SN74CBT6845CDBQR

Overview

The SN74CBT6845CDBQR is an octal FET bus switch manufactured by Texas Instruments, housed in a 20-pin QSOP package. It operates within a supply voltage range of 4 V to 5.5 V and supports bidirectional data flow with near-zero propagation delay. The device features 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. Key electrical parameters include a maximum ON-state resistance of 12 Ω at VCC = 4 V, a typical input/output capacitance of 5.5 pF when off, and a maximum supply current of 3 µA.

Feature Summary

• Active undershoot protection circuitry ensures proper OFF state during signal events down to -2 V
• B-port outputs are precharged to a user-selectable bias voltage to minimize signal distortion during hot-plugging
• Supports partial-power-down mode operation through Ioff isolation to prevent backflow current
• Low input/output capacitance minimizes loading effects and signal distortion

Applications

• PCI interface applications supporting hot-plug operations
• Memory interleaving systems requiring low-distortion signal gating
• Bus isolation circuits for digital and analog signal routing

Procurement Notes

Verify that the ordering suffix DBQR corresponds specifically to the SSOP (QSOP) tape-and-reel packaging configuration. Confirm the component meets RoHS compliance standards and matches the specified operating temperature range of -40°C to +85°C. Ensure the datasheet revision aligns with the required design specifications before finalizing procurement orders.

Selection Notes

Select this component when designing systems requiring high-speed bidirectional switching with minimal signal degradation. The integrated BIASV pin allows customization of precharge levels to match specific receiver threshold voltages. Verify that control inputs can be driven by TTL or 5-V/3.3-V CMOS outputs to ensure compatibility with existing logic families.

Part Context

This part belongs to the SN74CBT6845C family of high-speed TTL-compatible FET bus switches. It shares functional characteristics with other variants in the series but differs in physical packaging and reel orientation. The device is designed to replace older discrete switching solutions by integrating protection and precharge features into a single compact IC.

Replacement Considerations

Direct substitutes include SN74CBT6845CDW, SN74CBT6845CPW, and SN74CBT6845CRGYR. These alternatives offer identical electrical performance but utilize different packages such as SOIC, TSSOP, or VQFN. Verify pinout compatibility and thermal requirements when transitioning between package types.