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Home > Products > Integrated Circuits (ICs) > Logic > Signal Switches, Multiplexers, Decoders

Texas Instruments SN74CBT3125CD

Name: SN74CBT3125CD
Brand: Texas Instruments
SKU: SN74CBT3125CD
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74CBT3125CD

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

Package:: 14-SOIC (0.154", 3.90mm Width)

Datasheet:: SN74CBT3125CD.pdf

Description:: IC BUS SWITCH 1 X 1:1 14SOIC

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Product details

Overview

SN74CBT3125CD from Texas Instruments is a quad 1-bit FET bus switch IC used for bidirectional signal gating in high-speed digital systems. It features near-zero propagation delay (0.15 ns typical at 5 V), low ON-state resistance (3 Ω typical), and supports 0–5-V signaling across TTL/CMOS logic families - deployed in USB interface isolation and low-distortion data path switching.

For engineers reviewing the SN74CBT3125CD datasheet, SN74CBT3125CD pinout, SN74CBT3125CD application, or SN74CBT3125CD equivalent, key selection criteria include undershoot protection to −2 V, I_off-enabled partial-power-down operation, and SOIC-14 package compatibility with legacy board layouts requiring minimal trace routing changes.

Technical Context

This device implements four independent single-pole single-throw (SPST) analog switches using NMOS pass transistors with integrated undershoot-protection circuitry on both A and B ports. Each switch is controlled by a dedicated active-low output-enable input (1OE–4OE), enabling per-channel isolation without affecting other paths.

It operates within a 4–5.5 V supply range, supports mixed-voltage I/O (0–5.5 V), and delivers rail-to-rail analog/digital signal transmission with 5 pF typical OFF-state capacitance and ±128 mA maximum ON-state current - making it suitable for hot-swap-capable bus architectures and level-translating interconnects.

Key Specifications

Parameter	Value and Actual Design Meaning
VCC Range	4 V to 5.5 V - ensures compatibility with 5-V TTL and 3.3-V CMOS systems via level-agnostic control inputs.
ron (Typ)	3 Ω - minimizes voltage drop and timing skew in high-speed data lines up to 100+ MHz.
tpd (Typ)	0.15 ns at VCC = 5 V - enables sub-nanosecond signal gating critical for USB 1.1/2.0 and parallel bus isolation.
Cio(OFF)	5 pF typical - reduces capacitive loading and signal distortion on shared buses during OFF-state isolation.
Ioff	10 µA max at VCC = 0 V - prevents backflow current and ensures safe isolation during system power sequencing.
Undershoot Protection	−2 V on A/B ports - protects downstream logic from negative transients during hot-plug or cable disconnect events.
ESD Rating	2000-V HBM, 1000-V CDM - meets industrial-grade robustness requirements without external protection diodes.

Pinout & Package

SN74CBT3125CD is housed in a 14-pin SOIC (D) package with 1.27 mm pitch, 8.75 mm × 3.91 mm body size, and 1.75 mm max height - compatible with standard SOIC footprints and reflow profiles (MSL Level-1).

Pin/Terminal	Circuit Role	Design Meaning
1OE, 2OE, 3OE, 4OE	Active-low channel enable	Individually controls ON/OFF state of each 1-bit switch; pulled high via resistor for power-up high-impedance safety.
1A–4A, 1B–4B	Bidirectional signal terminals	Passes signals in either direction when enabled; supports 0–5-V logic levels and analog waveforms below 5.5 V.
VCC	Power supply	Supplies internal bias and switch driver circuitry; must be stable within 4–5.5 V for guaranteed ron and timing specs.
GND	Ground reference	Common return path for all channels and control logic; requires low-impedance PCB connection to minimize noise coupling.
NC (Pins 1 & 14)	No internal connection	Unbonded pins; must remain unconnected on PCB to avoid parasitic coupling or mechanical stress.

Key Features

Feature	Design Value
Undershoot protection	Clamps A/B port voltages to −2 V during negative transients, preventing latch-up and ensuring reliable OFF-state isolation.
Ioff partial-power-down	Blocks reverse current flow when VCC = 0 V, enabling live insertion/removal in multi-rail systems without damaging adjacent circuitry.
Low capacitance switching	5 pF OFF-state I/O capacitance minimizes bus loading and preserves signal integrity in high-frequency parallel interfaces.
TTL/CMOS-compatible control	Accepts 0.8-V VIL and 2-V VIH thresholds - directly driven by legacy 5-V TTL or modern 3.3-V CMOS outputs without level shifters.
Bidirectional zero-delay path	Enables transparent signal flow in either direction with no added propagation delay beyond intrinsic RC time constant.

