Overview
The CD74AC138ME4, produced by Texas Instruments, is a 3-line to 8-line decoder/demultiplexer designed for high-performance memory-decoding and data-routing applications. This device is part of the AC series, which features balanced noise immunity and significantly reduced power consumption. It is particularly suited for high-speed memory systems where short propagation-delay times are crucial.
Key Specifications
| Parameter | Min | Max | Unit |
|---|---|---|---|
| Supply Voltage Range (VCC) | -0.5 | 6 | V |
| Input Clamp Current (IIK) | -20 | 20 | mA |
| Output Clamp Current (IOK) | -50 | 50 | mA |
| Continuous Output Current (IO) | -50 | 50 | mA |
| Storage Temperature Range (Tstg) | -65 | 150 | °C |
| High-Level Output Current (IOH) at VCC = 4.5 V to 5.5 V | -24 | -24 | mA |
| Low-Level Output Current (IOL) at VCC = 4.5 V to 5.5 V | 24 | 24 | mA |
| Propagation Delay Time (tPLH) at VCC = 5 V, CL = 50 pF | 2.8 | 11 | ns |
| Junction-to-Ambient Thermal Resistance (RθJA) for TSSOP Package | 126.2 | °C/W |
Key Features
- Operates over a wide voltage range of 1.5V to 5.5V with balanced noise immunity at 30% of the supply voltage.
- High-speed operation with reduced power consumption, suitable for bipolar F, AS, and S types.
- Incorporates three enable inputs to simplify cascading and data reception.
- Balanced propagation delays and ±24mA output drive current, allowing fanout to 15 F devices.
- SCR-latchup-resistant CMOS process and circuit design.
- Exceeds 2kV ESD protection per MIL-STD-883, method 3015.
- Available in various packages including SOIC, PDIP, TSSOP, and WQFN.
Applications
The CD74AC138ME4 is primarily used in high-performance memory-decoding and data-routing applications. It is particularly useful in:
- High-speed memory systems to minimize the effects of system decoding.
- Data-transmission systems requiring short propagation-delay times.
- Cascaded decoder/demultiplexer configurations.
Q & A
- What is the operating voltage range of the CD74AC138ME4? The CD74AC138ME4 operates over a voltage range of 1.5V to 5.5V.
- What are the key features of the CD74AC138ME4? Key features include high-speed operation, balanced noise immunity, three enable inputs, balanced propagation delays, and high output drive current.
- What are the different package options available for the CD74AC138ME4? The device is available in SOIC, PDIP, TSSOP, and WQFN packages.
- What is the maximum output current of the CD74AC138ME4? The maximum output current is ±50 mA.
- How does the CD74AC138ME4 protect against ESD? The device exceeds 2kV ESD protection per MIL-STD-883, method 3015.
- What is the significance of the three enable inputs in the CD74AC138ME4? The three enable inputs simplify cascading and data reception.
- What are the thermal characteristics of the CD74AC138ME4? The junction-to-ambient thermal resistance varies by package, with the TSSOP package having a resistance of 126.2 °C/W.
- How should unused inputs be handled in the CD74AC138ME4? Unused inputs must be connected to either VCC or GND to prevent floating and ensure proper device operation.
- What are the power supply recommendations for the CD74AC138ME4? Each VCC terminal should have a good bypass capacitor, typically a 0.1μF capacitor, to prevent power disturbances.
- What are the typical propagation delay times for the CD74AC138ME4? The propagation delay times range from 2.8 ns to 11 ns at VCC = 5 V and CL = 50 pF.
