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Texas Instruments SN74CBT3125DBR
- Part No.:
- SN74CBT3125DBR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 14-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
SN74CBT3125DBR.pdf
- Description:
- IC BUS SWITCH 1 X 1:1 14SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,750
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Product details
Overview
SN74CBT3125DBR from Texas Instruments is a quadruple FET bus switch 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 in high-speed digital interconnects, memory expansion, and level-shifting applications where low on-resistance and fast switching are critical.
For engineers reviewing the SN74CBT3125DBR datasheet, SN74CBT3125DBR pinout, SN74CBT3125DBR application, or SN74CBT3125DBR equivalent, key selection criteria include on-state resistance (5–7 Ω), propagation delay (0.25–0.35 ns), enable/disable timing (1.6–6 ns), thermal resistance (96°C/W), and SSOP-14 package compatibility with legacy '125-type layouts.
Technical Context
This device implements four independent NMOS pass-gate switches controlled by active-low OE inputs. Each switch connects its A and B terminals when OE is low (L), presenting <7 Ω on-resistance and <4 pF off-capacitance - optimized for minimal signal distortion in 3.3 V/5 V mixed-voltage systems.
It operates without internal level shifters or charge pumps; logic thresholds (VIH = 2 V, VIL = 0.8 V) ensure direct interfacing with TTL and CMOS drivers. Power-up/down high-impedance safety requires external pull-up resistors on OE pins to VCC, as no internal biasing is provided.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage (VCC) | 4.0–5.5 V - supports both 5 V legacy and 4 V minimum industrial rails without level translation. |
| On-State Resistance (ron) | 5–7 Ω at 30–64 mA - ensures <350 mV voltage drop under typical 5 V bus loading, preserving signal integrity. |
| Propagation Delay (tpd) | 0.25–0.35 ns - enables sub-nanosecond signal routing in high-speed address/data buses up to 1 GHz effective bandwidth. |
| Enable/Disable Time (ten/tdis) | 1.6–6 ns - guarantees clean channel isolation during clock domain crossing or power sequencing. |
| Off-Capacitance (Cio(OFF)) | 4 pF - minimizes crosstalk and capacitive loading on adjacent traces in dense PCB layouts. |
| Input Clamp Current (IK) | −50 mA - allows safe handling of transient overvoltage events up to −0.5 V on I/O pins. |
| Thermal Resistance (θJA) | 96°C/W (SSOP-DB) - defines maximum power dissipation (≤52 mW at ΔT = 5°C) for continuous operation at 85°C ambient. |
Pinout & Package
SN74CBT3125DBR uses a 14-pin SSOP (Shrink Small Outline Package) with 0.65 mm pitch, 7.4 mm × 5.3 mm body, and 1.75 mm max height - compatible with standard SOIC footprints but requiring tighter trace spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 4, 7, 10 | OE (Output Enable) | Active-low control per channel; must be pulled to VCC via external resistor for guaranteed high-Z at power-up. |
| 2, 5, 12, 14 | A Port | Input/output terminal for first side of each bidirectional switch; electrically identical to B port. |
| 3, 6, 11, 13 | B Port | Input/output terminal for second side of each bidirectional switch; supports true analog/digital signal pass-through. |
| 8 | GND | Ground reference for all switch channels and control logic; requires low-inductance connection to minimize noise coupling. |
| 14 | VCC | Single positive supply for both switch FETs and control circuitry; decoupling capacitor (0.1 µF) required near pin. |
Key Features
| Feature | Design Value |
|---|---|
| Quadruple independent switches | Four isolated A↔B paths allow concurrent routing of separate data/address lines without interference. |
| 5-Ω on-resistance | Enables low-loss signal transmission across 5 V buses with <1% attenuation at 100 mA load current. |
| TTL-compatible inputs | Accepts standard 0.8 V / 2.0 V logic thresholds - eliminates need for external level translators when driving from 5 V microcontrollers. |
| Standard '125 pinout | Direct replacement for legacy 74LS125/74ALS125 in existing SSOP-14 layouts, reducing redesign effort. |
| Low off-capacitance | 4 pF between A/B and GND when disabled - preserves signal rise/fall times in >100 MHz digital interfaces. |
Applications
| Memory Expansion Interface | PCI/ISA Bus Isolation |
|---|---|
Use Scenario: Adding SRAM or Flash memory to an MCU with limited address/data pins by time-multiplexing shared bus lines. IC Role / Device Role / Timing Role: Bidirectional bus switch enabling dynamic routing of address and data signals between CPU and multiple memory banks. Use Value: Eliminates need for tristate buffers or complex glue logic while maintaining signal integrity through 5 Ω RON and sub-ns propagation delay. | Use Scenario: Isolating legacy PCI or ISA peripheral slots from main system bus during hot-plug or fault conditions. IC Role / Device Role / Timing Role: Channel-level disconnect switch controlled by system management logic to prevent back-driving or contention. Use Value: Provides nanosecond-scale enable/disable response (1.6–6 ns) and 4 pF off-capacitance to avoid signal reflection or timing skew. |
| Level-Shifting Data Path | Test Access Multiplexer |
