Texas Instruments SN74CBT6845CPWR

Overview

SN74CBT6845CPWR from Texas Instruments is an 8-bit TTL-compatible FET bus switch with bidirectional data flow, near-zero propagation delay (0.15 ns typical at 5 V), 3 Ω typical ON-state resistance, and undershoot protection up to −2 V on both A and B ports - deployed in PCI hot-plug interfaces and memory interleaving systems.

For engineers reviewing the SN74CBT6845CPWR datasheet, SN74CBT6845CPWR pinout, SN74CBT6845CPWR application, or SN74CBT6845CPWR equivalent, key selection criteria include live-insertion noise suppression via BIASV precharge, Ioff partial-power-down support, 0–5-V signal level compatibility, and TSSOP-20 package thermal performance (θJA = 83°C/W).

Technical Context

This device implements eight independent FET transmission gates controlled by a single OE input, enabling or disabling bidirectional signal paths between A and B ports. Its active undershoot-protection circuitry senses sub-0-V events and forces OFF-state isolation without latch-up risk.

The B port is internally precharged to BIASV through a 10-kΩ equivalent resistor during power-down or high-OE states, minimizing live-insertion glitches. Ioff functionality ensures no backflow current when VCC = 0 V, supporting true partial-power-down operation per JESD 78 Class II.

Key Specifications

Pinout & Package

TSSOP-20 package (PW), 6.5 mm × 4.4 mm × 1.2 mm max height, exposed leadframe, moisture sensitivity level 1 (260°C peak reflow), RoHS-compliant NiPdAu finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bus switch applications.

Compared with SN74CBT6845CPWR, SN74CBTD6800CPWR trades hot-plug capability for lower-voltage compatibility, while SN74CB3Q3245PWR prioritizes per-channel flexibility and lower ron at the expense of BIASV-based glitch suppression - making SN74CBT6845CPWR uniquely suited for PCI-compliant hot-swap isolation.

Availability

SN74CBT6845CPWR is available at Aetrix Electronics and suitable for PCI hot-plug interfaces, memory interleaving systems, and industrial I/O module bus gating requiring stable component supply and long-term lifecycle continuity.

Supply support for SN74CBT6845CPWR 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 50 years of innovation in high-reliability interface solutions.

The SN74CBT6845CPWR belongs to TI's CBT (Crosspoint Bus Transceiver) family, engineered specifically for high-speed, low-distortion bus isolation in hot-plug-capable computing and telecom infrastructure.

FAQ

What is the function of the BIASV pin on the SN74CBT6845CPWR?

The BIASV pin on the SN74CBT6845CPWR supplies a user-selectable bias voltage (0 V to VCC) that precharges the B-port pins through an internal 10-kΩ equivalent resistor when OE is high or VCC = 0 V. This precharge minimizes live-insertion noise by holding B-port voltages near the input threshold of downstream receivers, preventing false triggering during card mating. The SN74CBT6845CPWR relies on this feature for PCI hot-plug compliance.

Does the SN74CBT6845CPWR support partial-power-down operation?

Yes, the SN74CBT6845CPWR fully supports partial-power-down operation via its Ioff feature. When VCC = 0 V, the device limits backflow current to ≤10 µA, preventing damaging current from flowing into or out of powered-down sections of the system. This behavior is verified per JESD 78 Class II latch-up standards and is essential for safe hot-swap in multi-rail environments using the SN74CBT6845CPWR.

What is the maximum undershoot voltage the SN74CBT6845CPWR can tolerate on its A and B ports?

The SN74CBT6845CPWR provides active undershoot protection up to −2 V on both A and B ports, as confirmed in its absolute maximum ratings and functional description. This protection operates independently of VCC and remains effective even during power-down states, ensuring the switch stays in the proper OFF state during transient negative excursions - a critical capability for the SN74CBT6845CPWR in PCI hot-plug applications.

Can the SN74CBT6845CPWR interface with 1.8-V logic while powered from a 5-V supply?

Yes, the SN74CBT6845CPWR supports 0–5-V signaling on its data I/Os (A and B ports), meaning it can safely pass 1.8-V logic levels while operating from a 4–5.5-V VCC supply. Control inputs (OE) accept TTL or 5-V/3.3-V CMOS levels, and no level-shifting circuitry is required. This voltage flexibility is a defined specification of the SN74CBT6845CPWR and enables mixed-voltage bus architectures.

What is the thermal resistance (θJA) of the SN74CBT6845CPWR in its TSSOP-20 package?

The SN74CBT6845CPWR in the TSSOP-20 (PW) package has a junction-to-ambient thermal resistance (θJA) of 83°C/W, as specified in the device's absolute maximum ratings table. This value assumes standard JEDEC high-K test board conditions and informs thermal design margining for continuous operation at full load. The SN74CBT6845CPWR's low ICC (3 µA max) minimizes self-heating, making this θJA value sufficient for most industrial and computing applications.