CY74FCT646T Octal Registered Bus Transceivers with 3-State Outputs |


Octal Registered Bus Transceivers with 3-State Outputs



The \x92FCT646T devices consist of a bus transceiver circuit with 3-state, 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 as the appropriate clock pin goes to a high logic level. Output-enable (G\) and direction (DIR) inputs control the transceiver function. In the transceiver mode,data present at the high-impedance port can be stored in either the A or B register, or in both. Select controls (SAB, SBA) can multiplex stored and real-time (transparent mode) data. DIR determines which bus receives data when G\ is low. In the isolation mode (G\ is high), A data can be stored in the B register and/or B data can be stored in the A register.

These devices are fully specified for partial-power-down applications using Ioff. The Ioff circuitry disables the outputs, preventing damaging current backflow through the device when it is powered down.


  • Function, Pinout, and Drive Compatible With FCT and F Logic
  • Reduced VOH (Typically = 3.3 V) Versions of Equivalent FCT Functions
  • Edge-Rate Control Circuitry for Significantly Improved Noise Characteristics
  • Ioff Supports Partial-Power-Down Mode Operation
  • Matched Rise and Fall Times
  • Fully Compatible With TTL Input and Output Logic Levels
  • ESD Protection Exceeds JESD 22
    • 2000-V Human-Body Model (A114-A)
    • 200-V Machine Model (A115-A)
    • 1000-V Charged-Device Model (C101)
  • Independent Register for A and B Buses
  • CY54FCT646T
    • 48-mA Output Sink Current
    • 12-mA Output Source Current
  • CY74FCT646T
    • 64-mA Output Sink Current
    • 32-mA Output Source Current
  • 3-State Outputs

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Parametrics Compare all products in Registered transceiver

Technology Family
VCC (Min) (V)
VCC (Max) (V)
Bits (#)
Voltage (Nom) (V)
F @ nom voltage (Max) (Mhz)
ICC @ nom voltage (Max) (mA)
tpd @ Nom Voltage (Max) (ns)
IOL (Max) (mA)
IOH (Max) (mA)
Operating temperature range (C)
Package Group
FCT     FCT     FCT     FCT    
4.75     4.75     4.75     4.75    
5.25     5.25     5.25     5.25    
8     8     8     8    
5     5     5     5    
70     70     70     70    
0.2     0.2     0.2     0.2    
6.3     5.4     9     9    
64     64     64     64    
-32     -32     -32     -32    
-40 to 85     -40 to 85     -40 to 85     -55 to 125    
SOIC | 24
SSOP | 24    
SOIC | 24     SOIC | 24     LCCC | 28