BUCK click
PID: MIKROE-1592
BUCK click
is a buck switching regulator that accepts a wide input voltage range of up to 40V
and steps it down to 3.3V or 5V. The click carries the LT3976 40V, 5A, 2MHz step-down
switching regulator with 3.3µA quiescent current. BUCK click communicates with the target
microcontroller over the following pins on the mikroBUS™ line: PWM, INT, RS, CS.
Note: When all the usual conditions and proper cooling are met BUCK click can supply up to 5A of load
current.
LT3976 regulator features
The LT3976 is an adjustable frequency monolithic buck switching regulator that accepts a wide
input
voltage range up to 40V.
Low quiescent current design consumes only 3.3µA of supply
current while regulating with no load. Low ripple Burst Mode operation maintains high
efficiency at low output currents while keeping the output ripple below 15mV in a typical
application.
The LT3976 can supply
up to 5A
of load current and has current limit foldback to limit power
dissipation during short-circuit. A low dropout voltage of 500mV is maintained when the input
voltage drops below the programmed output voltage, such as during automotive cold crank.
How the click works
There are two onboard screw terminals, one for connecting the external input supply, and the
other for the output. There is also a multiplexer which chooses the resistor used for setting the
switching frequency.
The multiplexer is used for selecting one of the four different resistors. Each of these resistors, if
selected, sets different switching frequency:
A0
0
0
1
1
0
1
0
1
A1
Selects resistor
R7 = 130k
R8 = 32.4k
R9 = 54.9k
R10 = 21.5k
0.4
1.2
0.8
1.6
Switching frequency [MHz]
Specifications
Type
Applications
On‐board
modules
Key Features
Interface
Input Voltage
Click board size
Buck
Automotive battery regulation, portable devices, industrial supplies, etc.
LT3976 step‐down switching regulator, MAX4634 4‐channel CMOS analog multiplexer
Thermal shutdown protection, output voltage can be set to 3.3V or 5V, 4 possible
switching frequencies
GPIO
3.3V or 5V
L (57.15 x 25.4 mm)
Pinout diagram
This table shows how the pinout on BUCK click corresponds to the pinout on the
mikroBUS™ socket (the latter shown in the two middle columns).
Notes
Pin
Pin
1
2
3
4
5
AN
PWM 16
15
14
13
12
A1
PG
NC
NC
NC
NC
+5V
GND
Notes
Multiplexer A1 pin
Open drain output of an
internal comparator
NC
Multiplexer A0 pin
A0
Enable IC
EN
NC
RST INT
CS
TX
SCK RX
MIS
SCL
O
NC
NC
6
MOS
SDA 11
I
3.3V 5V
10
Power supply
Ground
+3.3V
7
GND
8
Power supply
Ground
GND GND 9
Jumpers and settings
Designator Name
VOUT
SEL
Default
Position
Right
Default
Option
3V3
Description
Output Voltage Selection 3V3/5V, left position 5V, right
position 3V3.
Power Supply Voltage Selection toward host MCU
3V3/5V; left position 3V3, right position 5V
JP1
JP2
VCC SEL Left
3V3
Programming
Code examples for BUCK click, written for MikroElektronika hardware and compilers are
available on Libstock.
Code snippet
This code enables the buck regulator and detects if the voltage is within 8.4% of final regulation
voltage.
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
void
systemInit()
{
UART1_Init(9600);
}
void
Buck_Init()
{
GPIO_Digital_Output(
GPIO_Digital_Output(
GPIO_Digital_Output(
GPIO_Digital_Input
(
BUCK_ENABLE_PIN
=
1;
MUX_A0_PIN
=
0;
MUX_A1_PIN
=
0;
}
void
Buck_Task()
{
if
(PG_PIN
==
1)
{
&GPIOC_BASE,
&GPIOD_BASE,
&GPIOA_BASE,
&GPIOD_BASE,
_GPIO_PINMASK_2
);
_GPIO_PINMASK_13
);
_GPIO_PINMASK_0
);
_GPIO_PINMASK_10
);
21
UART1_Write_text("Vout
is within the final 8.4% of final
regulation voltage");
22
UART1_Write_Text(
"rn"
);
23
delay_ms(1000);
24
}
25
26
}
27
28
void
main()
29
{
30
systemInit();
31
Buck_Init();
32
33
while(
1
)
34
{
35
Buck_Task();
36
}
37
}
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