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SN74CBT6845C

ACTIVE

5-V, 1:1 (SPST), 8-channel FET bus switch with precharged outputs & –2-V undershoot protection

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Data sheet

SN74CBT6845C

ACTIVE
Data sheet Order now

Product details

Configuration 1:1 SPST Number of channels 8 Power supply voltage - single (V) 5 Protocols Analog Ron (typ) (Ω) 3 CON (typ) (pF) 13.5 Bandwidth (MHz) 200 Operating temperature range (°C) -40 to 85 Features Undershoot protection Input/output continuous current (max) (mA) 128 Rating Catalog Drain supply voltage (max) (V) 5.5 Supply voltage (max) (V) 5.5
Configuration 1:1 SPST Number of channels 8 Power supply voltage - single (V) 5 Protocols Analog Ron (typ) (Ω) 3 CON (typ) (pF) 13.5 Bandwidth (MHz) 200 Operating temperature range (°C) -40 to 85 Features Undershoot protection Input/output continuous current (max) (mA) 128 Rating Catalog Drain supply voltage (max) (V) 5.5 Supply voltage (max) (V) 5.5
TSSOP (PW) 20 41.6 mm² 6.5 x 6.4 VQFN (RGY) 20 15.75 mm² 4.5 x 3.5
  • Undershoot Protection for Off-Isolation on A and B Ports Up To –2 V
  • B-Port Outputs Are Precharged by Bias Voltage (BIASV) to Minimize Signal Distortion During Live Insertion and Hot-Plugging
  • Supports PCI Hot Plug
  • Bidirectional Data Flow, With Near-Zero Propagation Delay
  • Low ON-State Resistance (ron) Characteristics (ron = 3 Typical)
  • Low Input/Output Capacitance Minimizes Loading and Signal Distortion (Cio(OFF) = 5.5 pF Typical)
  • Data and Control Inputs Provide Undershoot Clamp Diodes
  • Low Power Consumption (ICC = 3 µA Max)
  • VCC Operating Range From 4 V to 5.5 V
  • Data I/Os Support 0 to 5-V Signaling Levels (0.8-V, 1.2-V, 1.5-V, 1.8-V, 2.5-V, 3.3-V, 5-V)
  • Control Inputs Can be Driven by TTL or 5-V/3.3-V CMOS Outputs
  • Ioff Supports Partial-Power-Down Mode Operation
  • Latch-Up Performance Exceeds 100 mA Per JESD 78, Class II
  • ESD Performance Tested Per JESD 22
    • 2000-V Human-Body Model (A114-B, Class II)
    • 1000-V Charged-Device Model (C101)
  • Supports Both Digital and Analog Applications: PCI Interface, Memory Interleaving, Bus Isolation, Low-Distortion Signal Gating
  • Undershoot Protection for Off-Isolation on A and B Ports Up To –2 V
  • B-Port Outputs Are Precharged by Bias Voltage (BIASV) to Minimize Signal Distortion During Live Insertion and Hot-Plugging
  • Supports PCI Hot Plug
  • Bidirectional Data Flow, With Near-Zero Propagation Delay
  • Low ON-State Resistance (ron) Characteristics (ron = 3 Typical)
  • Low Input/Output Capacitance Minimizes Loading and Signal Distortion (Cio(OFF) = 5.5 pF Typical)
  • Data and Control Inputs Provide Undershoot Clamp Diodes
  • Low Power Consumption (ICC = 3 µA Max)
  • VCC Operating Range From 4 V to 5.5 V
  • Data I/Os Support 0 to 5-V Signaling Levels (0.8-V, 1.2-V, 1.5-V, 1.8-V, 2.5-V, 3.3-V, 5-V)
  • Control Inputs Can be Driven by TTL or 5-V/3.3-V CMOS Outputs
  • Ioff Supports Partial-Power-Down Mode Operation
  • Latch-Up Performance Exceeds 100 mA Per JESD 78, Class II
  • ESD Performance Tested Per JESD 22
    • 2000-V Human-Body Model (A114-B, Class II)
    • 1000-V Charged-Device Model (C101)
  • Supports Both Digital and Analog Applications: PCI Interface, Memory Interleaving, Bus Isolation, Low-Distortion Signal Gating

The SN74CBT6845C is a high-speed TTL-compatible FET bus switch with low ON-state resistance (ron), allowing for minimal propagation delay. Active Undershoot-Protection Circuitry on the A and B ports of the SN74CBT6845C provides protection for undershoot up to –2 V by sensing an undershoot event and ensuring that the switch remains in the proper OFF state. The device also precharges the B port to a user-selectable bias voltage (BIASV) to minimize live-insertion noise.

