Click here for production status of specific part numbers. Evaluates: MAXM17904 3.3V MAXM17904 3.3V Output Output-Voltage Application Evaluation Kit General Description Quick Start The MAXM17904 3.3V output evaluation kit (EV kit) Recommended Equipment provides a proven design to evaluate the MAXM17904 One 4.5V to 24V DC, 300mA power supply high-voltage, high-efficiency, synchronous step-down 1W resistive load with 300mA sink capacity DC-DC module. The EV kit is programmed to deliver 3.3V output for loads up to 300mA. The EV kit features an Four digital multimeters (DMM) adjustable input undervoltage lockout, selectable mode, MAXM17904EVKIT and open-drain RESET signal. The MAXM17904 data sheet provides a complete description of the module that Equipment Setup and Test Procedure should be read in conjunction with this EV kit data sheet The EV kit is fully assembled and tested. Follow the steps prior to modifying the demo circuit. For full module fea- below to verify the board operation. tures, benefits and parameters, refer to the MAXM17904 Caution: Do not turn on power supply until all data sheet. connections are completed. 1) Set the power supply at a voltage between 4.5V and Features 24V. Then, disable the power supply. Highly Integrated Solution 2) Connect the positive terminal of the power supply to Wide 5.5V to 24V Input Range the VIN PCB pad and the negative terminal to the Fixed 3.3V Output, Delivers Up To 300mA nearest GND PCB pad. Connect the positive termi- Output Current nal of the 300mA load to the VOUT PCB pad and the High 85.57% Efficiency negative terminal to the nearest GND PCB pad. (V = 12V, V = 3.3V at 100mA) IN OUT 3) Connect the DVM (DMM in voltage-measurement 550kHz Switching Frequency mode) across the VOUT PCB pad and the nearest GND PCB pad. ENABLE/UVLO Input, Resistor-Programmable UVLO Threshold 4) Verify that shunt is not installed on jumper J1 (see Table 1 for details). PFM Feature for Better Light-Load Efficiency 5) Turn on the DC power supply. Fixed Internal 3.75ms Soft-Start Time 6) Enable the load. RESET Output, with Pullup Resistor to V CC 7) Verify that the DVM displays 3.3V. Overcurrent and Overtemperature Protection (OCP and OTP) Low-Profile, Surface-Mount Components Proven PCB Layout Ordering Information appears at end of data sheet. Fully Assembled and Tested Complies with CISPR22(EN55022) Class B Conducted and Radiated Emissions 319-100387 Rev 0 6/19Evaluates: MAXM17904 3.3V MAXM17904 3.3V Output Evaluation Kit Output-Voltage Application Input Capacitor Selection Detailed Description The input capacitor serves to reduce the current peaks The MAXM17904 EV kit is designed to demonstrate drawn from the input power supply and reduces switching salient features of MAXM17904 power module. The EV kit frequency ripple at the input. The input capacitance must includes an EN/UVLO PCB pad, and jumper J1, to enable be greater than or equal to the value given in Table 1 of the output at a desired input voltage. Jumper J2 allows MAXM17904 data sheet. Input capacitor C3 is chosen to selection of either PWM or PFM mode of operation based be 1F/50V. on light-load performance requirements. An additional RESET pad is available for monitoring if the converter Electro-Magnetic Interference (EMI) output voltage is in regulation. Compliance to conducted emissions (CE) standards Output Capacitor Selection requires an EMI filter at the input of a switching power converter. The EMI filter attenuates high-frequency cur- X7R ceramic output capacitors are preferred due to their rents drawn by the switching power converter, and limits stability over temperature in industrial applications. The the noise injected back into the input power source. required output capacitor (C5) for 3.3V output is selected from Table 1 of the MAXM17904 data sheet as 10F/6.3V. Use of EMI filter components as shown in Figure 1 in conjunction with the schematic results in lower con- Fixed Output Voltage ducted emissions, below CISPR22 Class B limits. The The MAXM17904 is a fixed 3.3V output module. Connect MAXM17904 EV kit PCB layout is also designed to limit FB of MAXM17904 directly to VOUT for feedback control. radiated emissions from switching nodes of the power converter, resulting in radiated emissions below CISPR22 Enable/Undervoltage-Lockout (EN/UVLO) Class B limits. Programming The MAXM17904 offers an adjustable input undervoltage- lockout feature. In this EV kit, for normal operation, leave jumper J1 open. When J1 is left open, the MAXM17904 is VIN EMI VIN enabled when the input voltage rises above 5.4V. To dis- able MAXM17904, install a jumper across pins 2-3 on J1. L1 VIN EMI See Table 1 for J1 settings. A potential divider formed by R1 and R2 sets the input voltage (V ) at which the mod- INU 82H C9 C8 ule is enabled. The value of resistor R1 is chosen to be C7 2.2M, and R2 is calculated using the following equation: 0.47F 1F 0.1F R 1.215 1 R = 2 ( V 1.215 ) INU where R1 and R2 are in k, Figure 1. EMI Filter Components For MAXM17904 to turn on at 5.4V input, the Resistor R2 is calculated to be 634k. Table 1. UVLO Enable/Disable Configuration (J1) POSITION EN/UVLO PIN MAXM17904 OUTPUT Connected to the center node of resistor-divider Programmed to startup at desired input-voltage Not Installed* R1 and R2. level. 1-2 Connected to V Enabled if V is greater than V IN IN IN(MIN). 2-3 Connected to GND Disabled *Default position Maxim Integrated 2 www.maximintegrated.com