Step Up Click Board™

The Step Up Click Board™ carries the MCP1665, a high-voltage, 3.6A, integrated switch PFM/PWM boost regulator, available in a 2mm x 2mm VQFN® package, from Microchip. Boost click provides an adjustable output voltage through the onboard DAC that drives the FB pin of the MCP1665 to set desired output voltage. The input voltage can be in range from 2.9V to 5V V from an external DC source connected to VIN screw terminal. The output voltage can be set up to 32V.

How Does The Step Up Click Board™ Work?

The Step Up Click Board™ utilizes the MCP1665, a 500 kHz, compact, high-efficiency, fixed-frequency, nonsynchronous step-up DC-DC converter that integrates a 36V, 100 mΩ NMOS switch, from Microchip. This IC is targeted towards boosting the voltage from NiCd, NiMH, Li-Po/Li-Ion batteries and as such it has a great efficiency factor, that allows for prolonged battery life. The MCP1665 IC uses the fixed switching frequency of 500 kHz and has the overvoltage protection to ensure safe operation.

Thanks to the under-voltage lockout feature, the voltage step-up process starts with the input voltage as low as 2.7V. MCP1665 features an UVLO that prevents fault operation below 2.7V, which corresponds to the value of three discharged primary Ni-Cd cells. The device starts its normal operation at 2.85V (typical) input. For the optimal efficiency, the device should be powered with at least 2.85V at the input terminal. Output current depends on the input and desired output voltage. For example, when powered with 4V at the input, Step Up click will be able to deliver about 1A @ 12V to the connected load. As with the most step-up regulators, the input voltage should always be less than the voltage at the output to maintain the proper regulation. On the diagram below, the dependence of the maximum output current (Iout) on the input and typical output voltages is given.

The MCP1665 step-up regulator actively damps the oscillations typically found at the switch node of a boost converter. This removes the high-frequency radiated noise, ensuring low noise operation.

Besides the MCP1665, Step Up 2 click also contains the D/A converter (DAC) labelled as MCP4921, 12-Bit DACs with the SPI Interface by Microchip, which is used in feedback loop. The DACs is connected to the feedback loop of the boost converter and therefore, the DAC signal which commonly ranges from 0 to +VREF, influences the voltage on the feedback midpoint. That way, the output voltage can be set to a desired value, up to 30V. The mentioned DAC uses SPI communication so the SDI, SDO, SCK, and CS pin of the mikroBUS™ are used for communication with the main MCU.

The device also features the mode pin, labelled as MOD, which is constructed as the open-drain output, that is pulled HIGH by the onboard 10K resistor. This allows an easy interfacing with the MCU and a simple solution to have the control over the switching mode. When the MOD pin is set to logic high level, the device is switching in PFM for light load. The MOD pin is routed to the mikroBUS™ RST pin

Besides the mode pin, the EN pin used to enable the device is routed to the mikroBUS™ CS pin. When pulled LOW, this pin will engage the true disconnect of the output load option, resulting in very low quintessential currents, suitable for the battery-operated devices. This pin is also pulled HIGH by the onboard resistor.

SPECIFICATIONS

PINOUT DIAGRAM

This table shows how the pinout of the Step Up Click Board™ 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	EN	Enable Input
Mode input	MOD	2	RST	INT	15	NC
SPI Chip Select	CS	3	CS	RX	14	NC
SPI Clock	SCK	4	SCK	TX	13	NC
SPI Data Out	SDO	5	MISO	SCL	12	NC
SPI Data In	SDI	6	MOSI	SDA	11	NC
NC	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

ONBOARD SETTINGS AND INDICATORS