SN74CBT6845C中文资料具有预充电输出和 –2V 下冲保护的 5V、1:1 (SPST)、8 通道 FET 总线开关数据手册TI规格书

描述 Description

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.

特性 Features

• Undershoot Protection for Off-Isolation on A and B Ports Up To –2 V
• Supports PCI Hot Plug
• Low ON-State Resistance (ron) Characteristics (ron = 3 Typical)
• Data and Control Inputs Provide Undershoot Clamp Diodes
• VCC Operating Range From 4 V to 5.5 V
• Control Inputs Can be Driven by TTL or 5-V/3.3-V CMOS Outputs
• Latch-Up Performance Exceeds 100 mA Per JESD 78, Class II
• 2000-V Human-Body Model (A114-B, Class II)
• Supports Both Digital and Analog Applications: PCI Interface, Memory Interleaving, Bus Isolation, Low-Distortion Signal Gating

简介

SN74CBT6845C属于集成电路（IC）的信号开关多路复用器解码器。由TI制造生产的SN74CBT6845C信号开关，多路复用器，解码器逻辑型信号开关、多路复用器和编码器 IC 可用于对以数字格式表示数据的电信号进行路由和选择。这些器件与设计用于模拟信号的类似产品有所不同，它们保留的信息表示为两个电状态之一，而不是两个外部界限内的无穷变化量。