Overview
The MC74AC138DR2, produced by onsemi, is a high-speed 1-of-8 decoder/demultiplexer. This device is particularly suited for high-speed bipolar memory chip select address decoding. It features three binary weighted address inputs (A0, A1, A2) and provides eight mutually exclusive active-LOW outputs (O0-O7). The device also includes three enable inputs: two active-LOW (E1, E2) and one active-HIGH (E3), which allow for easy parallel expansion and various control functions.
Key Specifications
| Parameter | Value | Unit | Conditions |
|---|---|---|---|
| DC Supply Voltage (VCC) | 2.0 to 6.0 | V | |
| DC Input Voltage (VI) | -0.5 to VCC + 0.5 | V | |
| DC Output Voltage (VO) | -0.5 to VCC + 0.5 | V | |
| Operating Ambient Temperature Range (TA) | -40 to 85 | °C | |
| Output Current - High (IOH) | -24 | mA | |
| Output Current - Low (IOL) | 24 | mA | |
| Propagation Delay An to On | 6.5 to 15.0 | ns | VCC = 5.0 V, CL = 50 pF |
| Input Capacitance (CIN) | 4.5 | pF | VCC = 5.0 V |
| Power Dissipation Capacitance (CPD) | 60 | pF | VCC = 5.0 V |
Key Features
- Demultiplexing capability
- Multiple input enables for easy expansion (allows parallel expansion to a 1-of-24 or 1-of-32 decoder)
- Active LOW mutually exclusive outputs
- Outputs source/sink 24 mA
- TTL compatible inputs for the MC74ACT138 version
- Pb-Free devices
Applications
The MC74AC138DR2 is ideal for high-speed bipolar memory chip select address decoding. It can be used in various applications such as:
- Memory address decoding
- Demultiplexing functions
- Cascading and chip-selecting functions
- High-speed digital systems requiring low propagation delays
Q & A
- What is the primary function of the MC74AC138DR2?
The primary function is to act as a 1-of-8 decoder/demultiplexer, suitable for high-speed bipolar memory chip select address decoding. - How many address inputs does the MC74AC138DR2 have?
The device has three binary weighted address inputs (A0, A1, A2). - What are the types of enable inputs on the MC74AC138DR2?
The device features two active-LOW enable inputs (E1, E2) and one active-HIGH enable input (E3). - Can the MC74AC138DR2 be expanded for more outputs?
Yes, it can be expanded to a 1-of-24 or 1-of-32 decoder using multiple devices and an inverter. - What is the operating voltage range for the MC74AC138DR2?
The operating voltage range is 2.0 to 6.0 V. - What is the maximum output current for the MC74AC138DR2?
The outputs can source or sink up to 24 mA. - Is the MC74AC138DR2 Pb-Free?
Yes, the device is Pb-Free. - What are the typical propagation delays for the MC74AC138DR2?
The propagation delays range from 6.5 to 15.0 ns depending on the VCC and load conditions. - Can the MC74AC138DR2 be used as a demultiplexer?
Yes, it can be used as an 8-output demultiplexer by using one of the active LOW Enable inputs as the data input and the other Enable inputs as strobes. - What are the package options for the MC74AC138DR2?
The device is available in SOIC-16 and TSSOP-16 packages.
