CD74HC640 - High Speed CMOS Logic Octal Inverting Bus Transceivers with 3-State Outputs

The ’HC640 and ’HCT640 silicon-gate CMOS three-state bidirectional inverting and non-inverting buffers are intended for two-way asynchronous communication between data buses. They have high drive current outputs which enable high-speed operation when driving large bus capacitances. These circuits possess the low power dissipation of CMOS circuits, and have speeds comparable to low power Schottky TTL circuits. They can drive 15 LSTTL loads. The ’HC640 and ’HCT640 are inverting buffers.

The direction of data flow (A to B, B to A) is controlled by the DIR input.

Outputs are enabled by a low on the Output Enable input (OE\); a high OE\ puts these devices in the high impedance mode.

• Buffered Inputs
• Three-State Outputs
• Applications in Multiple-Data-Bus Architecture
• Fanout (Over Temperature Range)
  • Standard Outputs. . . . . . . . . . . . . . . 10 LSTTL Loads
  • Bus Driver Outputs . . . . . . . . . . . . . 15 LSTTL Loads
• Wide Operating Temperature Range . . . -55°C to 125°C
• Balanced Propagation Delay and Transition Times
• Significant Power Reduction Compared to LSTTL Logic ICs
• HC Types
  • 2V to 6V Operation
  • High Noise Immunity: N_IL = 30%, N_IH = 30% of V_CC at V_CC = 5V
• HCT Types
  • 4.5V to 5.5V Operation
  • Direct LSTTL Input Logic Compatibility, V_IL = 0.8V (Max), V_IH = 2V (Min)
  • CMOS Input Compatibility, I_l ≤ 1µA at V_OL, V_OH