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Texas Instruments SN74CBT6845CDBQR
- Part No.:
- SN74CBT6845CDBQR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 20-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
SN74CBT6845CDBQR.pdf
- Description:
- IC BUS SWITCH 8 X 1:1 20SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,500
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Product details
Overview
SN74CBT6845CDBQR from Texas Instruments is an 8-bit bidirectional FET bus switch with near-zero propagation delay (0.15 ns typical at 5 V), 3 Ω typical ON-state resistance, and active undershoot protection up to −2 V on both A and B ports. It supports live insertion in PCI hot-plug systems via B-port precharge to user-selectable BIASV and operates across 4 V to 5.5 V VCC with 0–5 V data I/O signaling.
For engineers reviewing the SN74CBT6845CDBQR datasheet, SN74CBT6845CDBQR pinout, SN74CBT6845CDBQR application, or SN74CBT6845CDBQR equivalent, key selection criteria include its Ioff partial-power-down capability, 5.5 pF typical OFF-state I/O capacitance, TTL/CMOS-compatible control inputs, and SSOP-DBQ package compatibility with legacy board layouts.
Technical Context
The SN74CBT6845CDBQR implements eight independent analog/digital transmission gates controlled by a single OE input, enabling bidirectional signal flow when OE is low and high-impedance isolation when OE is high. Its internal bias circuit precharges B-port terminals to BIASV through a 10-kΩ equivalent resistor during power-down or disable states.
Undershoot protection circuitry actively monitors A/B port voltages and forces the switch into OFF state if −2 V undershoot is detected, preventing false logic transitions. The device meets JESD 78 Class II latch-up immunity (>100 mA) and JESD 22 ESD ratings (2000-V HBM, 1000-V CDM), supporting robust operation in electrically noisy industrial and computing environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4 V to 5.5 V - Enables direct interface with 5-V TTL and mixed-voltage systems without level shifters. |
| ron (Typ) | 3 Ω - Minimizes voltage drop and signal distortion for high-speed digital and analog signals up to ±128 mA per channel. |
| tpd (Typ) | 0.15 ns at 5 V - Near-zero propagation delay preserves timing integrity in high-frequency bus gating applications. |
| Cio(OFF) (Typ) | 5.5 pF - Low OFF-capacitance reduces capacitive loading and crosstalk on shared buses. |
| Ioff (Max) | 10 µA at VCC = 0 V - Ensures true isolation and prevents backflow current during partial power-down sequences. |
| Undershoot Protection | −2 V on A/B ports - Prevents erroneous switching during live card insertion by holding switch OFF during negative transients. |
| BIASV Range | 0 V to VCC - Allows precise precharge voltage tuning to match receiver input thresholds and suppress live-insertion noise. |
| ICC (Max) | 3 µA - Ultra-low quiescent current supports energy-sensitive embedded and portable designs. |
Pinout & Package
SN74CBT6845CDBQR is housed in a 20-pin SSOP (Shrink Small Outline Package) with 0.65 mm pitch, 7.2 mm × 5.3 mm body size, and exposed thermal pad not present - compatible with standard SSOP reflow profiles and automated assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OE | Output Enable control input | Active-low global enable: drives all 8 switches ON (low) or OFF (high); requires pullup to VCC for power-up safety. |
| A1–A8 | Port A data I/O terminals | Bidirectional analog/digital signal path; support 0–5 V signaling and undershoot clamping to −2 V. |
| B1–B8 | Port B data I/O terminals | Bidirectional path with internal precharge to BIASV during OE high or VCC = 0; enables glitch-free hot-plug. |
| BIASV | Bias supply input | User-supplied voltage (0–VCC) setting precharge level for B-port; critical for matching receiver threshold in PCI systems. |
| VCC | Power supply | 4–5.5 V main supply; powers internal logic and switch FETs; must be stable before applying signals. |
| GND | Ground reference | Common return for VCC, BIASV, and all I/O; requires low-impedance PCB connection to minimize noise coupling. |
Key Features
| Feature | Design Value |
|---|---|
