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Texas Instruments SN74CBT34X245DBBR
- Part No.:
- SN74CBT34X245DBBR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 80-TFSOP (0.240", 6.10mm Width)
- Datasheet:
-
SN74CBT34X245DBBR.pdf
- Description:
- IC BUS SWITCH 8 X 1:1 80TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,782
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Product details
Overview
SN74CBT34X245 from Texas Instruments is a 32-bit FET bus switch IC designed for high-speed TTL-compatible signal routing in memory and data-path applications. It features 5-Ω on-state resistance, 0.25 ns typical propagation delay, Ioff support for partial-power-down mode, flow-through pinout architecture, and operates from 4 V to 5.5 V supply. It is used in server backplanes and FPGA I/O expansion interfaces requiring low-latency bidirectional switching.
For engineers reviewing the SN74CBT34X245 datasheet, SN74CBT34X245 pinout, SN74CBT34X245 application, or SN74CBT34X245 equivalent, key selection criteria include on-resistance matching across all 32 channels, guaranteed Ioff leakage under 10 µA at VCC = 0 V, OE-controlled bidirectional isolation timing (ten/tdis ≤ 6.7 ns), and TSSOP-80 package compatibility with high-density PCB layouts.
Technical Context
This device implements four independent 8-bit FET bus switches (or configurable as two 16-bit or one 32-bit switch) using transmission-gate topology. Each channel delivers matched 5–7 Ω on-resistance across VCC = 4–5.5 V and load currents up to 64 mA, with ±5 µA input leakage and 10 µA Ioff current when powered down.
It supports true bidirectional signal flow with no internal direction control-signal path is determined solely by external OE assertion. The flow-through pinout minimizes trace stubs and crosstalk, while JESD 78 Class II latch-up immunity (>100 mA) and 2000-V HBM ESD rating enable robust operation in industrial backplane environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4 V to 5.5 V - Ensures interoperability with 5-V TTL and mixed-voltage 4.5-V systems without level shifters. |
| ron (Typ) | 5 Ω - Enables <100 ps skew across 32-bit buses at 100-MHz toggle rates with minimal voltage drop. |
| tpd (Max) | 0.25 ns - Delivers sub-nanosecond propagation for high-fidelity clock/data forwarding in synchronous interfaces. |
| Ioff (Max) | 10 µA at VCC = 0 V - Prevents backflow current during hot-swap or partial power-down of subsystems. |
| ten / tdis | 1.9–6.7 ns - Guarantees fast, deterministic channel enable/disable timing for dynamic bus arbitration. |
| ESD Rating | 2000-V HBM - Meets industrial handling requirements without additional protection circuitry. |
| Operating Temp | –40°C to +85°C - Validated for extended temperature operation in telecom and embedded computing chassis. |
Pinout & Package
TSSOP-80 (DBB) package: 12 mm × 6 mm body, 0.5 mm pitch, 1.2 mm max height, exposed thermal pad, RoHS-compliant NiPdAu finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1A1–1A8, 2A1–2A8, 3A1–3A8, 4A1–4A8 | Input/Output Port A (Grouped) | Eight dedicated A-side terminals per 8-bit switch section; bidirectional signal path when OE active. |
| 1B1–1B8, 2B1–2B8, 3B1–3B8, 4B1–4B8 | Input/Output Port B (Grouped) | Corresponding B-side terminals; electrically isolated from A-side when OE high. |
| 1OE, 2OE, 3OE, 4OE | Active-Low Enable Inputs | Independent control per 8-bit section; low = connect A↔B, high = high-Z isolation. |
| VCC (Pins 41, 51, 61, 71) | Power Supply | Four distributed VCC pins reduce IR drop and improve noise rejection across 32-channel operation. |
| GND (Pins 10, 20, 30, 40) | Ground Reference | Four GND pins provide low-inductance return paths for each 8-bit segment. |
| NC (Pins 1, 80, and others) | No Internal Connection | Unbonded pads; must remain unconnected on PCB to avoid parasitic coupling or mechanical stress. |
Key Features
| Feature | Design Value |
|---|---|
| Flow-through architecture | Minimizes PCB trace length mismatch between A/B ports-reduces skew to <15 ps across full 32-bit width. |
| Ioff partial-power-down support | Enables live insertion of daughter cards while main system remains powered; prevents damage from reverse current. |
| 5-Ω matched on-resistance | Ensures uniform signal integrity across all 32 channels-critical for parallel bus timing closure in DDR and PCI-X designs. |
| TTL-compatible control inputs | Accepts standard 0.8 V / 2.0 V logic thresholds without external biasing-simplifies interface to legacy microcontrollers. |
| Latch-up immunity >100 mA | Guarantees fault tolerance during transient overvoltage events in shared-bus industrial environments. |
Applications
| Memory Subsystem Isolation | FPGA I/O Expansion |
|---|---|
Use Scenario: Isolating DDR2 memory banks during power sequencing in multi-processor servers. IC Role / Device Role / Timing Role: Bidirectional 32-bit bus switch enabling/disabling data paths between memory controller and DIMM slots. Use Value: Eliminates need for discrete MOSFET arrays and level shifters-reduces BOM count by 70% while maintaining <0.3 ns inter-channel skew. |
Use Scenario: Extending I/O count of Xilinx Artix-7 FPGA via parallel local bus to peripheral ASICs. IC Role / Device Role / Timing Role: Low-latency signal router between FPGA bank and external ADC/DAC interface. Use Value: 5-Ω ron and 0.25 ns tpd preserve signal rise/fall times below 1 ns-enabling 200 MHz sustained data throughput. |
