19-5772; Rev 1; 1/12 MAX16955 Evaluation Kit Evaluates: MAX16955 General Description Features The MAX16955 evaluation kit (EV kit) is a fully assembled and tested PCB that contains all the components necessary to evaluate the performance of the MAX16955 synchronous PWM step-down controller. The device is available in a 16-pin TSSOP package and features an exposed pad for enhanced thermal dissipation. S 6V to 36V Input Range The EV kit requires a 6V to 36V power supply for normal operation. The EV kit output is configured to 5V and can deliver up to 5A output current. The EV kit can be easily reconfigured to operate the controller in continuous PWM mode, SKIP mode, or external synchronization operation. The controller switching frequency is set to 400kHz. The EV kit includes a jumper to enable the circuit and an LED to monitor the power-good output. S Power-Good LED Indicator S 5V at Up to 5A Output S 400kHz Switching Frequency S Selectable Forced Fixed-Frequency PWM Mode, SKIP Mode, or External Synchronization S Enable Input S Cycle-by-Cycle Current Limit and Thermal Protection S Proven PCB Layout S Fully Assembled and Tested Ordering Information appears at end of data sheet. Component List DESIGNATION QTY DESCRIPTION Red multipurpose test points C11 1 4.7FF Q10%, 50V X7R ceramic capacitor (1206) Murata GRM31CR71H475K 1 0.22FF Q10%, 50V X7R ceramic capacitor (0805) Murata GRM21BR71H224K C13 1 4.7FF Q10%, 50V X7R ceramic capacitor (1210) Murata GRM32ER71H475K 1 47FF Q20%, 50V electrolytic capacitor (D8) Panasonic EEE-FK1H470XP D1 1 60V, 3A Schottky diode (SMB) Diodes Inc. B360B-13-F D2 1 Red LED (0603) D3 0 Not installed, Schottky diode (3 SOT23) JU1 1 3-pin header JU2 1 2-pin header L1 1 5.5FH Q20%,10A inductor Wurth 744325550 N1 1 40V, 6A dual n-channel MOSFET (8 SO) Fairchild FDS8949 PGND (x5), SGND 6 Black multipurpose test points R2, R5, R6 0 Not installed, resistors (0603) R4 1 0.015I Q1%, 1/2W resistor (1206) IRC LRF1206LF-01-R015-F R7, R12 2 0I Q5% resistors (0603) R8 1 66.5kI Q1% resistor (0603) DESIGNATION QTY BIAS, EN, FSYNC, OUT (x2), SUP (x2) 7 C1 C2 C4 C5, C9 C6 C7 C8 C10 1 DESCRIPTION 0.1FF Q10%, 50V X7R ceramic capacitor (0603) Murata GRM188R71H104K 0 Not installed, ceramic capacitors (0603) 1 100FF Q20%, 6.3V X5R ceramic capacitor (1210) TDK C3325X5R0J107M 1 47FF Q20%, 6.3V X7R ceramic capacitor (1210) Murata GRM32ER70J476M 1 1FF Q10%, 16V X7R ceramic capacitor (0603) Murata GRM188R71C105K 1 6800pF Q10%, 50V X7R ceramic capacitor (0603) Murata GRM188R71H682K __________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. MAX16955 Evaluation Kit Evaluates: MAX16955 Component List (continued) DESIGNATION QTY R9 1 13kI Q1% resistor (0603) DESCRIPTION R10 1 10kI Q5% resistor (0603) R11 1 51.1kI Q1% resistor (0603) U1 1 Synchronous buck converter (16 TSSOP-EP) Maxim MAX16955AUE/V+ DESIGNATION QTY -- 2 Shunts DESCRIPTION -- 1 PCB: MAX16955 EVALUATION KIT Component Suppliers SUPPLIER PHONE WEBSITE Diodes Incorporated 805-446-4800 www.diodes.com Fairchild Semiconductor 888-522-5372 www.fairchildsemi.com IRC, Inc. 361-992-7900 www.irctt.com Murata Electronics North America, Inc. 770-436-1300 www.murata-northamerica.com Panasonic Corp. 800-344-2112 www.panasonic.com TDK Corp. 847-803-6100 www.component.tdk.com Wurth Electronik GmbH & Co. KG 201-785-8800 www.we-online.com Note: Indicate that you are using the MAX16955 when contacting these component suppliers. Quick Start Required Equipment * MAX16955 EV kit 7) Turn on the power supply and set to 12V with a 1A current limit. 8) Enable the 1A electronic load. 9) Verify that the red LED (D2) is off and the DVM at OUT measures 5V. * 12V, 1A power supply * An electronic load capable of sinking 1A (e.g.,HP6060B) * Two digital voltmeters (DVMs) Procedure The EV kit is fully assembled and tested. Follow the steps below to verify board operation: 1) Verify that a shunt is installed across pins 2-3 on jumper JU1. 2) Verify that a shunt is not installed across jumper JU2 (output enabled). 3) Connect the load across the OUT and PGND test points. 4) Connect the first DVM across the SUP and PGND test points. 5) Connect the second DVM across the OUT and PGND test points. 