HOW DOES IT WORK?

Step Down 7 is based on the MAX17624, a synchronous step-down converter with integrated MOSFETs from Analog Devices. The converter uses soft start ramp technology, allowing a smooth output voltage increase. The output voltage is monitored through a resistor divider as feedback. On this Click board™, the resistor divider consists of a resistor, and the MCP4661T, an 8-bit dual digital POT with volatile memory from Microchip. This 50K digital potentiometer has a resistor ladder with ends connected to the analog switches and terminals A and B. The 256 resistors give 257 wiper positions. The potentiometer features high-speed read/write to the wiper and increment/decrement of wiper serial protocols.

The MAX17624 has two selectable modes of operation, the PWM and the PFM modes. The PWM mode is used in fixed-frequency operations with a fixed 4MHz switching frequency. This mode allows the device's output current to go negative and is useful in frequency-sensitive applications as it provides fixed switching frequency operations at all loads. The PWM mode gives lower efficiency at light loads compared to a PFM mode of operation. The PFM mode disables the negative output current from the device, and skips pulses at light loads for better efficiency. Another feature of the step-down converter is Power Good, which indicates the output voltage status.

Step Down 7 Click uses I/O pins to communicate with the host MCU. To change to the desired mode, you can set a logic state of the MD pin LOW for the PWM mode of operation; otherwise, the PFM mode is selected. Power Good output can be monitored over the PG pin. With the enabled EN pin, the MAX17624 will first go into soft start mode and, after 1ms, will smoothly increase the voltage. The feedback is provided over the resistor divider and the digital potentiometer, which uses a standard 2-Wire I2C interface to communicate with the host MCU, supporting frequencies of 100KHz, 400KHz, and 3.4MHz. The I2C address can be selected over the combination of the three jumpers, with all of them set to 0 by default.

This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

SPECIFICATIONS