These bus transceivers and registers are designed specifically for low-voltage (3.3-V) V_CC operation, but with the capability to provide a TTL interface to a 5-V system environment.

The ’LVTH646 devices consist of bus transceiver circuits, 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 ’LVTH646.

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

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

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

Active bus-hold circuitry is provided to hold unused or floating data inputs at a valid logic level. Use of pullup or pulldown resistors with the bus-hold circuitry is not recommended.

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.

These devices are fully specified for hot-insertion applications using I_off and power-up 3-state. The I_off circuitry disables the outputs, preventing damaging current backflow through the devices when they are powered down. The power-up 3-state circuitry places the outputs in the high-impedance state during power up and power down, which prevents driver conflict.

• Support Mixed-Mode Signal Operation (5-V Input and Output Voltages With 3.3-V VCC)
• Support Unregulated Battery Operation Down to 2.7 V
• Typical VOLP (Output Ground Bounce) <0.8 V at VCC = 3.3 V, TA = 25°C
• Ioff and Power-Bus Hold on Data Inputs Eliminates the Need for External Pullup/Pulldown Resistors
• Latch-Up Performance Exceeds 500 mA Per JESD 17
• ESD Protection Exceeds JESD 22
  • 2000-V Human-Body Model (A114-A)
  • 200-V Machine Model (A115-A)

• IOL (Max) (mA)
• 64
• IOH (Max) (mA)
• -64
• Technology Family
• LVT
• Rating
• Catalog
• Operating temperature range (C)
• -40 to 85

SN74LVTH646的完整型号有：SN74LVTH646DW、SN74LVTH646PWR，以下是这些产品的关键参数及官网采购报价：

SN74LVTH646DW，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SN74LVTH646DW的批量USD价格：0.424（1000+）

SN74LVTH646PWR，工作温度：-40 to 85，封装：TSSOP (PW)-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SN74LVTH646PWR的批量USD价格：0.424（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。