| Live-insertion noise suppression | B-port precharge to BIASV minimizes signal glitches during hot-plug by avoiding receiver input threshold crossing. |
| Partial-power-down support | Ioff limits backflow current to ≤10 µA when VCC = 0, enabling safe integration into multi-rail systems with staggered power sequencing. |
| Robust signal integrity | 5.5 pF OFF-state capacitance and 3 Ω ON-resistance preserve edge rates and reduce reflections on high-speed buses. |
| Universal voltage compatibility | 0–5 V data I/O range and TTL/3.3-V/5-V CMOS-compatible control inputs simplify interfacing across mixed-voltage platforms. |
| Fail-safe undershoot handling | Dedicated protection circuitry forces OFF state during −2 V transients, preventing latch-up or false logic assertion on A/B ports. |
Applications
| PCI Hot-Plug Interface | Memory Interleaving Bus Isolation |
|---|---|
Use Scenario: Inserting/removing expansion cards into live PCI backplanes without disrupting system operation. IC Role / Device Role / Timing Role: Bidirectional bus switch isolating card-side signals from host bus while precharging B-port to match host receiver thresholds. Use Value: Eliminates insertion-induced glitches by ensuring B-port voltage remains outside host receiver's input transition region during contact bounce. | Use Scenario: Dynamically routing memory address/data lines between multiple DRAM banks in interleaved architectures. IC Role / Device Role / Timing Role: Low-latency, low-distortion signal gate enabling fast bank switching with sub-nanosecond propagation delay. Use Value: Maintains timing margins under 100 MHz+ memory clocks due to 0.15 ns tpd and 3 Ω ron, reducing setup/hold violations. |
| Low-Distortion Analog Signal Gating | Legacy System Bus Isolation |
Use Scenario: Enabling/disabling audio or sensor analog signals in mixed-signal SoC test fixtures or programmable I/O modules. IC Role / Device Role / Timing Role: Analog-transparent FET switch with flat frequency response up to 100+ MHz and minimal THD from low ron and Cio. Use Value: Preserves signal fidelity for ±2.5 V analog waveforms with <0.01% distortion, verified by 5.5 pF Cio(OFF) and 13.5 pF Cio(ON). | Use Scenario: Isolating legacy ISA or LPC bus segments during firmware updates or diagnostic mode entry. IC Role / Device Role / Timing Role: High-impedance break-before-make switch decoupling bus sections while maintaining voltage rail compatibility. Use Value: Prevents bus contention during reset sequences using Ioff and undershoot protection, ensuring reliable boot from powered-down peripherals. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus switch applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74CBTD6800DBQR | Includes integrated 25-Ω series termination resistors on A/B ports; higher ron (5 Ω typical); supports 3.3-V only VCC (2.3–3.6 V). | Optimized for point-to-point DDR memory traces requiring impedance matching; not suitable for 5-V PCI or mixed-voltage signaling. | Select when trace termination is required and system operates exclusively at 3.3 V; avoid for 5-V hot-plug or analog gating. |
| SN74CB3Q3245PWR | Higher bandwidth (300 MHz), lower Cio(OFF) (3.5 pF), but no BIASV precharge or undershoot protection; requires external bias network for live insertion. | Better for high-frequency serial links (e.g., PCIe Gen1 clock forwarding), but lacks native hot-plug robustness for card-edge interfaces. | Choose for speed-critical digital-only paths where live-insertion noise is mitigated externally; not drop-in for PCI-compliant designs. |
Compared with SN74CBT6845CDBQR, SN74CBTD6800DBQR trades hot-plug readiness for built-in termination, while SN74CB3Q3245PWR sacrifices undershoot immunity and BIASV control for higher bandwidth - making SN74CBT6845CDBQR uniquely suited for standards-compliant PCI hot-plug and mixed-signal bus isolation.
Availability
SN74CBT6845CDBQR is available at Aetrix Electronics and suitable for PCI hot-plug interfaces, memory interleaving subsystems, and low-distortion analog signal gating requiring stable component supply across industrial, computing, and test equipment programs.
Supply support for SN74CBT6845CDBQR 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 high-reliability interface solutions.
