BUCK Click

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 from Analog Devices, 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.

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:

Specifications

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	Notes
	NC	1	AN	PWM	16	A1	Multiplexer A1 pin
Multiplexer A0 pin	A0	2	RST	INT	15	PG	Open drain output of an internal comparator
Enable IC	EN	3	CS	TX	14	NC
	NC	4	SCK	RX	13	NC
	NC	5	MISO	SCL	12	NC
	NC	6	MOSI	SDA	11	NC
Power supply	+3.3V	7	3.3V	5V	10	+5V	Power supply
Ground	GND	8	GND	GND	9	GND	Ground

Jumpers and settings

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 void systemInit()
02 {
03     UART1_Init(9600);
04 }
05 
06 void Buck_Init()
07 {
08     GPIO_Digital_Output( &GPIOC_BASE, _GPIO_PINMASK_2 );
09     GPIO_Digital_Output( &GPIOD_BASE, _GPIO_PINMASK_13 );
10     GPIO_Digital_Output( &GPIOA_BASE, _GPIO_PINMASK_0 );
11     GPIO_Digital_Input ( &GPIOD_BASE, _GPIO_PINMASK_10 );
12     BUCK_ENABLE_PIN = 1;
13     MUX_A0_PIN = 0;
14     MUX_A1_PIN = 0;   
15 }
16 
17 void Buck_Task()
18 {
19     if (PG_PIN == 1)
20     {
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 }