SN74CBT6845CDWR

Overview

The SN74CBT6845CDWR is an 8-bit TTL-compatible FET bus switch manufactured by Texas Instruments. It operates within a VCC range of 4 V to 5.5 V and supports bidirectional data flow with near-zero propagation delay. The device features low ON-state resistance (ron) characteristics, typically 3 Ω at VCC = 4.5 V, and low input/output capacitance (Cio(OFF) = 5.5 pF typical). It includes active undershoot protection on A and B ports up to -2 V and precharges the B port via a bias voltage (BIASV) to minimize live-insertion noise. The component is housed in a DW (SOIC-20) package.

Feature Summary

• Active undershoot-protection circuitry on A and B ports ensures proper OFF state during undershoot events up to -2 V.
• B-port outputs are precharged by a user-selectable bias voltage (BIASV) to minimize signal distortion during live insertion and hot-plugging.
• Supports partial-power-down mode operation using Ioff feature to prevent damaging backflow current when powered down.
• Data and control inputs provide undershoot clamp diodes for enhanced signal integrity.

Applications

• PCI interface applications
• Memory interleaving systems
• Bus isolation circuits
• Low-distortion signal gating

Procurement Notes

Verify the ordering suffix 'DW' corresponds to the SOIC-20 tube packaging configuration. Confirm that the specific part number matches the required operating temperature range of -40°C to +85°C. Ensure compatibility with the 4 V to 5.5 V supply voltage requirements before procurement.

Selection Notes

Select this component for high-speed digital and analog applications requiring minimal propagation delay and low loading effects. The single output-enable (OE) input simplifies control logic. Consider the BIASV pin functionality if live-insertion noise reduction is critical for the target system design.

Part Context

This device belongs to the SN74CBT6845C family of high-speed bus switches. It is designed to replace mechanical relays or discrete transistor switches in applications demanding faster switching speeds and lower power consumption. The family offers various package options including TSSOP, SSOP, and VQFN.

Replacement Considerations

SN74CBT6845CDW (Tube version)

FAQ

How does the device handle live insertion?

The B port is precharged to a user-selectable bias voltage (BIASV) through an equivalent 10-kΩ resistor when OE is high, minimizing glitching effects caused by parasitic capacitance during card insertion.

What is the function of the Ioff feature?

The Ioff feature ensures that damaging current will not backflow through the device when it is powered down (VCC = 0 V), providing isolation during partial-power-down applications.