Buck-Boost Click Board™

How Does The Buck-Boost Click Board™ Work?

The Buck-Boost Click Board™ is based on the LTC3129-1, a 1.3μA quiescent current, monolithic, current mode, buck-boost DC/DC converter that can operate over a wide input voltage range of 1.92V to 15V and provide up to 200mA to the load from Analog Devices. The LTC3129-1 is characterized by its very low noise and low ripple level at the output, as well as very high regulating efficiency and low quiescent current. Eight fixed, user-programmable output voltages can be selected using the three digital programming pins routed to the INT, AN, and CS pin of the mikroBUS™ socket. A proprietary switch control algorithm allows the Buck-Boost converter to maintain output voltage regulation with input voltages that are above, below, or equal to the output voltage. Transitions between the step-up or step-down operating modes are seamless and free of transients and sub-harmonic switching, making this product ideal for noise-sensitive applications.

The Buck-Boost Click Board™ possesses two different modes of operation - PWM and Burst Mode, depending on the nature of the application. The PWM mode can be selected by setting the PWM pin of the mikroBUS™ socket to a logic high level and is suitable for working with higher loads connected to the converter output and when the extremely low output noise is required. When the PWM mode is selected, LTC3129-1 has a fixed nominal switching frequency of 1.2MHz using an internally compensated average current mode control loop. In this mode, the ripple and the noise level of the output voltage are minimal.

For high-efficiency operation at light loads, automatic Burst Mode operation can be selected, reducing the quiescent current down to 1.3µA. Burst mode can be chosen if the PWM pin is set to a logic low level. If the connected load is light enough, the converter will remain working in Burst mode, running only when necessary to maintain voltage regulation. Otherwise, the PWM mode will be automatically engaged, providing enough current for the connected load.

The Buck-Boost Click Board™ completely powers itself from the VIN external power supply terminal. Once the power is applied to the VIN terminal, the circuit also has to be enabled by setting the RUN pin routed to the RST pin of the mikroBUS™ socket to a high logic level. This will power up the converter, which will be indicated by the PWR LED indicator. It also includes additional features such as a power-good output with a Power Good LED indicator labelled as PGOOD that pulls to the ground when FB drops too far below its regulated voltage. This pin also can sink up to the absolute maximum rating of 15mA when set low.

VOLTAGE SELECTION PINS SETTINGS

SPECIFICATIONS

PINOUT DIAGRAM

This table shows how the pinout of the Buck-Boost Click Board™ corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
Output voltage select pin	VS2	1	AN	PWM	16	PWM	Mode select pin
Enable pin	RUN	2	RST	INT	15	VS1	Output voltage select pin
Output voltage select pin	VS3	3	CS	RX	14	NC
NC	4	SCK	TX	13	NC
NC	5	MISO	SCL	12	NC
NC	6	MOSI	SDA	11	NC
NC	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

ONBOARD SETTINGS AND INDICATORS

BUCK-BOOST CLICK ELECTRICAL SPECIFICATIONS