Empower your electronics with the power of optical isolation based on the LTV-817S and PIC32MZ2048EFM100

Guardian of signals: OptoSentry for total isolation!

Published Sep 21, 2023

Click board™

OPTO 4 Click

Dev. board

Curiosity PIC32 MZ EF

Compiler

NECTO Studio

MCU

PIC32MZ2048EFM100

Achieve cleaner and more reliable signal transmission by isolating your circuits from electrical noise and disturbances

Hardware Overview

How does it work?

Opto 4 Click is based on the LTV-817S, an optocoupler with a high isolation voltage from ON Semiconductor. This is a single-channel optocoupler which uses the low current provided by the output pin of the microcontroller (MCU) to activate its output stage. Besides an internal biasing LED, the MCU drives an additional external yellow LED, which signalizes that the MCU output is at a HIGH logic level. This led is labeled as ON, and it is used to indicate the state of the optocoupler output stage (conductive or non-conductive). The host MCU uses the CS pin of the mikroBUS™ to drive the input stage of the LTV-817S optocoupler. The working principle of an optocoupler is quite simple: A photo-emitting element - usually an IR LED - is integrated on a die along with the photosensitive element, usually a photosensitive transistor. The LED and the photosensitive transistor are isolated galvanically, but not optically: when the internal LED is powered, it emits light, which biases the base of the photosensitive transistor at the output stage, allowing the current to flow through it. In practice, an optocoupler may be equipped with additional elements such as Schmitt triggers, photo-sensitive Darlington pairs, various configurations of MOSFETs, and more. The output stage of the

optocoupler is used to drive the gate terminal of the FDD10AN06A0, an external power MOSFET, manufactured using the PowerTrench® technology, by ON Semiconductor. This MOSFET allows much more current to flow through the connected load, due to its extremely low ON resistance of about 10 mΩ, typically (10V). This MOSFET is designed to be used in switching circuits and for DC/DC converters, providing a high efficiency for these applications. As such, it has a very low capacitance on its gate terminal, allowing it to be driven with reasonably high-frequency PWM signals. The output stage of the LTV-817S optocoupler is connected to the VIN terminal of the external power supply connector, labeled as POWER. When the output stage of the optocoupler is closed (CS pin of the mikroBUS™ is at a HIGH logic level), it will connect the gate of the power MOSFET to the VIN voltage, thus enabling the power MOSFET. When the output stage of the optocoupler is opened (CS pin is at a LOW logic level), the gate of the MOSFET will be pulled down to the GND, by a 10K resistor, disabling the MOSFET. While enabled, the power MOSFET will be able to conduct the current through an external load, connected to the LOAD terminal. The output stage of the optocoupler also

has a green LED indicator labeled as OUT, which indicates that there is a valid voltage level across the POWER terminal. An undervoltage circuit on the VIN terminal prevents the voltage of the external power supply to drop under 10V. Ideally, the power supply voltage should stay above 12V. It is important for the voltage of the power supply to stay above 10V, since in that case, the ON resistance of the MOSFET is about 10 mΩ, ensuring that no significant heat dissipation will occur as a result of high current through the load. As the voltage of the externally connected power supply drops, it may cause the ON resistance of the power MOSFET to rise enough even before activating the undervoltage circuit (depending on the current through the load), resulting in its damaging. Therefore, the voltage of the external power supply must stay above 10V for this Click board™ to work reliably. The undervoltage protection feature can be useful to switch off the load in the case when the short-circuit condition occurs: the voltage of the power supply during short circuit event may drop, resulting the undervoltage circuit to be activated. However, if a reasonably strong power supply is used, the short-circuit current may be enough to destroy the power MOSFET or the input terminals.

Features overview

Development board

Curiosity PIC32 MZ EF development board is a fully integrated 32-bit development platform featuring the high-performance PIC32MZ EF Series (PIC32MZ2048EFM) that has a 2MB Flash, 512KB RAM, integrated FPU, Crypto accelerator, and excellent connectivity options. It includes an integrated programmer and debugger, requiring no additional hardware. Users can expand

functionality through MIKROE mikroBUS™ Click™ adapter boards, add Ethernet connectivity with the Microchip PHY daughter board, add WiFi connectivity capability using the Microchip expansions boards, and add audio input and output capability with Microchip audio daughter boards. These boards are fully integrated into PIC32’s powerful software framework, MPLAB Harmony,

which provides a flexible and modular interface to application development a rich set of inter-operable software stacks (TCP-IP, USB), and easy-to-use features. The Curiosity PIC32 MZ EF development board offers expansion capabilities making it an excellent choice for a rapid prototyping board in Connectivity, IOT, and general-purpose applications.

Microcontroller Overview

MCU Card / MCU

Architecture

PIC32

MCU Memory (KB)

2048

Silicon Vendor

Microchip

Pin count

100

RAM (Bytes)

524288

Used MCU Pins

mikroBUS™ mapper

RST

Optocoupler Input

RPD4

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

PWM

INT

SCL

SDA

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

Curiosity PIC32MZ EF front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Curiosity PIC32 MZ EF as your development board.

GNSS2 Click front image hardware assembly

GNSS2 Click complete accessories setup image hardware assembly

Curiosity PIC32 MZ EF MB 1 Access - upright/background hardware assembly

Curiosity PIC32 MZ EF MCU Step hardware assembly

Necto No Display image step 8 hardware assembly

Debug Image Necto Step hardware assembly

Track your results in real time

Application Output

1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support

Library Description

This library contains API for OPTO 4 Click driver.

Key functions:

opto4_output_enable - Function for output enable or disable

Open Source

Code example

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.

/*!
 * \file 
 * \brief OPTO 4 Click example
 * 
 * # Description
 * This click sets power on switch enabled and disabled.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initialization driver init.
 * 
 * ## Application Task  
 * The Output voltage enable and disable every 3 sec.
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "opto4.h"

// ------------------------------------------------------------------ VARIABLES

static opto4_t opto4;
static log_t logger;

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init ( void )
{
    log_cfg_t log_cfg;
    opto4_cfg_t cfg;

    /** 
     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
     */
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info(&logger, "---- Application Init ----");

    //  Click initialization.

    opto4_cfg_setup( &cfg );
    OPTO4_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    opto4_init( &opto4, &cfg );
}

void application_task ( )
{
    opto4_output_enable( &opto4, OPTO4_OUTPUT_ENABLE );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    opto4_output_enable( &opto4, OPTO4_OUTPUT_DISABLE );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}


// ------------------------------------------------------------------------ END