Unlocking the Power of Serial-to-Parallel Conversion: The onsemi MC74HC164ADR2G
In the realm of digital electronics, efficiently managing multiple output signals with a minimal number of microcontroller pins is a common challenge. The onsemi MC74HC164ADR2G provides an elegant and cost-effective solution. This integrated circuit is a high-speed 8-bit serial-in/parallel-out shift register, a fundamental building block for expanding digital I/O capabilities. Utilizing advanced High-Speed CMOS technology, it offers the low power consumption of CMOS logic while maintaining the high output drive and speed similar to LSTTL logic.
This article delves into the datasheet specifications, pinout configuration, and practical application circuits for this versatile IC.
Datasheet Overview and Key Specifications
The MC74HC164ADR2G is characterized by its wide operating voltage range of 2.0 V to 6.0 V, making it compatible with various logic levels, including 3.3V and 5V systems. Its key electrical characteristics include:
High Noise Immunity: Standard for CMOS devices.
Low Power Consumption: Typical ICC of 4 μA (static).
High Output Current: Able to sink or source up to 5.2 mA at 5V, sufficient to drive LEDs or other low-power loads directly.
Fast Operating Frequency: Typically 70 MHz at 4.5V.
The device features two serial data inputs (A1 and A2) that are ANDed together internally. This allows for easy control of data entry by using one input as an active-high enable. A low-level asynchronous Master Reset (MR) pin clears the register, setting all outputs (Q0 to Q7) to low, regardless of the clock or input conditions. The serial data is shifted on the low-to-high transition of the clock pulse (CP).
Pinout Configuration
The MC74HC164ADR2G is available in a 14-pin SOIC package. Its pinout is as follows:
Pin 1 (A1): Serial Data Input 1
Pin 2 (A2): Serial Data Input 2
Pin 3 (Q0): Parallel Output 0 (LSB)
Pins 4, 5, 6, 7, 8, 9 (Q1 - Q6): Parallel Outputs 1 through 6
Pin 10 (Q7): Parallel Output 7 (MSB)
Pin 11 (CP): Clock Input (Positive-edge triggered)
Pin 12 (MR): Master Reset (Active LOW)
Pin 13 (GND): Ground (0V)
Pin 14 (VCC): Positive Supply Voltage (2.0V to 6.0V)
Practical Application Circuits
1. Basic LED Driver/Display:
The most common use is driving an array of 8 LEDs with just three microcontroller pins (Data, Clock, and Reset). The microcontroller sends data serially, one bit per clock cycle. After 8 clock cycles, the byte appears on the parallel outputs, lighting the corresponding LEDs. This is a simple and effective way to create status displays or bar graphs.
2. I/O Port Expansion:
When a project requires more digital outputs than a microcontroller can provide, multiple MC74HC164s can be daisy-chained to create a virtually unlimited number of outputs. The Q7 output (MSB) of the first shift register is connected to the serial data input of the next one. By sending 16 bits of data for two registers (or more for more registers), the system can control 16 or more outputs using the same three microcontroller pins.
3. Serial-to-Parallel Data Conversion:
The IC is essential for interfacing serial communication protocols (like a microcontroller's SPI bus) with devices that require a parallel data input, such as older digital-to-analog converters (DACs) or for setting control registers on other peripherals.
ICGOODFIND: The onsemi MC74HC164ADR2G is an exceptionally useful and robust shift register that remains a go-to component for designers. Its primary value lies in its ability to significantly expand output capabilities using a minimal number of microcontroller GPIO pins. Its high-speed operation, low power consumption, and simple 3-wire interface make it ideal for a vast array of applications, from simple LED displays and control systems to more complex serial-to-parallel data conversion tasks. For anyone looking to manage multiple outputs efficiently, the MC74HC164 is a fundamental and highly recommended part.
Keywords: Shift Register, Serial-to-Parallel, I/O Expansion, LED Driver, HC164.
