives and drop-in replacements for SN74LS642DWG4:
Frequently Asked Questions
How does the direction pin on SN74LS642DWG4 control data flow?
The DIR pin selects whether data flows from port A to port B or from port B to port A. When DIR is high, data propagates from A to B; when low, the flow reverses. Combined with the active-low output enable, this allows the transceiver to act as a controlled bidirectional bus isolator with 8 bits and 24 mA drive capability per output.
Why does SN74LS642DWG4 invert data, and when is that useful?
The device inverts all 8 data bits as they pass through, so a logic high on an A input appears as a logic low on the corresponding B output and vice versa. This is useful when connecting to peripherals with inverted bus conventions, replacing an additional 74LS04 hex inverter stage and saving one IC package on the board.
What is the output drive capability of SN74LS642DWG4 for bus loading calculations?
Each output can sink up to 24 mA in the low state and source at least 2.6 mA in the high state, following standard LS-TTL drive specifications. On a 5 V backplane this supports driving up to 10 standard TTL loads per output, or equivalent capacitive bus loads typical of 8-bit address and data buses in embedded systems.
Which package does SN74LS642DWG4 use, and how does it differ from the N-suffix DIP variant?
SN74LS642DWG4 comes in a 20-pin wide-body SOIC (300-mil, R-PDSO-G20) for SMT assembly, while the N-suffix variant uses a 20-pin plastic DIP for through-hole boards. The SOIC variant reduces PCB footprint and suits automated pick-and-place production, whereas the DIP suits prototyping or legacy through-hole designs.
For a new 5 V industrial backplane design, should SN74LS642DWG4 be chosen over the 74HC245?
The 74HC245 is non-inverting and offers lower power consumption with faster propagation times below 10 ns at 5 V. SN74LS642DWG4 is the correct choice when the design specifically requires 8-bit inversion together with bidirectional control, or when replacing an LS-family device on an existing board where LS threshold levels and 24 mA drive strength have already been accounted for in termination resistor values.
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About Texas Instruments
Texas Instruments (TI) is a global semiconductor company headquartered in Dallas, Texas. TI designs and manufactures analog and embedded processing chips used in industrial, automotive, consumer, communications, and enterprise systems.
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