The ’HC646 devices consist of bus-transceiver circuits with 3-state outputs, 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 ’HC646 devices.

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

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

To ensure the high-impedance state during power up or power down, OE\ 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.

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

• Wide Operating Voltage Range of 2 V to 6 V
• High-Current 3-State Outputs Can Drive Up To 15 LSTTL Loads
• Low Power Consumption, 80-A Max ICC
• Typical tpd = 11 ns
• ±6-mA Output Drive at 5 V
• Low Input Current of 1 A Max
• Independent Registers for A and B Buses
• Multiplexed Real-Time and Stored Data
• True Data Paths

• IOL (Max) (mA)
• 7.8
• IOH (Max) (mA)
• -7.8
• Technology Family
• HC
• Rating
• Catalog
• Operating temperature range (C)
• -40 to 85

SN74HC646的完整型号有：SN74HC646DW、SN74HC646DWR，以下是这些产品的关键参数及官网采购报价：

SN74HC646DW，工作温度：-40 to 85，封装：SOIC (DW)-24，包装数量MPQ：25个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网SN74HC646DW的批量USD价格：.575（1000+）

SN74HC646DWR，工作温度：-40 to 85，封装：SOIC (DW)-24，包装数量MPQ：2000个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网SN74HC646DWR的批量USD价格：.479（1000+）

14-24-LOGIC-EVM 支持 14 到 24 引脚 PW、DB、D、DW、NS、DYY 和 DGV 封装的通用逻辑 EVM

该 EVM 设计用于支持采用 14 至 24 引脚 D、DW、DB、NS、PW、DYY 或 DGV 封装的任何逻辑器件。