Buck 12 Click

The MPQ8632 has a wide voltage input range, which is one of its key features. It uses Constant-On-Time (COT) control mode to provide fast transient response and ease loop stabilization. It also features a set of standard protection options, found on many similar devices: over-current protection, over-voltage protection and thermal shutdown, etc. The Click board™ can be used for a wide range of applications that require 3.3V, including field embedded applications, sensors, PLC modules, video surveillance systems, and similar applications that require step-down conversion to 3.3V.

How does it work?

Buck 12 click is equipped with the MPQ8632, a synchronous step-down converter, from Monolithic Power Systems (MPS). This is an advanced integrated step-down converter, which requires a minimum number of external components, readily available on the market. It utilizes a peak-current-mode control architecture, which along with the automatic switch-mode switching, ensures a very good efficiency. The MPQ8632 buck converter features over-current, under-voltage, and thermal protection, making Buck 12 click a robust and reliable power supply solution.

The output voltage is determined by the feedback voltage on the FB pin. The output voltage is set to 3.3V making it usable with most embedded applications, allowing them to be powered from the same source, like the rest of the application, which may use a higher voltage for its operation. This is a common-case scenario in various field applications where a relatively high voltage is required i.e. for servos, step motors, displays, etc.

When there is overload at the output, the low-side MOSFET will allow the inductor current to drop. It will remain open until the current through the inductor falls below the limit. If the FB voltage drops too much during the overload, the device enters the hiccup mode, in which the device disables the output power stage, discharges the soft-start capacitor and then automatically retries soft-start.

The MPQ8632 is able to automatically switch between different operating modes, depending on the current through the load. At very light loads, the device is operated in skip mode. In this mode HS-FET turns on for a fixed interval determined by the one-shot on-timer. When the HS-FET turns off, the LS-FET turns on until the inductor current reaches zero. The LS-FET driver turns into tri-state (high Z) whenever the inductor current reaches zero. This way, the device is in an idle state, while the light load consumes energy stored within the coil. This greatly improves the efficiency when a light load is used. This is also called discontinuous conduction mode (DCM).

When heavily loaded, The MPQ8632 is automatically switches to heavy load operation or continuous-conduction-mode (CCM). In this mode, when VFB is below VREF, HS-FET turns on for a fixed interval determined by the one- shot on-timer. When the HS-FET turns off, the LS-FET turns on until the next period. In CCM operation, the switching frequency is fairly constant and is also called PWM mode.

Packed in QFN casing (3X4mm), the MPQ8632 occupies a very small area on the PCB. Combined with the low count of external components it requires, the MPQ8632 leaves enough space for an additional IC to be used. This click uses the MCP3202, a Dual Channel 12-Bit A/D Converter which uses the SPI interface, from Microchip. It allows monitoring the input and output voltages over the SPI interface. This ADC is powered from the +5V mikroBUS™ power rail. The same voltage is used as a reference. The Click board™ itself requires an external power supply to be connected at the input terminal, labeled as VIN. The VOUT terminal provides the connected load with the regulated 3.3V voltage.

Specifications

Pinout diagram

This table shows how the pinout on Buck 12 click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
Enable input	EN	2	RST	INT	15	NC
Chip Enable	CS	3	CS	RX	14	NC
SPI Clock	SCK	4	SCK	TX	13	NC
SPI SDO	SDO	5	MISO	SCL	12	NC
SPI SDI	SDI	6	MOSI	SDA	11	NC
	NC	7	3.3V	5V	10	5V	Power supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

Buck 12 Click electrical specifications

Software Support

We provide a library for the Buck 12 click on our LibStock page, as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Library Description

The library initializes and defines the SPI bus driver. The library includes function for enable or disable buck device. The user also has the function for read voltage on the input and output terminal.

Key functions:

• void buck12_control(uint8_t ctrl) – Function for enable or disable device.
• float buck12_getVoltage(uint8_t selectVolt) – Function for get Voltage.

Examples description

The application is composed of three sections :

• System Initialization – Initializes SPI module and sets CS pin and RST pin as OUTPUT.
• Application Initialization – Initialization driver init and BUCK enabled.
• Application Task – Reads the voltage in [mV] at the input and output terminals. This data logs to the USBUART every 2 sec.

Note: Voltage on VIN terminal must be between 2.5V and 18V. When the BUCK is enabled – the voltage on the VOUT terminal is about 3.3V..

void applicationTask()
{
    char demoText[ 20 ];
    float Voltage;

    Voltage = buck12_getVoltage(_BUCK12_INPUT_VOLTAGE);
    
    FloatToStr(Voltage, demoText);
    mikrobus_logWrite("* VIN : ", _LOG_TEXT);
    mikrobus_logWrite(demoText, _LOG_TEXT);
    mikrobus_logWrite(" mV", _LOG_LINE);
    
    Voltage = buck12_getVoltage(_BUCK12_OUTPUT_VOLTAGE);

    FloatToStr(Voltage, demoText);
    mikrobus_logWrite("* VOUT : ", _LOG_TEXT);
    mikrobus_logWrite(demoText, _LOG_TEXT);
    mikrobus_logWrite(" mV", _LOG_LINE);
    
    mikrobus_logWrite("--------------------------", _LOG_LINE);
    Delay_ms( 2000 );
}

The full application code, and ready to use projects can be found on our LibStock page.

Other mikroE Libraries used in the example:

• SPI
• UART
• Conversions

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.