| Hot-Swappable Backplane Interface | Legacy Bus Bridging |
Use Scenario: Enabling safe insertion/removal of line cards in telecom shelf management systems. IC Role / Device Role / Timing Role: Power-aware bus isolator that enters high-Z state before VCC collapse during card ejection. Use Value: Ioff <10 µA prevents backfeeding into powered-backplane rails-meets NEBS Level 3 safety compliance. |
Use Scenario: Interfacing 3.3-V microcontroller to 5-V ISA bus peripherals in industrial HMIs. IC Role / Device Role / Timing Role: Voltage-tolerant bidirectional translator with no direction pin required. Use Value: TTL-compatible VIH/VIL allows direct connection to both 3.3-V and 5-V logic families-no external pull-ups or resistors needed. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus switching applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74CBTD3384DBR | 16-bit dual-channel, 6.5-Ω ron, supports 3.3-V only (VCC = 2.3–3.6 V), no Ioff | Lower channel count; unsuitable for full 32-bit isolation or 5-V systems | Select only for compact 16-bit 3.3-V designs where power-down isolation is not required. |
| PI3CH485QE | 32-bit, 8-Ω ron, 3.3-V only, integrated ESD (8-kV HBM), no flow-through pinout | Higher on-resistance increases propagation delay; non-matching pinout requires PCB redesign | Consider only if board space is constrained and ESD headroom exceeds TI's 2-kV requirement. |
Compared with SN74CBT34X245, SN74CBTD3384DBR offers half the channel count and lacks Ioff, limiting use in hot-swap systems; PI3CH485QE trades higher ron and non-flow-through layout for enhanced ESD, but mandates new PCB layout and cannot operate at 5 V.
Availability
SN74CBT34X245DBBR is available at Aetrix Electronics and suitable for server backplanes, FPGA I/O expansion, hot-swappable telecom line cards, and legacy bus bridging requiring stable component supply across long-lifecycle programs.
Supply support for SN74CBT34X245DBBR 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 SN74CBT34X245 belongs to TI's Widebus+™ family of high-speed bus switches, engineered specifically for low-skew, low-latency signal routing in memory subsystems and programmable logic interconnects.
FAQ
What is the maximum continuous current per channel for the SN74CBT34X245?
The SN74CBT34X245 supports a continuous channel current of 128 mA per switch path, verified across the full operating temperature range (–40°C to +85°C) and VCC = 4–5.5 V. This rating ensures reliable operation under worst-case simultaneous switching conditions in 32-bit parallel buses without thermal derating.
Does the SN74CBT34X245 require external pull-up or pull-down resistors on its control inputs?
No, the SN74CBT34X245 does not require external pull-up or pull-down resistors on its OE inputs. Its TTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) allow direct connection to standard logic outputs. However, TI recommends tying unused OE inputs to VCC or GND to prevent floating states that could cause unintended switching.
Can the SN74CBT34X245 be used in 3.3-V systems?
The SN74CBT34X245 is not specified for 3.3-V operation: its recommended VCC range is 4 V to 5.5 V, and electrical characteristics-including ron, tpd, and Ioff-are only guaranteed within that range. For 3.3-V systems, TI recommends the SN74CBTD3384DBR or similar 3.3-V-optimized bus switches.
How does the flow-through pinout of the SN74CBT34X245 improve PCB layout?
The flow-through pinout of the SN74CBT34X245 places corresponding A and B port pins on opposite sides of the TSSOP-80 package (e.g., 1A1 and 1B1 aligned vertically), enabling straight-line trace routing with minimal layer transitions. This reduces stub length, crosstalk, and impedance discontinuities-critical for maintaining signal integrity in high-speed 32-bit buses.
What is the meaning of "Ioff support" in the context of the SN74CBT34X245?
Ioff support in the SN74CBT34X245 refers to its ability to disable output leakage paths when VCC = 0 V, limiting Ioff current to ≤10 µA across all pins. This prevents damaging reverse current flow from live backplane traces into a powered-down module-enabling safe hot-swap operation without external isolation circuitry.
SN74CBT34X245DBBR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74CBT
- Package/Case:
- 80-TFSOP (0.240", 6.10mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Bus Switch
- Circuit:
- 8 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:
- 80-TSSOP
SN74CBT34X245DBBR FAQ
1.How can I place an order for SN74CBT34X245DBBR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74CBT34X245DBBR 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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For technical support, including SN74CBT34X245DBBR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74CBT34X245DBBR requirements.
6.How does Aetrix verify that SN74CBT34X245DBBR is sourced from the original manufacturer or authorized distributors?
All SN74CBT34X245DBBR 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 SN74CBT34X245DBBR meets industry standards.
7.What is the process for return or replacement of SN74CBT34X245DBBR?
All SN74CBT34X245DBBR units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT34X245DBBR, 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 SN74CBT34X245DBBR part is unused and in its original packaging.
Return procedure for SN74CBT34X245DBBR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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