MAX20050EVKIT# Analog Devices

Evaluates: MAX20050/MAX20052 MAX20050 Evaluation Kit General Description Features and Benefits The MAX20050 evaluation kit (EV kit) demonstrates the 4.5V to 65V Input Voltage MAX20050 and MAX20052, 1.5A synchronous buck LED Drives 1 to 16 LEDs drivers with integrated MOSFETs. 0A to 1.5A LED Current The EV kit operates from a DC supply voltage from Demonstrates Undervoltage-Lockout and Output 4.5V to 65V and the switching frequency is fixed at Short Protection 400kHz. Spread-spectrum mode (SSM) is enabled for Demonstrates Current-Limit and Thermal-Shutdown EMI improvement. The EV kit demonstrates both analog and pulse-width modulation (PWM) dimming. The EV kit Feature also demonstrates short LED, open LED, and overtem- Demonstrates 5V, 10mA LDO Output Capability perature fault protection. Proven PCB Layout and Thermal Design The EV kit comes with a MAX20052ACTV IC, which can Fully Assembled and Tested be installed to evaluate the 2.1MHz switching frequency device. See the Evaluating the MAX20052 section for more information. Ordering Information appears at end of data sheet. MAX20050 EV Kit Photo 19-7511 Rev 0 2/15Evaluates: MAX20050/MAX20052 MAX20050 Evaluation Kit Quick Start Detailed Description of Hardware The MAX20050 EV kit demonstrates the MAX20050 1.5A Required Equipment synchronous buck LED driver with integrated MOSFETs. MAX20050 EV kit The device consists of a fully synchronous step-down 5V to 65V, 4A DC power supply converter with integrated MOSFETs. The device is capable of driving a series string of LEDs at up to 1.5A, Two digital voltmeters (DVMs) with a minimum number of external components. The One series-connected HB LED string rated to no device is a fixed-frequency average current-mode step- less than 2A down LED driver. The device uses high-side current Current probe to measure the HB LED current regulation, meaning a current-sense resistor is placed on Small flat-blade screwdriver to turn the potentiometer the high side of the LED string, and the voltage across wiper adjustment pin the current-sense resistor is sensed and used to regulate the LED current. The device offers both analog and PWM Procedure dimming. The device features internal error amplifier The EV kit is fully assembled and tested. Follow the steps compensation. Refer to the MAX20050MAX20053 IC below to verify board operation: data sheet for recommended inductor values to ensure stable operation. 1) Connect the HB LED string anode to the LED+ PCB pad and the cathode to the PGND PCB pad. Analog Dimming 2) Connect the first DVM across the LED+ and PGND The EV kit demonstrates the analog dimming feature of PCB pads. the device. R6 and R7 form a resistor-divider between 3) Connect the second DVM across the REFI test point V and AGND. R6 is a 10k resistor and R7 is a 10k CC and the AGND test point. potentiometer, with the wiper shorted to the high side of 4) Connect the power supply to the VIN PCB pad and the potentiometer. Using a flat-blade screwdriver, turn the the power-supply ground to the PGND PCB pad. wiper adjustment pin clockwise to increase the voltage on 5) Clip the current probe across the wire connecting the the REFI input. Turn the wiper adjustment pin counter- HB LED string to the EV kit clockwise to decrease the voltage on the REFI input. 6) Turn on the power supply and set it to a voltage The REFI input allows for analog dimming of the HB LED greater than the maximum HB LED string voltage, string. A REFI input voltage of 0.2V or less turns off the but less than the 65V maximum input voltage. LED driver. A REFI input voltage between 0.2V and 1.2V 7) Use the screwdriver to turn the potentiometer until provides linear dimming of the HB LED string. A REFI input the second DVM reads 1.14V. voltage greater than 1.2V sets the HB LED string current 8) Measure the HB LED current using the current probe to maximum current (based on the current-sense resistor). and verify that the current is 1.5A. 9) Verify that the first DVM shows the expected LED Alternatively, the analog dimming input can be set with string voltage. a power supply. Remove R12 and connect the power 10) Use the screwdriver to turn the potentiometer until supply directly to the REFI test point to perform analog the second DVM reads 0.67V. dimming with a power supply. Be careful not to violate 11) Measure the HB LED current using the current probe the absolute maximum voltage rating of V + 0.3V CC and verify that the current is 0.75A. (refer to the Absolute Maximum Ratings section in the MAX20050MAX20053 IC data sheet). Maxim Integrated 2 www.maximintegrated.com