U74CB3Q3257

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CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 9

www.unisonic.com.tw

QW-R502-D36.a

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DETAILED DESCRIPTION

Overview

The UTC U74CB3Q3257 device is a high-bandwidth FET bus switch using a charge pump to elevate the gate

voltage of the pass transistor, providing a low and flat ON-state resistance (ron). 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 UTC U74CB3Q3257 device provides an

optimized interface solution ideally suited for broadband communications, networking, and data-intensive computing

systems.

The UTC U74CB3Q3257 device is organized as two1-of-4 multiplexers/ demultiplexers with separate

output-enable(1OE,2OE)inputs. The select (S0, S1) inputs control the data path of each multiplexer/demultiplexer.

When OE is low, the associated 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 associated 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 Ioff. The Ioff circuitry prevents damaging

current back flow 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 pull up

resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

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FEATURE DESCRIPTION

The UTC U74CB3Q3257 device has a high-bandwidth data path(up to 500MHz) and has 5Vtolerant I/Os with the

device powered up or powered down. It also has low and flat ON-state resistance (RON) characteristics over

operating range (RON =4Ω Typ.).

This device also has rail-to-rail switching on data I/O ports for 0 to 5V switching with 3.3V VCC and 0 to 3.3V

switching with 2.5V VCC as well as bidirectional data flow with near-zero propagation delay and low input/output

capacitance that minimizes loading and signal distortion (CIO(OFF)=3.5pF Typ.).

The UTC U74CB3Q3257 also provides a fast switching frequency (fOE=20MHz Max.)with data and control inputs

that provide undershoot clamp diodes as well as low power consumption (ICC=0.6mA Typ.).

The VCC operating range is from 2.3V to 3.6V and the data I/Os support 0 to 5V signal levels of (0.8V, 0.2V,1.5V,

1.8V, 2.5V, 3.3V, 5V).

The control inputs can be driven by TTL or 5V/3.3V CMOS outputs as well as Ioff Supports Partial-Power-Down

Mode Operation

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DEVICE FUNCTIONAL MODES

INPUTS

INPUT/OUTPUT

A

FUNCTION

OE

S

L

L

B1

A port = B1 port

L

H

B2

A port = B2 port

H

X

Hi-Z

Disconnect

Note: H=High Voltage Level, L=Low Voltage Level, Hi-Z: High-Impedance.

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APPLICATION INFORMATION

The UTC U74CB3Q3257 can be used to multiplex and demultiplex up to 4 channels simultaneously in a 2:1

configuration. The application shown here is a4-bit bus being multiplexed between two devices. the OE and S pins

are used to control the chip from the bus controller. This is a very generic example, and could apply to many

situations. If an application requires less than 4 bits, be sure to tie the Aside to either high or low on unused

channels.