SN54LVT646, SN74LVT646
3.3-V ABT OCTAL BUS TRANSCEIVERS AND REGISTERS
WITH 3-STATE OUTPUTS

SCBS140D - MAY 1992 - REVISED JULY 1995

features

• State-of-the-Art Advanced BiCMOS Technology (ABT) Design for 3.3-V Operation and Low Static Power Dissipation
• Support Mixed-Mode Signal Operation (5-V Input and Output Voltages With 3.3-V V_CC)
• Support Unregulated Battery Operation Down to 2.7 V
• Typical V_OLP (Output Ground Bounce)< 0.8 V at V_CC = 3.3 V, T_A = 25°C
• ESD Protection Exceeds 2000 V Per MIL-STD-883C, Method 3015; Exceeds 200 V Using Machine Model (C = 200 pF, R = 0)
• Latch-Up Performance Exceeds 500 mA Per JEDEC Standard JESD-17
• Bus-Hold Data Inputs Eliminate the Need for External Pullup Resistors
• Support Live Insertion
• Package Options Include Plastic Small-Outline (DW), Shrink Small-Outline (DB), and and Thin Shrink Small-Outline (PW) Packages, Ceramic Chip Carriers (FK), Ceramic Flat (W) Packages, and Ceramic (JT) DIPs

description

These bus transceivers and registers are designed specifically for low-voltage (3.3-V) V_CC operation, but with the capability to provide a TTL interface to a 5-V system environment.

The 'LVT646 consist 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 ´LVT646.

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

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

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

Active bus-hold circuitry is provided to hold unused or floating data inputs at a valid logic level.

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 SN74LVT646 is available in TI's shrink small-outline package (DB), which provides the same I/O pin count and functionality of standard small-outline packages in less than half the printed-circuit-board area.

The SN54LVT646 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74LVT646 is characterized for operation from -40°C to 85°C.