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Texas Instruments SN74CBT3125DR
- Part No.:
- SN74CBT3125DR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74CBT3125DR.pdf
- Description:
- IC BUS SWITCH 1 X 1:1 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,365
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Product details
Overview
SN74CBT3125DR from Texas Instruments is a quadruple FET bus switch IC with independent 5-Ω bidirectional analog/digital signal paths, TTL-compatible control inputs, and 4.0–5.5 V supply operation. It enables or isolates four A↔B data channels via individual OE pins and is used in high-speed bus isolation, level translation, and hot-swap I/O buffering applications.
For engineers reviewing the SN74CBT3125DR datasheet, SN74CBT3125DR pinout, SN74CBT3125DR application, or SN74CBT3125DR equivalent, key selection criteria include on-state resistance (5–7 Ω), propagation delay (≤0.35 ns at VCC = 4 V), enable/disable timing (≤6 ns/≤5.1 ns), thermal performance (θJA = 86°C/W for SOIC-D), and SOIC-14 package compatibility with legacy '125-type layouts.
Technical Context
The SN74CBT3125DR implements four independent transmission-gate-based FET switches, each controlled by a dedicated output-enable (OE) input operating under positive logic: low OE connects A↔B ports, high OE places the channel in high-impedance state. No internal pull-up or pull-down resistors are integrated; external pull-up to VCC is required for power-up/down high-Z assurance.
Each switch supports bidirectional signal flow with rail-to-rail voltage handling (−0.5 V to 7 V), operates across −40°C to +85°C, and maintains sub-1 ns switching transitions under 50 pF load. The device lacks internal ESD protection beyond standard CMOS levels and requires external clamping for harsh environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.0 V to 5.5 V - Ensures compatibility with 5-V TTL and mixed-voltage systems without level shifters. |
| ron (Typ) | 5 Ω to 7 Ω - Enables low-loss signal routing for data rates up to 500 Mbps with minimal insertion loss. |
| tpd (Max) | 0.35 ns at VCC = 4 V - Supports ultra-fast digital bus switching in high-throughput memory and peripheral interfaces. |
| ten / tdis (Max) | 6 ns / 5.1 ns - Guarantees precise timing control for synchronous bus gating and clock-domain isolation. |
| VIH / VIL | 2.0 V / 0.8 V - Matches standard TTL input thresholds, eliminating need for external logic-level translators. |
| θJA (SOIC-D) | 86°C/W - Defines thermal derating limit for continuous 128 mA per channel in standard PCB layouts. |
| ICC (Max) | 3 μA - Enables ultra-low static power in always-on isolation circuits and battery-backed subsystems. |
Pinout & Package
SN74CBT3125DR uses a 14-pin SOIC (D) package with 1.27 mm pitch, 8.75 mm × 3.91 mm body, and 1.75 mm max height. Pin 1 is located at top-left corner with index marking; pin 7 is GND, pin 14 is VCC.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE, 2OE, 3OE, 4OE | Independent output-enable inputs | Active-low controls for channels 1–4; must be pulled high externally for guaranteed high-Z during power sequencing. |
| 1A–4A, 1B–4B | Bidirectional signal terminals | Paired A/B ports per channel; no directionality-signals pass equally in either direction when enabled. |
| GND (Pin 7) | Power reference ground | Common return path for all switches and control logic; requires low-inductance connection to minimize noise coupling. |
| VCC (Pin 14) | Supply voltage input | Powers both FET channels and control circuitry; bypassing with 0.1 μF ceramic capacitor near pin is mandatory. |
| NC (Pins 1 & 13) | No internal connection | Unbonded die pads; must remain unconnected and unstubbed to avoid parasitic coupling or EMI. |
Key Features
| Feature | Design Value |
|---|---|
| 5-Ω on-state resistance | Minimizes voltage drop and signal distortion across full 0–5 V swing, supporting clean analog and digital signal integrity. |
| Standard '125-type pinout | Enables drop-in replacement of legacy 74LS/HC/HCT125 buffers without PCB redesign or layout changes. |
| TTL-compatible control inputs | Accepts standard 5-V logic levels directly-no external level-shifting circuitry needed for microcontroller or FPGA interface. |
| Independent channel control | Allows selective isolation of individual data lines (e.g., isolate only address bits while keeping data active) for flexible bus management. |
| Rail-to-rail signal handling | Supports signals from −0.5 V to 7 V, enabling use in mixed-supply systems and fault-tolerant I/O protection schemes. |
Applications
| PCI Bus Isolation | Hot-Swap I/O Buffering |
|---|---|
Use Scenario: Isolating PCI add-in card data/address lines from motherboard during insertion/removal to prevent bus contention and system lockup. IC Role / Device Role / Timing Role: Bidirectional bus switch providing nanosecond-scale enable/disable control synchronized with hot-swap controller signals. Use Value: Prevents data corruption and power surges by ensuring zero current flow between mismatched voltage domains during transition states. | Use Scenario: Protecting backplane I/O lines in telecom line cards during live module replacement under full operational load. IC Role / Device Role / Timing Role: Independent channel gate managing signal continuity per lane, coordinated with power sequencing and status monitoring. Use Value: Eliminates need for complex power-rail sequencing hardware by enabling/disabling lanes before voltage ramp-up or shutdown. |
| Memory Address Multiplexing | FPGA I/O Expansion |