Applications

USB 1.1/2.0 Interface Isolation	PCI/ISA Bus Signal Gating
Use Scenario: Isolating upstream/downstream data lines during USB device enumeration or suspend/resume transitions. IC Role / Device Role / Timing Role: Bidirectional signal gate placed between host controller and peripheral PHY to block leakage and prevent bus contention. Use Value: Eliminates need for external series resistors or Schottky clamps while maintaining <100 ps timing margin for full-speed USB timing budgets.	Use Scenario: Enabling/disabling legacy expansion card access to shared address/data buses without disrupting active peripherals. IC Role / Device Role / Timing Role: Per-lane switch controlling individual D0–D7 or A0–A19 lines under software-configurable OE control. Use Value: Reduces bus capacitance by 80% vs. traditional buffer-based gating, preserving setup/hold margins at 33 MHz PCI clock rates.
Hot-Swap Backplane Interconnect	Multi-Voltage Logic Translation
Use Scenario: Safely inserting/removing daughter cards into powered backplanes where ground-first mating is not guaranteed. IC Role / Device Role / Timing Role: Front-end isolation switch on each signal line, activated only after power and reference stabilization. Use Value: −2 V undershoot clamping prevents damage to ASIC I/O cells during connector arcing or mis-mating events.	Use Scenario: Interfacing 1.8-V FPGA I/O banks with 3.3-V microcontroller peripherals in mixed-supply SoM designs. IC Role / Device Role / Timing Role: Voltage-agnostic pass gate enabling bidirectional data exchange without direction control or level-shifter latency. Use Value: Supports 0–5-V signaling range with <3 Ω ron, delivering <0.5% voltage drop at 20 mA - sufficient for GPIO, I²C, and SPI level translation.

USB 1.1/2.0 Interface Isolation

PCI/ISA Bus Signal Gating

Use Scenario: Isolating upstream/downstream data lines during USB device enumeration or suspend/resume transitions.

IC Role / Device Role / Timing Role: Bidirectional signal gate placed between host controller and peripheral PHY to block leakage and prevent bus contention.

Use Value: Eliminates need for external series resistors or Schottky clamps while maintaining <100 ps timing margin for full-speed USB timing budgets.

Use Scenario: Enabling/disabling legacy expansion card access to shared address/data buses without disrupting active peripherals.

IC Role / Device Role / Timing Role: Per-lane switch controlling individual D0–D7 or A0–A19 lines under software-configurable OE control.

Use Value: Reduces bus capacitance by 80% vs. traditional buffer-based gating, preserving setup/hold margins at 33 MHz PCI clock rates.

Hot-Swap Backplane Interconnect

Multi-Voltage Logic Translation

Use Scenario: Safely inserting/removing daughter cards into powered backplanes where ground-first mating is not guaranteed.

IC Role / Device Role / Timing Role: Front-end isolation switch on each signal line, activated only after power and reference stabilization.

Use Value: −2 V undershoot clamping prevents damage to ASIC I/O cells during connector arcing or mis-mating events.

Use Scenario: Interfacing 1.8-V FPGA I/O banks with 3.3-V microcontroller peripherals in mixed-supply SoM designs.

IC Role / Device Role / Timing Role: Voltage-agnostic pass gate enabling bidirectional data exchange without direction control or level-shifter latency.

Use Value: Supports 0–5-V signaling range with <3 Ω ron, delivering <0.5% voltage drop at 20 mA - sufficient for GPIO, I²C, and SPI level translation.

Equivalent & Alternatives

The following parts are listed as comparable options for similar bus switch applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74CBTD3384CD	8-bit configuration with higher ron (5 Ω typical) and 10 pF Cio(OFF); includes VCC isolation but no undershoot protection.	Designed for wider data buses (e.g., memory address latching); lacks −2 V port clamping required for USB hot-plug compliance.	Select when consolidating multiple SN74CBT3125CD functions into one 8-bit unit and undershoot events are mitigated externally.
74LVC1G3157GW	Single SPDT switch in SC-70; ron = 6 Ω typical, Cio(OFF) = 4.5 pF, no undershoot protection, VCC = 1.65–5.5 V.	Targeted at space-constrained point-of-load switching (e.g., sensor multiplexing); lacks multi-channel enable architecture and Ioff support.	Choose for ultra-low-pin-count, low-density signal routing where per-channel OE control and power-down safety are not required.

