Evaluates: MAX17761 in MAX17761 5V Output 5V Output-Voltage Application Evaluation Kit General Description Quick Start The MAX17761 5V output EV kit is a proven design to Recommended Equipment evaluate the MAX17761 high-efficiency, high-voltage, MAX17761 5V output EV kit synchronous step-down DC-DC converter in a TDFN 6.5V to 76V, 2A DC input power supply package. The EV kit generates 5V at load currents up to 1A from a 6.5V to 76V input supply. The EV kit features Load capable of sinking 1A a 400kHz switching frequency for optimum efficiency and Digital voltmeter (DVM) component size. The EV kit features adjustable input undervoltage lockout, adjustable soft-start, adjustable Procedure switching frequency, adjustable current limit, open-drain The EV kit is fully assembled and tested. Follow the steps RESET signal and external frequency synchronization. below to verify board operation. Caution: Do not turn on power supply until all connections are completed. Features 1) Set the power supply at a voltage between 6.5V and Operates from a 6.5V to 76V Input Supply 76V. Disable the power supply. 5V Output Voltage 2) Connect the positive terminal of the power supply to Up to 1A Output Current the VIN PCB pad and the negative terminal to the nearest PGND PCB pad. Connect the positive terminal 400kHz Switching Frequency of the 1A load to the VOUT PCB pad and the negative Enable/UVLO Input, Resistor-Programmable UVLO terminal to the nearest PGND PCB pad. Threshold 3) Connect the DVM across the VOUT PCB pad and Adjustable Soft-Start Time the nearest PGND PCB pad. MODE/ILIM Pin to Select Among PWM or PFM 4) Verify that shunts are installed across pins 1-2 on Modes and 1.6A or 1.14A current limits jumper JU1, JU2, and JU3 (see Table 3 for details). Auxiliary Bootstrap LDO to improve efficiency 5) Turn on the DC power supply. Open-Drain RESET Output 6) Enable the load. External Frequency Synchronization 7) Verify that the DVM displays 5V. Overcurrent and Overtemperature Protection Proven PCB Layout Fully Assembled and Tested Ordering Information appears at end of data sheet. 319-100053 Rev 1 2/18Evaluates: MAX17761 in MAX17761 5V Output Evaluation Kit 5V Output-Voltage Application Current Limit and Mode of Detailed Description Operation Selection The MAX17761 5V Output EV kit provides a proven design to evaluate the MAX17761 high-efficiency, high- The following table lists the values of the resistor R5 to voltage, synchronous step-down DC-DC converter. The program PWM or PFM modes of operation and 1.6A or EV kit generates 5V at load currents up to 1A from a 6.5V 1.14A peak current limits. to 76V input supply. The EV kit features a 400kHz switching Table 1. R Resistor vs. Modes of ILIM frequency for optimum efficiency and component size. Operation and Peak Current Limit The EV kit includes an EN/UVLO PCB pad and JU1 to R5 MODE OF PEAK CURRENT enable the output at a desired input voltage. The RT/SYNC (k) OPERATION LIMIT (A) PCB pad and JU3 allow an external clock to synchronize the device. An additional RESET PCB pad is available for OPEN PFM 1.6 monitoring when the converter output is in regulation. 422 PFM 1.14 Soft-Start Input (SS) 243 PWM 1.6 The device implements adjustable soft-start operation to 121 PWM 1.14 reduce inrush current. A capacitor connected from the SS The mode of operation cannot be changed on-the-fly after pin to SGND programs the soft-start time for the corre- power-up. sponding output voltage. The selected output capacitance Switching Frequency Selection and (C ) and the output voltage (V ) determine the mini- SEL OUT External Frequency synchronization mum required soft-start capacitor as follows: -6 The RT/SYNC pin programs the switching frequency of C 30 x 10 x C x V SS SEL OUT the converter. The resistor R7 sets the switching frequency The soft-start time (t ) is related to the capacitor con- SS of the part at any one of four discrete frequencies nected at SS (C ) by the following equation: SS 200kHz, 300kHz, 400kHz, and 600kHz. The following table gives the resistor values. C SS t = SS The internal oscillator of the MAX17761 can be synchro- 6 6.25 10 Table 2. Switching Frequency For example, to program a 5.3ms soft-start time, a 33nF vs. RT Resistor capacitor should be connected from the SS pin to SGND. SWITCHING FREQUENCY (kHz) R7 (k) The minimum possible soft-start time is 5ms. 200 210 Regulator Enable/Undervoltage-Lockout Level 300 140 (EN/UVLO) 400 105 The device offers an adjustable input undervoltage-lock- 600 69.8 out level. For always on operation, no shunt should be installed across JU1. To disable the output, install a shunt across pins 2-3 on JU1 and the EN/UVLO pin is pulled to nized to an external clock signal on the RT/SYNC pin. A GND. See Table 3 for JU1 settings. shunt should be placed across the jumper JU3 for this purpose. The external synchronization clock frequency Set the voltage at which each converter turns on with a must be between 1.15 x f and 1.4 x f , where f is SW SW SW resistive voltage-divider connected from VIN to SGND. the frequency programmed by R7. Connect the center node of the divider to EN/UVLO pin. Table 3. Regulator Enable (EN/UVLO) Choose R1 as follows: Description (JU1) R1 (110000 x V ) INU SHUNT Where V is the input voltage at which the MAX17761 INU EN/UVLO PIN MAX17761 OUTPUT POSITION is required to turn ON and R1 is in . Calculate the value Not Installed Floating Always ON of R2 as follows: Enabled, UVLO level set 1.215 R1 Connected to the center node R2 = 1-2 through the R1 and R2 of resistor-divider R1 and R2 (V 1.215+ (2.5AR1)) INU resistors 2-3 Connected to SGND Disabled Maxim Integrated 2 www.maximintegrated.com