Buck 8 click
PID: MIKROE-2997
Weight: 30 g
Buck 8 click is a high efficiency, wide voltage range, and high current synchronous step
down (buck) DC-DC converter, featuring two enhanced modes that can be used to drive
lighter loads with increased efficiency. The output voltage can be adjusted by the multiturn trimmer potentiometer. Since the output voltage is set mechanically, it will retain
the set value, even after the restart. Very high efficiency results with the reduced power
dissipation, thus allowing reasonably high power to be delivered to the load, connected to
the output terminal. Internal feedback compensation across the whole voltage range allows
lower number of external components.
Equipped with a number of different protection features such as the overload protection,
thermal protection, soft startup, this step-down converter offers a very secure and
convenient way of reducing the input voltage to a level necessary for the operation of any
low voltage application. It provides a clean, low noise and reliable power source. It can be
used for different types of power supplies, regulation of the wall transformers output,
single board applications powered by high voltage, and for any application that requires
clean and efficient step-down voltage conversion.
How does it work?
Buck 8 click uses the MAX17536, a high-efficiency, synchronous step-down DC-DC
converter with internal compensation, from Maxim Integrated. The MAX17536 is an
advanced integrated step-down converter, which is able to deliver reasonably high current,
up to 4A. The input voltage can range between 5V and 45V. It should stay roughly about
10% above the desired output voltage. This means that the output voltage ranges from the
0.9V up to 0.9 x Vin, where Vin is the input voltage.
The output voltage can be adjusted by a precise multi-turn potentiometer. This
potentiometer allows adjustment of the output voltage level by changing the resistance
value of the voltage divider that feeds part of the output voltage back to the FB pin of the
MAX17536. Since the potentiometer is a mechanical component, it will allow the output
voltage to remain the same, even after the power cycle.
Although it can deliver up to 4A, the output current is limited by the maximum power
dissipation of the converter. Although the percentage of the power lost on dissipation
varies with both input voltage and output current, it can be assumed that this power loss is
roughly 10%. According to the datasheet, maximum advisable power dissipation is 2.67W.
To allow for some overhead, it is safe to assume that the maximum power dissipation is
2W. This means that the maximum output power is about 20W. Bearing this in mind, the
maximum advisable output current will depend on the output voltage, according to the
following equation:
Iout = P/Vout
This function represents the Safe Operating Area (SOA) and it is graphically illustrated on
the bottom side of the Click board™. It holds true for Vin = 45V and switching frequency of
450kHz.
The MAX17536 features a robust overload and short circuit protection. When the internally
set current limit of 6.5A is exceeded, the high side MOSFET is turned off and the hiccup
mode is triggered. This mode suspends the operation for 32,768 duty cycles after which the
soft start sequence is reattempted. If the fault condition is present at the startup and
the outputvoltage remains under 68% of the nominal value, the hiccup mode is also
activated.
The thermal protection ensures that the junction temperature of the IC stays below 165˚C.
When this temperature is exceeded, the device shuts down, allowing it to cool down. When
the junction temperature drops for about 10˚C, the device is restarted.
The condition of the output voltage can be monitored via the #RESET pin of the MAX17536.
This pin is an open drain output and it is pulled to a HIGH logic level by the onboard
resistor. It is routed to the RST pin of the mikroBUS™ and can be used as the power good
indication. When the output voltage drops below 92.2% of the nominal regulated output
voltage, this pin is driven to a LOW logic level. Thermal shutdown event is also reported by
the #RESET pin.
The soft start feature prevents the inrush current. This feature is determined by the soft
start capacitor. The soft start is set to about 18ms by the 100nF capacitor.
The SYNC/MODE pin is pulled to a high logic level, allowing the device to work in the DCM
light load mode, allowing more efficient operation when the light load is connected to the
output. By driving the MODE/SYNC pin to a LOW logic level, the device is forced into the
PWM mode, which allows the least noise and ripple on the output, but it is not that efficient
when working with light loads. The MODE/SYNC pin is routed to the PWM pin of the
mikroBUS™ and it is pulled to a HIGH logic level by the onboard pull-up resistor. The device
latches the state of this pin at the startup, and it ignores pin state changes after the startup
sequence is finished.
