Evaluates: MAX17575 in 3.3V MAX17575 3.3V Output Output-Voltage Application Evaluation Kit General Description Quick Start The MAX17575 3.3V output evaluation kit (EV kit) Recommended Equipment provides a proven design to evaluate the MAX17575 MAX17575 3.3V output EV kit high-voltage, high-efficiency, synchronous step-down 4.5V to 60V, 2A DC input power supply DC-DC converter. The EV kit is preset for 3.3V output at load currents up to 1.5A and features a 500kHz switching Load capable of sinking 1.5A frequency for optimum efficiency and component size. Digital voltmeter (DVM) The EV kit features adjustable input undervoltage lockout, adjustable soft-start, open-drain active-low RESET signal, Procedure and external frequency synchronization. The EV kit is fully assembled and tested. Follow the steps below to verify the board operation. Caution: Do not turn Features on power supply until all connections are completed. Operates from a 4.5V to 60V Input Supply 1) Set the power supply at a voltage between 4.5V and 3.3V Output Voltage 60V. Disable the power supply. 2) Connect the positive terminal of the power supply Up to 1.5A Output Current to the V PCB pad and the negative terminal to the IN 500kHz Switching Frequency nearest PGND PCB pad. Connect the positive terminal Enable/UVLO Input, Resistor-Programmable UVLO of the 1.5A load to the V PCB pad and the negative OUT Threshold terminal to the nearest PGND PCB pad. 3) Connect the DVM across the V PCB pad and OUT Adjustable Soft-Start Time the nearest PGND PCB pad. Open-Drain RESET Output 4) Verify that shunts are installed across pins 1-2 on External Frequency Synchronization jumper JU1 (see Table 1 for details). 5) Turn on the DC power supply. Overcurrent and Overtemperature Protection 6) Enable the load. Proven PCB Layout 7) Verify that the DVM displays 3.3V Fully Assembled and Tested Ordering Information appears at end of data sheet. 19-8767 Rev 1 6/17Evaluates: MAX17575 in 3.3V MAX17575 3.3V Output Evaluation Kit Output-Voltage Application EN/UVLO. Choose R1 to be 3.3M and then calculate Detailed Description of Hardware R2 as follows: The MAX17575 3.3V output EV kit provides a proven design to evaluate the MAX17575 high-voltage, high- 1.215 R1 R2 = efficiency, synchronous step-down DC-DC converter. The (V 1.215) INU EV kit is preset for 3.3V output from 4.5V to 60V input at load currents up to 1.5A and features a 500kHz switching where V is the voltage at which the device is required INU frequency for optimum efficiency and component size. to turn on. Ensure that V is higher than 0.8 x V . INU OUT The EV kit includes an EN/UVLO PCB pad and jumper If the EN/UVLO pin is driven from an external signal source, JU1 to enable the output at a desired input voltage. An a series resistance of minimum 1k is recommended to additional RESET PCB pad is available for monitoring be placed between the signal source output and the EN/ whether the converter output is in regulation. UVLO pin, to reduce voltage ringing on the line. Soft-Start capacitor selection Adjusting Output Voltage The device implements adjustable soft-start operation to Set the output voltage with a resistive voltage-divider reduce inrush current. A capacitor connected from the SS connected from the positive terminal of the output capaci- pin to GND programs the soft-start time. The selected tor (V ) to SGND (Figure 2). Connect the center node OUT output capacitance (C ) and the output voltage (V ) SEL OUT of the divider to the FB pin. Use the following procedure to determine the minimum required soft-start capacitor choose the resistive voltage-divider values: as follows: Calculate resistor R3 from the output to the FB pin as 6 C 56 10 C V follows: SS SEL OUT 1850 The soft-start time (t ) is related to the capacitor con- SS R3 = nected at SS (C ) by the following equation: C SS OUT SEL C Where C (in F) is the actual derated value of SS OUT SEL t = SS 6 the output capacitance used and R3 is in k. The minimum 5.55 10 allowable value of R3 is (5.6 x V ), where R3 is in k. OUT For example, to program a 2ms soft-start time, a 12nF If the value of R3 calculated using the above equation. capacitor should be connected from the SS pin to GND. is less than (5.6 x V ), increase the value of R3 to at OUT least (5.6 x V ). OUT Setting the Undervoltage-Lockout Level The device offers an adjustable input undervoltage-lockout R3 0.9 R4 = level. Set the voltage at which the device turns on with (V 0.9) OUT a resistive voltage-divider connected from V to SGND IN (Figure 1). Connect the center node of the divider to R4 is in k. Table 1. Regulator Enable (EN/UVLO) Description (JU1) SHUNT POSITION EN/UVLO PIN MAX17575 OUTPUT 1-2* Connected to VIN Enabled Connected to the center node of resistor-divider Enabled, UVLO level set through the Not installed R1 and R2 R1 and R2 resistors 2-3 Connected to SGND Disabled Maxim Integrated 2 www.maximintegrated.com