The SN74CBT6845C is an 8-bit bus switch with a single output-enable (OE\) input. When OE\ is low, the 8-bit bus switch is ON, and the A port is connected to the B port, allowing bidirectional data flow between ports. When OE\ is high, the 8-bit bus switch is OFF, and a high-impedance state exists between the A and B ports. The B port is precharged to BIASV through the equivalent of a 10-k resistor when OE\ is high, or if the device is powered down (VCC = 0 V).

During insertion (or removal) of a card into (or from) an active bus, the card’s output voltage may be close to GND. When the connector pins make contact, the card’s parasitic capacitance tries to force the bus signal to GND, creating a possible glitch on the active bus. This glitching effect can be reduced by using a bus switch with precharged bias voltage (BIASV) of the bus switch equal to the input threshold voltage level of the receivers on the active bus. This method will ensure that any glitch produced by insertion (or removal) of the card will not cross the input threshold region of the receivers on the active bus, minimizing the effects of live-insertion noise.

This device is fully specified for partial-power-down applications using Ioff. The Ioff feature ensures that damaging current will not backflow through the device when it is powered down. The device has isolation during power off.

To ensure the high-impedance state during power up or power down, OE\ should be tied to VCC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

The SN74CBT6845C is a high-speed TTL-compatible FET bus switch with low ON-state resistance (ron), allowing for minimal propagation delay. Active Undershoot-Protection Circuitry on the A and B ports of the SN74CBT6845C provides protection for undershoot up to –2 V by sensing an undershoot event and ensuring that the switch remains in the proper OFF state. The device also precharges the B port to a user-selectable bias voltage (BIASV) to minimize live-insertion noise.

The SN74CBT6845C is an 8-bit bus switch with a single output-enable (OE\) input. When OE\ is low, the 8-bit bus switch is ON, and the A port is connected to the B port, allowing bidirectional data flow between ports. When OE\ is high, the 8-bit bus switch is OFF, and a high-impedance state exists between the A and B ports. The B port is precharged to BIASV through the equivalent of a 10-k resistor when OE\ is high, or if the device is powered down (VCC = 0 V).

During insertion (or removal) of a card into (or from) an active bus, the card’s output voltage may be close to GND. When the connector pins make contact, the card’s parasitic capacitance tries to force the bus signal to GND, creating a possible glitch on the active bus. This glitching effect can be reduced by using a bus switch with precharged bias voltage (BIASV) of the bus switch equal to the input threshold voltage level of the receivers on the active bus. This method will ensure that any glitch produced by insertion (or removal) of the card will not cross the input threshold region of the receivers on the active bus, minimizing the effects of live-insertion noise.

This device is fully specified for partial-power-down applications using Ioff. The Ioff feature ensures that damaging current will not backflow through the device when it is powered down. The device has isolation during power off.

To ensure the high-impedance state during power up or power down, OE\ should be tied to VCC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.
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Technical documentation

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Type Title Date
* Data sheet SN74CBT6845C datasheet 06 Oct 2003
Application note Selecting the Correct Texas Instruments Signal Switch (Rev. E) PDF | HTML 02 Jun 2022
Application note Multiplexers and Signal Switches Glossary (Rev. B) PDF | HTML 01 Dec 2021
Application note CBT-C, CB3T, and CB3Q Signal-Switch Families (Rev. C) PDF | HTML 19 Nov 2021
Application brief Eliminate Power Sequencing with Powered-off Protection Signal Switches (Rev. C) PDF | HTML 06 Jan 2021
Selection guide Little Logic Guide 2018 (Rev. G) 06 Jul 2018
Selection guide Logic Guide (Rev. AB) 12 Jun 2017
Application note Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) 02 Dec 2015
User guide LOGIC Pocket Data Book (Rev. B) 16 Jan 2007
More literature Digital Bus Switch Selection Guide (Rev. A) 10 Nov 2004
Application note Semiconductor Packing Material Electrostatic Discharge (ESD) Protection 08 Jul 2004
User guide Signal Switch Data Book (Rev. A) 14 Nov 2003
Application note Bus FET Switch Solutions for Live Insertion Applications 07 Feb 2003

Design & development

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Interface adapter

LEADED-ADAPTER1 — Surface mount to DIP header adapter for quick testing of TI's 5, 8, 10, 16 & 24-pin leaded packages

The EVM-LEADED1 board allows for quick testing and bread boarding of TI's common leaded packages.  The board has footprints to convert TI's D, DBQ, DCT,DCU, DDF, DGS, DGV, and PW surface mount packages to 100mil DIP headers.     

User guide: PDF
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Simulation model

SN74CBT6845C IBIS Model

SCDM051.ZIP (27 KB) - IBIS Model
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Package Pins CAD symbols, footprints & 3D models
TSSOP (PW) 20 Ultra Librarian
VQFN (RGY) 20 Ultra Librarian
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