The SN74CBT6845CDBQR belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered specifically for zero-delay, low-distortion bus switching in hot-plug-capable computing and communications infrastructure.
FAQ
What is the maximum undershoot voltage the SN74CBT6845CDBQR can withstand on its A and B ports?
The SN74CBT6845CDBQR provides active undershoot protection up to −2 V on both A and B ports, as confirmed in the absolute maximum ratings and functional description. This protection operates by sensing undershoot events and forcing the internal switch into the OFF state to prevent erroneous conduction or logic corruption. The −2 V limit is specified under recommended operating conditions and applies regardless of VCC or BIASV voltage levels.
Does the SN74CBT6845CDBQR support partial-power-down operation, and how is it implemented?
Yes, the SN74CBT6845CDBQR supports partial-power-down operation via its Ioff feature. When VCC = 0 V, the device limits backflow current to ≤10 µA (max) across all I/O pins, preventing damage to powered-down circuitry. This behavior is guaranteed over the full −40°C to 85°C temperature range and is validated per JESD 78 Class II latch-up testing. The Ioff specification ensures safe integration into multi-rail systems with independent power sequencing.
What is the role of the BIASV pin on the SN74CBT6845CDBQR, and what voltage range is allowed?
The BIASV pin on the SN74CBT6845CDBQR sets the precharge voltage for the B-port terminals during OE-high or power-down states, minimizing live-insertion noise. It accepts a user-supplied voltage from 0 V to VCC (i.e., 0–5.5 V), allowing precise alignment with downstream receiver input thresholds. The internal precharge path presents a 10-kΩ equivalent resistance, and BIASV must be stable before OE is asserted high to ensure glitch-free operation during hot-plug events.
Can the SN74CBT6845CDBQR be used for analog signal switching, and what parameters support this use?
Yes, the SN74CBT6845CDBQR is qualified for analog signal switching due to its low ON-state resistance (3 Ω typical), flat frequency response, and low OFF-state capacitance (5.5 pF typical). Its ron variation is minimal across 0–5 V signal swing, and Cio(ON) is 13.5 pF - both values preserve signal integrity for audio, sensor, and test signals up to ~100 MHz. The absence of body diodes in the FET structure and undershoot protection further enhance analog reliability.
What package type and dimensions does the SN74CBT6845CDBQR use, and is it RoHS compliant?
The SN74CBT6845CDBQR uses a 20-pin SSOP (Shrink Small Outline Package) with 0.65 mm lead pitch, 7.2 mm × 5.3 mm body size, and 1.2 mm max height (PW0020A outline). It is RoHS compliant with NiPdAu lead finish and rated MSL Level-1 (260°C, unlimited floor life). The part marking is "CBT6845C", and tape-and-reel packaging supports automated SMT assembly with 2000 units per reel.
SN74CBT6845CDBQR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74CBT
- Package/Case:
- 20-SSOP (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Type:
- Bus Switch
- Circuit:
- 8 x 1:1
- Independent Circuits:
- 1
- 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:
- 20-SSOP
SN74CBT6845CDBQR FAQ
1.How can I place an order for SN74CBT6845CDBQR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74CBT6845CDBQR 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 SN74CBT6845CDBQR reliable?
The price and inventory of SN74CBT6845CDBQR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74CBT6845CDBQR is usually 5 days.
3.What payment methods are accepted for SN74CBT6845CDBQR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74CBT6845CDBQR transactions.
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4.How is shipping managed for SN74CBT6845CDBQR?
SN74CBT6845CDBQR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74CBT6845CDBQR 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 SN74CBT6845CDBQR?
For technical support, including SN74CBT6845CDBQR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74CBT6845CDBQR requirements.
6.How does Aetrix verify that SN74CBT6845CDBQR is sourced from the original manufacturer or authorized distributors?
All SN74CBT6845CDBQR 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 SN74CBT6845CDBQR meets industry standards.
7.What is the process for return or replacement of SN74CBT6845CDBQR?
All SN74CBT6845CDBQR units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT6845CDBQR, 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 SN74CBT6845CDBQR part is unused and in its original packaging.
Return procedure for SN74CBT6845CDBQR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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