Microchip PIC16F687-E/SS 8-Bit Microcontroller: Features and Application Design Guide
The Microchip PIC16F687-E/SS is a versatile 8-bit microcontroller built on PIC® architecture, offering a robust set of peripherals in a compact 20-pin SSOP package. It is engineered for cost-sensitive, space-constrained applications requiring high performance and low power consumption. This guide explores its key features and provides essential design considerations for integrating it into new projects.
Key Features of the PIC16F687-E/SS
At its core, the device operates at up to 20 MHz with an internal oscillator, delivering 5 MIPS of performance. This eliminates the need for an external crystal for many applications, reducing both component count and board space. Its 2 KB of Flash program memory and 128 bytes of RAM are well-suited for a multitude of control-oriented tasks.
A standout feature is its rich set of integrated peripherals:
Analog-to-Digital Converter (ADC): A 10-bit ADC with 11 channels provides extensive capability for sensing analog signals from sensors for temperature, voltage, or pressure.
Enhanced Capture/Compare/PWM (ECCP) Module: This offers flexible Pulse-Width Modulation for precise control of devices like motors, LEDs, and fans.
Comparator Module: An analog comparator with programmable voltage reference simplifies external analog signal conditioning.
Enhanced Universal Synchronous Asynchronous Receiver Transmitter (EUSART): This supports both RS-232 and RS-485 protocols, enabling seamless serial communication with PCs, peripherals, or other microcontrollers.
In-Circuit Serial Programming™ (ICSP™): This allows for easy firmware updates and debugging without removing the microcontroller from the circuit board.
Furthermore, it boasts nanowatt-level power management technology, enabling the design of highly efficient, battery-powered products through multiple selectable sleep modes.
Application Design Guide
1. Power Supply Decoupling: Place a 100nF ceramic decoupling capacitor as close as possible to the VDD and VSS pins. For environments with significant power supply noise, a larger bulk capacitor (e.g., 10µF) is also recommended.
2. Programming Interface: Allocate pins for the ICSP™ interface (PGC, PGD, and MCLR/VPP). Ensure the MCLR pin is properly pulled up to VDD through a resistor (e.g., 10kΩ) if used as a reset pin.
3. Analog Design Considerations: When using the ADC, ensure a stable analog reference voltage. Use a dedicated, filtered power supply trace for analog components to minimize digital switching noise. Employ the internal ADC module’s acquisition time settings correctly to ensure accurate sampling.
4. Oscillator Configuration: The internal oscillator is often sufficient. If higher precision is required, an external crystal or resonator can be used on the OSC1/CLKIN and OSC2/CLKOUT pins.
5. I/O Pin Management: Configure unused I/O pins as outputs and drive them to a low state, or configure them as inputs and enable weak pull-ups to prevent floating inputs, which consume excess power.
6. Communication Interfaces: For RS-485 networks using the EUSART, implement proper termination resistors and consider using a transceiver IC with built-in fail-safe bias and protection.
Typical Applications
This microcontroller is ideal for a wide range of applications, including:
Sensor Interface and Data Logging Nodes
Consumer Appliances (e.g., coffee makers, remote controls)
Automotive Accessories (e.g, sensors, lighting control)
Industrial Control (e.g., actuators, pumps, fans)
Low-Power Battery-Powered Devices
The PIC16F687-E/SS stands out as a highly integrated and cost-effective solution for embedded control. Its combination of a powerful 10-bit ADC, versatile communication peripherals like EUSART, and robust nanowatt power management makes it an excellent choice for designers tackling complex analog and digital control tasks within a tight power and space budget.
Keywords: 8-Bit Microcontroller, PIC16F687, Analog-to-Digital Converter (ADC), EUSART, Low-Power Design.