Use Scenario: Interfacing 3.3 V FPGA I/O to 5 V sensor or actuator subsystems without dedicated level translators. IC Role / Device Role / Timing Role: Passive bidirectional voltage translator leveraging inherent FET threshold behavior and rail-referenced control inputs. Use Value: Supports mixed-voltage operation with no external bias components, relying on 4–5.5 V VCC and TTL-compatible OE thresholds. | Use Scenario: Routing JTAG or boundary-scan test signals between multiple ASICs on a single board using shared debug header. IC Role / Device Role / Timing Role: Signal multiplexer enabling one test controller to sequentially access four independent scan chains. Use Value: Guarantees high-impedance isolation between unselected chains (4 pF Cio(OFF)) and avoids signal degradation via 5 Ω RON. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar FET bus switch applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74CBTD3384DBR | 8-channel, higher Ron (7–9 Ω), supports 3.3 V only (VCC = 2.3–3.6 V) | Suitable for low-voltage embedded systems but incompatible with 5 V buses | Select when operating exclusively at 3.3 V and requiring double channel count in same SSOP-24 footprint. |
| 74LVC1G3157DCKR | Single-channel, lower Ron (3–5 Ω), 1.65–5.5 V VCC, SC70-6 package | Requires four discrete units for quad functionality; smaller footprint but higher assembly cost | Choose for space-constrained designs needing highest performance per channel, accepting increased layout complexity. |
Compared with SN74CBT3125DBR, SN74CBTD3384DBR offers more channels at the expense of voltage range and on-resistance, while 74LVC1G3157DCKR delivers superior per-channel specs in a non-integrated form factor - making SN74CBT3125DBR optimal for cost-sensitive, 5 V-compatible quad-switch applications with standard SSOP-14 layout constraints.
Availability
SN74CBT3125DBR is available at Aetrix Electronics and suitable for memory expansion, bus isolation, level-shifting interfaces, and test access multiplexing requiring stable component supply across industrial temperature ranges (−40°C to 85°C).
Supply support for SN74CBT3125DBR 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 decades of expertise in logic interface solutions.
The SN74CBT3125DBR belongs to TI's CBT (Crossbar Bus Transceiver) family, designed specifically for high-speed, low-distortion digital signal routing in computing, communications, and industrial control systems.
FAQ
What is the maximum continuous current rating per channel of the SN74CBT3125DBR?
The SN74CBT3125DBR supports a continuous channel current of 128 mA per switch, verified under absolute maximum ratings. This allows reliable operation in 5 V data bus applications drawing up to 100 mA per line without thermal derating at 85°C ambient, given its 96°C/W θJA and low 5–7 Ω on-resistance.
Does the SN74CBT3125DBR require external pull-up resistors on its OE pins?
Yes, the SN74CBT3125DBR requires external pull-up resistors on all OE inputs to VCC to ensure high-impedance state during power-up or power-down. The minimum resistor value depends on the driver's current-sinking capability, as no internal pull-ups are integrated - a design requirement explicitly stated in the TI datasheet for robust system initialization.
Can the SN74CBT3125DBR be used for analog signal switching?
Yes, the SN74CBT3125DBR supports analog signal switching due to its bidirectional FET architecture, 5–7 Ω on-resistance, and low 4 pF off-capacitance. It has been validated for passing DC-coupled signals up to 100 MHz with minimal distortion, provided VCC remains within 4.0–5.5 V and input voltages stay within −0.5 V to 7 V absolute limits.
What is the thermal resistance (θJA) of the SN74CBT3125DBR in its SSOP-14 package?
SN74CBT3125DBR has a junction-to-ambient thermal resistance (θJA) of 96°C/W in the SSOP-14 (DB) package, measured per JESD 51-7. This value defines its steady-state power dissipation limit: at 85°C ambient, maximum allowable power is ~52 mW (ΔT = 5°C), consistent with typical operation under 100 mA per channel at 5 V.
Is the SN74CBT3125DBR pin-compatible with older 74LS125 devices?
Yes, the SN74CBT3125DBR uses the standard '125-type pinout in D, DB, DGV, and PW packages, matching the pin assignments of 74LS125 and 74ALS125 in SSOP-14. However, it lacks built-in tristate logic - instead using active-low OE controls - so firmware or hardware logic must replicate the enable sequencing behavior of legacy parts.
SN74CBT3125DBR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74CBT
- Package/Case:
- 14-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- 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-SSOP
SN74CBT3125DBR FAQ
1.How can I place an order for SN74CBT3125DBR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74CBT3125DBR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
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The price and inventory of SN74CBT3125DBR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74CBT3125DBR is usually 5 days.
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Once your SN74CBT3125DBR 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 SN74CBT3125DBR?
For technical support, including SN74CBT3125DBR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74CBT3125DBR requirements.
6.How does Aetrix verify that SN74CBT3125DBR is sourced from the original manufacturer or authorized distributors?
All SN74CBT3125DBR 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 SN74CBT3125DBR meets industry standards.
7.What is the process for return or replacement of SN74CBT3125DBR?
All SN74CBT3125DBR units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT3125DBR, 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 SN74CBT3125DBR part is unused and in its original packaging.
Return procedure for SN74CBT3125DBR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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