mikroElektronika BUCK click User manual

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
A1
Selects resistor
Switching frequency [MHz]
0
0
R7 = 130k
0.4
0
1
R8 = 32.4k
1.2
1
0
R9 = 54.9k
0.8
1
1
R10 = 21.5k
1.6
Specifications
Type
Buck
Applications
Automotive battery regulation, portable devices, industrial
supplies, etc.
On-board
modules
LT3976 step-down switching regulator, MAX4634 4-channel CMOS
analog multiplexer
Key Features
Thermal shutdown protection, output voltage can be set to 3.3V
or 5V, 4 possible switching frequencies
Interface
GPIO
Input Voltage
3.3V or 5V

Click board size
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
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
Designator
Name
Default
Position
Default
Option
Description
JP1
VOUT SEL
Right
3V3
Output Voltage Selection
3V3/5V, left position 5V, right
position 3V3.
JP2
VCC SEL
Left
3V3
Power Supply Voltage Selection
toward host MCU 3V3/5V; left
position 3V3, right position 5V