描述 Description

These 20-bit flip-flops feature 3-state outputs designed specifically for driving highly capacitive or relatively low-impedance loads. They are particularly suitable for implementing wider buffer registers, I/O ports, bidirectional bus drivers with parity, and working registers.
The 'ABT16821 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) input, the device provides true data 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 logic 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.
To ensure the high-impedance state during power up or power down, 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.
The SN54ABT16821 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ABT16821 is characterized for operation from -40°C to 85°C.
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特性 Features

? Members of the Texas Instruments WidebusTM Family
? State-of-the-Art EPIC-IIBTM BiCMOS DesignSignificantly Reduces Power Dissipation
? ESD Protection Exceeds 2000 V Per MIL-STD-883, Method 3015;Exceeds 200 V Using Machine Model (C = 200 pF, R = 0)
? Typical VOLP (Output Ground Bounce) CC = 5 V, TA = 25°C
? Distributed VCC and GND Pin Configuration MinimizesHigh-Speed Switching Noise
? Flow-Through Architecture Optimizes PCB Layout
? High-Drive Outputs (-32-mA IOH, 64-mAIOL)
? Package Options Include Plastic Thin Shrink Small-Outline(DGG), 300-mil Shrink Small-Outline (DL) Packages and 380-milFine-Pitch Ceramic Flat (WD) Package Using 25-mil Center-to-CenterSpacingsWidebus and EPIC-IIB are trademarks of Texas InstrumentsIncorporated.