Use Scenario: Sharing a single SRAM address bus among multiple controllers (e.g., CPU and DMA engine) using time-division access. IC Role / Device Role / Timing Role: Low-latency analog switch routing address bits only to the active controller while blocking others. Use Value: Reduces board space and routing complexity versus discrete logic solutions, with sub-nanosecond skew across all 4 channels. | Use Scenario: Extending limited FPGA I/O pins to drive multiple peripheral devices (e.g., sensors, displays, UARTs) via shared buses. IC Role / Device Role / Timing Role: Signal path selector enabling dynamic reconfiguration of peripheral connections without FPGA reprogramming. Use Value: Increases system flexibility and reduces BOM count by allowing one FPGA pin set to serve multiple functions through software-controlled switching. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar FET bus switch applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74CBTD3384DR | 8-channel, 3-state outputs with 3.3-V-only operation and higher on-resistance (10 Ω typical). | Designed for 3.3-V systems requiring higher channel density; not suitable for 5-V or mixed-voltage buses. | Select when scaling to 8 channels and operating exclusively at 3.3 V with relaxed ron requirements. |
| 74LVC1G3157DCKR | Single-channel SPDT analog switch, 1.65–5.5 V supply, 10 Ω ron, smaller SC70-6 package. | Used for point-to-point signal routing rather than parallel bus isolation; lacks multi-channel synchronization. | Choose for space-constrained designs needing isolated analog/digital signal selection, not quad-bus management. |
Compared with SN74CBT3125DR, SN74CBTD3384DR offers double channel count but sacrifices 5-V compatibility and low ron, while 74LVC1G3157DCKR provides compact single-channel flexibility at the cost of parallel bus functionality and timing coherence across channels.
Availability
SN74CBT3125DR is available at Aetrix Electronics and suitable for PCI bus isolation, hot-swap I/O buffering, and memory address multiplexing requiring stable component supply and long-term industrial availability.
Supply support for SN74CBT3125DR 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 connectivity technologies, with over 90 years of innovation in industrial, automotive, and communications markets.
The SN74CBT3125DR belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered for high-speed, low-distortion signal routing in legacy and mixed-voltage digital systems where timing precision and signal fidelity are critical.
FAQ
What is the maximum continuous current per channel for the SN74CBT3125DR?
The SN74CBT3125DR supports a maximum continuous channel current of 128 mA per switch. This rating applies under recommended operating conditions (VCC = 4–5.5 V, TA = −40°C to +85°C) and assumes proper PCB thermal design. Exceeding this current may cause thermal runaway or permanent damage due to junction temperature rise beyond safe limits.
Does the SN74CBT3125DR require external pull-up resistors on its OE pins?
Yes, the SN74CBT3125DR requires external pull-up resistors on all OE pins to ensure high-impedance state during power-up and power-down. TI specifies that OE should be tied to VCC through a pull-up resistor, with minimum value determined by the driver's current-sinking capability. Floating OE inputs risk undefined channel states and potential bus contention.
Can the SN74CBT3125DR operate with a 3.3-V supply?
No, the SN74CBT3125DR is not rated for 3.3-V operation. Its recommended VCC range is 4.0 V to 5.5 V, and absolute maximum ratings specify −0.5 V to 7 V. At 3.3 V, the device fails to meet VIH/VIL thresholds and exhibits degraded on-resistance and timing performance. For 3.3-V systems, consider SN74CBTD3384 or LVC-series alternatives.
Is the SN74CBT3125DR pin-compatible with standard 74LS125 or 74HC125 devices?
Yes, the SN74CBT3125DR uses the standard '125-type pinout in SOIC-D, SSOP-DB, and TSSOP-PW packages, matching pin assignments of 74LS125 and 74HC125. However, it replaces tri-state logic buffers with FET switches-offering lower ron and faster switching but no built-in logic inversion or drive strength. PCB layout remains identical, but logic-level interpretation differs.
What is the thermal resistance (θJA) of the SN74CBT3125DR in its SOIC-D package?
The SN74CBT3125DR in SOIC-D (D) package has a specified junction-to-ambient thermal resistance (θJA) of 86°C/W. This value assumes JEDEC-standard 2-layer board test conditions (1-inch² copper pad per lead). Actual thermal performance depends on PCB copper area, airflow, and adjacent heat sources-designers should verify junction temperature using worst-case power dissipation (e.g., 4 × 128 mA × 7 Ω).
SN74CBT3125DR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74CBT
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Bus Switch
- Circuit:
- 1 x 1:1
- Independent Circuits:
- 4
- Current - Output High, Low:
- -
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
SN74CBT3125DR FAQ
1.How can I place an order for SN74CBT3125DR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74CBT3125DR 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 SN74CBT3125DR reliable?
The price and inventory of SN74CBT3125DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74CBT3125DR is usually 5 days.
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SN74CBT3125DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74CBT3125DR 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 SN74CBT3125DR?
For technical support, including SN74CBT3125DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74CBT3125DR requirements.
6.How does Aetrix verify that SN74CBT3125DR is sourced from the original manufacturer or authorized distributors?
All SN74CBT3125DR 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 SN74CBT3125DR meets industry standards.
7.What is the process for return or replacement of SN74CBT3125DR?
All SN74CBT3125DR units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT3125DR, 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 SN74CBT3125DR part is unused and in its original packaging.
Return procedure for SN74CBT3125DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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