Click here for production status of specific part numbers. Evaluates: MAXM17903 1.5V MAXM17903 1.5V Output Output-Voltage Application Evaluation Kit General Description Quick Start The MAXM17903 1.5V output evaluation kit (EV kit) Recommended Equipment provides a proven design to evaluate the MAXM17903 One 4.5V to 21.5V DC, 300mA power supply high-voltage, high-efficiency, synchronous step-down 0.5W resistive load with 300mA sink capacity DC-DC module. The EV kit is programmed to deliver 1.5V output for loads up to 300mA. The EV kit features Four digital multimeters (DMM) an adjustable input undervoltage lockout, selectable MAXM17903EVKIT mode, and open-drain RESET signal. The MAXM17903 data sheet provides a complete description of the module Equipment Setup and Test Procedure that should be read in conjunction with this EV kit data The EV kit is fully assembled and tested. Follow the steps sheet prior to modifying the demo circuit. For full module below to verify the board operation. features, benefits and parameters, refer to the MAXM17903 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 21.5V. Then, disable the power supply. Highly Integrated Solution 2) Connect the positive terminal of the power supply to Wide 4.5V to 21.5V Input Range the VIN PCB pad and the negative terminal to the Programmed 1.5V 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 75.50% Efficiency negative terminal to the nearest GND PCB pad. (V = 12V, V = 1.5V at 100mA) IN OUT 3) Connect the DVM (DMM in voltage-measurement 500kHz 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 4.1ms Soft-Start Time 6) Enable the load. RESET Output, with Pullup Resistor to V CC 7) Verify that the DVM displays 1.5V. Overcurrent and Overtemperature Protection (OCP and OTP) Ordering Information appears at end of data sheet. Low-Profile, Surface-Mount Components Proven PCB Layout Fully Assembled and Tested Complies with CISPR22(EN55022) Class B Conducted and Radiated Emissions 319-100149 Rev 1 1/19Evaluates: MAXM17903 1.5V MAXM17903 1.5V Output Evaluation Kit Output-Voltage Application Electromagnetic Interference (EMI) Detailed Description Compliance to conducted emissions (CE) standards The MAXM17903 EV kit is designed to demonstrate requires an EMI filter at the input of a switching power con- salient features of MAXM17903 power module. The EV kit verter. The EMI filter attenuates high-frequency currents includes an EN/UVLO PCB pad, and jumper J1, to enable drawn by the switching power converter, and limits the the output at a desired input voltage. Jumper J2 allows noise injected back into the input power source. selection of either PWM or PFM mode of operation based on light-load performance requirements. An additional Use of EMI filter components as shown in Figure 1 in RESET pad is available for monitoring if the converter conjunction with the schematic results in lower con- output voltage is in regulation. ducted emissions below CISPR22 Class B limits. The MAXM17903 1.5V EV Kit PCB Layout Diagrams is also Output Capacitor Selection designed to limit radiated emissions from switching nodes X7R ceramic output capacitors are preferred due to their of the power converter resulting in radiated emissions stability over temperature in industrial applications. The below CISPR22 Class B limits. required output capacitor (C5) for 1.5V output is selected from Table 1 of the MAXM17903 data sheet as 22F/6.3V. Hot-Plug-In and Long Input Cables The MAXM17903 EV kit PCB provides an optional Adjusting Output Voltage electrolytic capacitor (C2, 4.7F/50V) to dampen input The MAXM17903 supports an adjustable output-voltage voltage peaks and oscillations that can arise during hot- range, from 0.9V to 5V, using a feedback resistive divider plug-in and/or due to long input cables. This capacitor from V to FB. Output voltage can be programmed OUT limits the peak voltage at the input of the MAXM17903 using the values given in Table 1 of the MAXM17903 data power module, when the EV kit is powered directly from a sheet. For 1.5V output, R3 is chosen as 49.9k, and R4 precharged capacitive source or an industrial backplane is chosen as 75k. PCB. Long input cables, between input power source and the EV kit circuit can cause input-voltage oscillations due Enable/Undervoltage-Lockout (EN/UVLO) to the inductance of the cables. The equivalent series Programming The MAXM17903 offers an adjustable input undervoltage- Table 1. UVLO Enable/Disable lockout feature. In this EV kit, for normal operation, leave Configuration (J1) jumper J1 open. When J1 is left open, the MAXM17903 is enabled when the input voltage rises above 4.5V. To MAXM17903 POSITION EN/UVLO PIN disable MAXM17903, install a jumper across pins 2-3 on OUTPUT J1. See Table 1 for J1 settings. A potential divider formed Connected to the Programmed to by R1 and R2 sets the input voltage (V ) at which the INU Not center node of resistor- startup at desired module is enabled. The value of resistor R1 is chosen Installed* divider R1 and R2. input-voltage level. to be 2.2M, and R2 is calculated using the following equation: Enabled if V is IN 1-2 Connected to V IN greater than V IN(MIN). R 1.215 1 R = 2 2-3 Connected to GND Disabled ( V 1.215 ) INU *Default position where R1 and R2 are in k, For MAXM17903 to turn on at 4.5V input, the Resistor R2 is calculated to be 825k. VIN EMI VIN L1 Input Capacitor Selection VIN EMI 82H The input capacitor serves to reduce the current peaks drawn from the input power supply and reduces switching C C C 7 8 9 frequency ripple at the input. The input capacitance must 0.1F 0.47F 1F be greater than or equal to the value given in Table 1 of MAXM17903 data sheet. Input capacitor C3 is chosen to be 1F/25V. Figure 1. EMI Filter Components Maxim Integrated 2 www.maximintegrated.com