SN74ALS29821 10-bit Bus Interface Flip-Flops With 3-State Outputs |

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10-bit Bus Interface Flip-Flops With 3-State Outputs



These 10-bit edge-triggered D-type flip-flops feature 3-state outputs designed specifically for driving highly capacitive or relatively low-impedance loads. These devices are particularly suitable for implementing wider buffer registers, I/O ports, bidirectional bus drivers with parity, and working registers.

On the positive transition of the clock (CLK) input, the Q outputs are true to the data (D) input.

A buffered output-enable () input can place the ten outputs in either a normal logic state (high or low logic levels) or a high-impedance state. The outputs also are in the high-impedance state during power-up and power-down conditions. The outputs remain in the high-impedance state while the device is powered down. 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 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.

The SN54ALS29821 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ALS29821 is characterized for operation from 0°C to 70°C.




  • Functionally Equivalent to AMD's AM29821
  • Provide Extra Data Width Necessary for Wider Address/Data Paths or Buses With Parity
  • Outputs Have Undershoot-Protection Circuitry
  • Power-Up High-Impedance State
  • Buffered Control Inputs Reduce dc Loading Effects
  • Package Options Include Plastic Small-Outline (DW) Packages and Standard Plastic (NT) and Ceramic (JT) 300-mil DIPs



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Part number Order Technology Family Input type Output type VCC (Min) (V) VCC (Max) (V) IOL (Max) (mA) IOH (Max) (mA) Rating Package Group
SN74ALS29821 Order now ALS     TTL     TTL     4.75     5.25     48     -24     Catalog     SOIC | 24    
SN54ALS29821 Samples not available ALS     TTL     TTL     4.75     5.25     48     -24     Military     CDIP | 24