The TC74VHC138FT is a high-speed CMOS logic 3-to-8 line decoder manufactured by Toshiba Semiconductor and Storage. This device utilizes silicon gate CMOS technology to achieve high-speed operation similar to equivalent Bipolar Schottky TTL devices, while maintaining the low power consumption inherent in CMOS integrated circuits. The TC74VHC138FT accepts three binary weighted inputs (A0, A1, and A2) and, depending upon the state of these inputs, provides one of eight mutually exclusive outputs which are active LOW.

Applications

• Memory address decoding
• Data routing
• Demultiplexing applications
• Logic pattern generation

Features

• High-speed operation: tpd = 4.5 ns (typ.) at VCC = 5 V
• Low power dissipation: ICC = 4 μA (max) at Ta = 25°C
• High noise immunity: VNIH = VNIL = 28 % VCC (min)
• Output drive capability: 10 LSTTL loads
• Symmetrical output impedance: |IOH| = IOL = 8 mA (min)
• Balanced propagation delays: tPLH ≈ tPHL
• Wide operating voltage range: VCC = 2 V to 5.5 V
• Pin and function compatible with 74HC138

Benefits

• Increased system performance due to high-speed operation.
• Reduced power consumption leading to longer battery life in portable devices.
• Improved noise immunity ensures reliable operation in noisy environments.
• Ability to drive a large number of loads simplifies system design.
• Symmetrical output impedance minimizes signal distortion.
• Balanced propagation delays ensure accurate timing.
• Wide operating voltage provides flexibility in power supply design.

Additional Details

The TC74VHC138FT also features three enable inputs (E1, E2, and E3). E1 and E2 are active LOW enables, and E3 is an active HIGH enable. All three enables must be satisfied for proper decoding. If any enable is not satisfied, all eight outputs will be HIGH. This device is supplied in a TSSOP package and is suitable for surface mount applications. The operating temperature range is -40°C to 85°C.

The inputs are equipped with protection circuits against static discharge or transient excess voltage. This ensures the device is robust and reliable in demanding applications.