SN74LVC646A
OCTAL BUS TRANSCEIVER AND REGISTER
WITH 3-STATE OUTPUTS

SCAS302C - JANUARY 1993 - REVISED JANUARY 1997

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features

• EPIC^TM (Enhanced-Performance Implanted CMOS) Submicron Process
• Typical V_OLP (Output Ground Bounce) < 0.8 V at V_CC = 3.3 V, T_A = 25°C
• Typical V_OHV (Output V_OH Undershoot) > 2 V at V_CC = 3.3 V, T_A = 25°C
• Supports Mixed-Mode Signal Operation on All Ports (5-V Input/Output Voltage With 3.3-V V_CC)
• Package Options Include Plastic Small-Outline (DW), Shrink Small-Outline (DB), and Thin Shrink Small-Outline (PW) Packages

EPIC is a trademark of Texas Instruments Incorporated.

description

This octal bus transceiver and register is designed for 2.7-V to 3.6-V V_CC operation.

The SN74LVC646A consists of bus-transceiver circuits, D-type flip-flops, and control circuitry arranged for multiplexed transmission of data directly from the input bus or from the internal registers. Data on the A or B bus is clocked into the registers on the low-to-high transition of the appropriate clock (CLKAB or CLKBA) input. Figure 1 illustrates the four fundamental bus-management functions that can be performed with the SN74LVC646A.

Output-enable () and direction-control (DIR) inputs control the transceiver functions. In the transceiver mode, data present at the high-impedance port can be stored in either register or in both.

The select-control (SAB and SBA) inputs can multiplex stored and real-time (transparent mode) data. DIR determines which bus receives data when is low. In the isolation mode ( high), A data can be stored in one register and B data can be stored in the other register.

When an output function is disabled, the input function is still enabled and can be used to store and transmit data. Only one of the two buses, A or B, can be driven at a time.

Inputs can be driven from either 3.3-V or 5-V devices. This feature allows the use of these devices as translators in a mixed 3.3-V/5-V system environment.

To ensure the high-impedance state during power up or power down, should be tied to V_CC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

The SN74LVC646A is characterized for operation from -40°C to 85°C.