SN74LS138DR 3-LINE TO 8-LINE DECORDERS/DEMULTIPLEXERS ic circuit board

FEATURES

• High-Bandwidth Data Path (up to 500 MHz (1) )

•5-V Tolerant I/Os With Device Powered Up or Powered Down

•Low and Flat ON-State Resistance (r on)Characteristics Over Operating Range (r on = 4 Ω Typ)

• Rail-to-Rail Switching on Data I/O Ports 0- to 5-V Switching With 3.3-V VCC – 0- to 3.3-V Switching With 2.5-V V Operation CC

•Bidirectional Data Flow With Near-Zero Propagation Delay

•Low Input/Output Capacitance Minimizes Loading and Signal Distortion (Cio(OFF) = 3.5 pF Typ)

• Fast Switching Frequency (f OE = 20 MHz Max)

DESCRIPTION/ORDERING INFORMATION (CONTINUED)

The SN74CB3Q3257 is a high-bandwidth FET bus switch utilizing a charge pump to elevate the gate voltage of the pass transistor, providing a low and flat ON-state resistance (r on). The low and flat ON-state resistance allows for minimal propagation delay and supports rail-to-rail switching on the data input/output (I/O) ports. The device also features low data I/O capacitance to minimize capacitive loading and signal distortion on the data bus. Specifically designed to support high-bandwidth applications, the SN74CB3Q3257 provides an optimized interface solution ideally suited for broadband communications, networking, and data-intensive computing systems

The SN74CB3Q3257 is a 4-bit 1-of-2 high-speed FET multiplexer/demultiplexer with a single output-enable (OE) input. The select (S) input controls the data path of the multiplexer/demultiplexer. When OE is low, the multiplexer/demultiplexer is enabled and the A port is connected to the B port, allowing bidirectional data flow between ports. When OE is high, the multiplexer/demultiplexer is disabled and a high-impedance state exists between the A and B ports

This device is fully specified for partial-power-down applications using I off . The I off circuitry prevents damaging current 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.

Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)

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