One of the distinctive features of this buck converter is the ability to synchronize the
switching clock frequency with an external clock signal. It is possible to synchronize the
switching frequency within a range of about 1.1to 1.4higher than the value set on the Buck
8 click, which is 450kHz. This feature is primarily used to synchronize switching
frequencies when more than one buck converter is used. When the valid synchronization
signal is applied to the MODE/SYNC pin, the device is going to switch to the PWM mode,
with the switching frequency synchronized with the input signal. In this case, after the
synchronization signal is disconnected, the device will remain working in the PWM mode.
The EN pin of the MAX17572 is routed to the CS pin of the mikroBUS™. This pin is used to
enable the buck converter when driven to a HIGH logic level, but it can also be used to set
the undervoltage lockout threshold. If the input voltage falls under this threshold, the
internal low drop output regulators (LDOs) will not power on the internal logic and the
buck converter will stay disabled.
The Buck 8 click features an SMD jumper, which is used to set the logical voltage levels for
the pins, allowing both 3.3V and 5V MCUs to be used with the Click board™. The board is
also equipped with the input and output screw terminals, which allow secure connection of
the input voltage source and the load.
Specifications
Type
Buck
Applications
Wall transformer voltage regulators, general purpose power supplies,
distributed supply regulators, and similar applications where a high
current buck converter with a wide input voltage range, is required.
On-board
modules
MAX17536, a high-efficiency, synchronous step-down DC-DC
converter with internal compensation, from Maxim Integrated
Key Features
Wide input voltage range, adjustable output voltage, overcurrent
protection, thermal protection, soft start, adjustable PWM switching
frequency, very high efficiency, low external components count, etc.
Interface
GPIO
Input
Voltage
3.3V,5V
Click board
size
L (57.15 x 25.4 mm)
Pinout diagram
This table shows how the pinout on Buck 8 click corresponds to the pinout on the
mikroBUS™ socket (the latter shown in the two middle columns).
Notes
Pin
Pin
Notes
MODE/SYNC
pin
NC
1
AN
PWM
16
SYN
Buck output fault
signal
RST
2
RST
INT
15
NC
Enable outout
voltage
EN
3
CS
RX
14
NC
NC
4
SCK
TX
13
NC
NC
5
MISO
SCL
12
NC
NC
6
MOSI
SDA
11
NC
+3.3V
7
3.3V
5V
10
+5V
Power supply
GND
8
GND
GND
9
GND
Ground
Power supply
Ground
Buck 8 click electrical specifications
Description
Min
Typ
Max
Unit
Input Voltage
5
-
45
V
Output voltage
3.5
-
40
V
Output current
-
-
4
A
Onboard settings and indicators
Label
Name
Default
LD1
PWR
-
JP1
VCC SEL
Left
Description
Power LED indicator
Logic level voltage selection: left position
3.3V, right position 5V
Software support
We provide the library for Buck 8 click on our LibStock page, as well as the demo
application (example), developed using MikroElektronika compilers and mikroSDK. The
provided click library is mikroSDK standard compliant. The demo application can run on all
the main MikroElektronika development boards.
Library Description
The library carries functions related to GPIO pins control of the Buck 8 click. PWM control
is not part of the library and should be initialized depending on the development system.
Key functions:
•
•
void buck8_setMode(uint8_t mode) - Set working mode.
void buck8_enable( uint8_t state ) - Returns the status of the Click board™.
Examples Description
The demo application is composed of three sections:
•
System Initialization - Initialization of the CS and RST pin as INPUT.
•
Application Initialization - Initialization Driver init and set PWM frequency on 450kHz (OPEN
mode).
•
Application Task - (code snippet) - Logs the message to USBUART if the voltage is greater than
the maximum setpoint value.
void applicationTask()
{
if( buck8_getState() && flag == 0)
{
mikrobus_logWrite("max range ",_LOG_LINE);
flag = 1;
}
else
{
flag = 0;
}
Delay_1sec();
}
The full application code and ready-to-use projects can be found on our LibStock page.
Other MikroElektronika libraries used in the example:
•
UART
Additional notes and information
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 by the mikroSDK - MikroElektronika Software Development
Kit. To ensure proper operation of mikroSDK compliant click board demo applications, the
mikroSDK should be downloaded from the LibStock and installed for the compiler you are
using.
For more information about mikroSDK, visit the official page.
Downloads
mikroBUS™ Standard specification
LibStock: mikroSDK
Libstock: Buck 8 click library
MAX17536 datasheet
Buck 8 click schematic
Buck 8 click: 2D and 3D files
https://www.mikroe.com/buck-8-click 5-11-18
