SN54ALVTH16821, SN74ALVTH16821
2.5-V/3.3-V 20-BIT BUS-INTERFACE FLIP-FLOPS
WITH 3-STATE OUTPUTS

SCES078A - JULY 1996 - REVISED JULY 1996

features

• Members of the Texas Instruments Widebus^TM Family
• High-Impedance State During Power Up and Power Down
• 5-V I/O Compatible
• High-Drive Capability (-32 mA/64 mA)
• Typical V_OLP (Output Ground Bounce) < 0.8 V at V_CC = 3.3 V, T_A = 25°C
• Auto 3-State Eliminates Bus Current Loading When Voltage at the Output Exceeds V_CC
• Bus-Hold Data Inputs Eliminate the Need for External Pullup/Pulldown Resistors
• Power Off Disables Inputs/Outputs, Permitting Live Insertion
• Package Options Include Plastic 300-mil Shrink Small-Outline (DL), Thin Shrink Small-Outline (DGG), Thin Very Small-Outline (DGV) Packages, and 380-mil Fine-Pitch Ceramic Flat (WD) Package

  Widebus is a trademark of Texas Instruments Incorporated.

description

The 'ALVTH16821 are 20-bit bus-interface flip-flops with 3-state outputs designed for 2.5-V or 3.3-V V_CC operation, but with the capability to provide a TTL interface to a 5-V system environment.

The 'ALVTH16821 can be used as two 10-bit flip-flops or one 20-bit flip-flop. The 20 flip-flops are edge-triggered D-type flip-flops. On the positive transition of the clock (CLK), the flip-flops store the logic levels set up at the Q outputs.

A buffered output-enable input can be used to place the ten outputs in either a normal logic state (high or low level) or a high-impedance state. In the high-impedance state, the outputs neither load nor drive the bus lines significantly. The high-impedance state and increased drive provide the capability to drive bus lines without need for interface or pullup components.

does not affect the internal operation of the flip-flops. Old data can be retained or new data can be entered while the outputs are in the high-impedance state.

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

When V_CC is between 0 and 1.2 V, the device is in the high-impedance state during power up or power down. However, to ensure the high-impedance state above 1.2 V, 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 SN74ALVTH16821 is available in TI's thin very small-outline package (DGV), which provides the same I/O pin count and functionality of standard Widebus packages in less than half the printed circuit board area.

The SN54ALVTH16821 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ALVTH16821 is characterized for operation from -40°C to 85°C.