Compared with SN74CBT3125CD, SN74CBTD3384CD trades undershoot immunity for higher channel density, while 74LVC1G3157GW sacrifices architectural flexibility and system-level safety for footprint reduction - making SN74CBT3125CD optimal for robust, multi-channel, hot-plug-ready isolation.

Availability

SN74CBT3125CD is available at Aetrix Electronics and suitable for USB interface isolation, PCI bus gating, and hot-swap backplane interconnects requiring stable component supply, long-term lifecycle support, and RoHS-compliant SOIC packaging.

Supply support for SN74CBT3125CD 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 solutions with over 50 years of innovation in high-reliability interface ICs.

The SN74CBT3125CD belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered for low-latency, low-distortion signal routing in mixed-voltage digital systems - particularly targeting legacy bus architectures and USB-compliant peripheral isolation.

FAQ

What is the maximum signal frequency supported by SN74CBT3125CD?

SN74CBT3125CD does not specify a hard frequency limit but supports signal integrity up to ≥100 MHz due to its 5 pF OFF-state capacitance, 3 Ω ON-resistance, and 0.15 ns propagation delay. Real-world performance depends on PCB layout, load capacitance, and drive strength - verified in USB 2.0 full-speed (12 Mbps) and PCI 33 MHz applications using SN74CBT3125CD.

Can SN74CBT3125CD operate with a 3.3-V supply?

No - SN74CBT3125CD requires VCC between 4 V and 5.5 V per its recommended operating conditions. While data I/Os tolerate 0–5.5 V, the internal switch biasing and control logic are not functional below 4 V. For 3.3-V systems, consider SN74LVC1G3157 or SN74AUC1G66 as alternatives.

How does the Ioff feature protect circuits during power-down?

The Ioff feature disables internal conduction paths when VCC = 0 V, limiting leakage current to ≤10 µA even with up to 5.5 V applied to A/B ports. This prevents back-driving powered-down sections of a system - a critical safeguard in multi-rail designs where SN74CBT3125CD isolates active and dormant subsystems.

Is SN74CBT3125CD pin-compatible with other CBT-series switches?

SN74CBT3125CD shares the same SOIC-14 pinout with SN74CBT3244CD and SN74CBT3245CD, but differs in channel count and enable logic polarity. Its 1OE–4OE inputs are active-low, whereas SN74CBT3244CD uses active-high enables. Direct substitution requires schematic review of OE signal polarity and channel mapping.

Does SN74CBT3125CD require external pull-up resistors on OE pins?

Yes - to ensure high-impedance state during power-up/power-down, each OE pin should be tied to VCC through a pull-up resistor. TI recommends ≥10 kΩ for standard CMOS drivers; lower values (e.g., 4.7 kΩ) improve noise immunity but increase static current. This requirement applies to every SN74CBT3125CD instance in the design.

SN74CBT3125CD Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74CBT

Package/Case:: 14-SOIC (0.154", 3.90mm Width)

Packaging:: Bulk

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-SOIC

SN74CBT3125CD FAQ

1.How can I place an order for SN74CBT3125CD through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74CBT3125CD 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 SN74CBT3125CD reliable?

The price and inventory of SN74CBT3125CD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74CBT3125CD is usually 5 days.

3.What payment methods are accepted for SN74CBT3125CD?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74CBT3125CD transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74CBT3125CD?

SN74CBT3125CD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74CBT3125CD 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 SN74CBT3125CD?

For technical support, including SN74CBT3125CD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74CBT3125CD requirements.

6.How does Aetrix verify that SN74CBT3125CD is sourced from the original manufacturer or authorized distributors?

All SN74CBT3125CD 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 SN74CBT3125CD meets industry standards.

7.What is the process for return or replacement of SN74CBT3125CD?

All SN74CBT3125CD units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT3125CD, 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 SN74CBT3125CD part is unused and in its original packaging.

Return procedure for SN74CBT3125CD:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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