6) Connect the power supply's positive and ground terminals to the SUP and PGND test points, respectively. Detailed Description of Hardware The MAX16955 EV kit is a fully assembled and tested PCB that contains all the components necessary to evaluate the performance of the MAX16955 synchronous PWM step-down controller. The device is available in a 16-pin TSSOP package and features an exposed pad for thermal dissipation. The device has a 3.5V to 36V input voltage range. The EV kit circuit is designed to operate from a single DC power supply ranging from 6V to 36V. The EV kit is configured to output 5V and provides up to 5A load current at the OUT and PGND test points. The switching frequency is set to 400kHz using resistor R8. The peak inductor current is set to 5.3A using resistor R4. The EV kit can be configured to operate in forced fixed-frequency PWM mode, low-quiescent current SKIP mode, or external synchronization using jumper JU1. The EV kit features test points to evaluate the enable (EN) feature and to monitor the BIAS output voltage. A red LED (D2) is available to monitor the power-good (PGOOD) output signal. __________________________________________________________________ Maxim Integrated Products 2 MAX16955 Evaluation Kit Evaluates: MAX16955 Table 1. Jumper Descriptions (JU1, JU2) JUMPER JU1 SHUNT POSITION 1-2 Connects FSYNC to VBIAS to enable continuous PWM mode. 2-3* Connects FSYNC to AGND to enable SKIP mode under light-load conditions. When FSYNC is unconnected, or when a clock source is present, continuous PWM mode is enabled. SYNC can be used to synchronize with other supplies when a clock source is present. Open JU2 DESCRIPTION Closed Connects EN to AGND (shutdown). Open* Connects EN to VSUP through a pullup resistor (normal operation). *Default position. Modes of Operation (JU1) Jumper JU1 configures the EV kit for external synchronization, forced fixed-frequency PWM, or SKIP mode operation. Install a shunt across pins 1-2 on JU1 to operate the EV kit in forced fixed-frequency PWM mode. Place a shunt across pins 2-3 on JU1 to operate in SKIP mode. Remove the shunt on JU1 when synchronizing, using an external digital clock signal at the FSYNC and SGND test points. Refer to the Forced Fixed-Frequency PWM Mode and Light-Load Low-Quiescent Operating (SKIP) Mode sections in the MAX16955 IC data sheet for additional information. See Table 1 for JU1 configuration. For external synchronization, apply a digital signal at the FSYNC and SGND test points with a frequency between 220kHz and 1.1MHz. For proper frequency synchronization, FSYNC's input frequency must be at least 110% of the EV kit's programmed internal oscillator frequency. When FSYNC is driven with an external digital clock, the device synchronizes to the rising edge of the external clock. The digital square-wave clock source at FSYNC must provide the following signal qualities: * 0 to 0.4V logic-low * 1.4V to 5.5V logic-high resistor value to set the switching frequency between 220kHz and 1MHz. Refer to the Setting the Switching Frequency section in the MAX16955 IC data sheet for selecting R8 when reconfiguring the EV kit switching frequency. When reconfiguring the EV kit switching frequency, it is necessary to replace the compensation network components C9, C10, R9, and power components. Refer to the Design Procedure section in the MAX16955 IC data sheet for computing new compensation and power component values. Configuring the Output Voltage (OUT) The EV kit step-down controller's output voltage (OUT) is configured to 5V. OUT can be reconfigured between 1V and 10V by removing resistor R7 and inserting feedback resistors at the R5 and R6 (0603) PCB pads. To configure the EV kit's output voltage, refer to the Setting the Output Voltage section in the MAX16955 IC data sheet for instructions on selecting resistor values. Also refer to the Effective Input-Voltage Range and Output Capacitor sections in the MAX16955 IC data sheet. Refer to the Design Procedure section in the MAX16955 IC data sheet and modify the compensation network accordingly. Power-Good Indicator (D2) * 220kHz to 1.1MHz input frequency * 100ns minimum pulse width Enable Control (JU2) The EV kit output is enabled through pullup resistor R11 when the power source applied between the SUP and PGND test points is greater than 1.8V. To enable the EV kit output, remove the shunt on jumper JU2. To disable the EV kit output, install a shunt on JU2. See Table 2 for JU2 configuration. If the EN pin is toggled from low to high, the switching regulator shuts down and remains off until the output voltage decays to 1.25V. At that point the EV kit output turns on using the soft-start sequence. Switching Frequency The controller's approximate switching frequency is set to 400kHz by resistor R8. Replace resistor R8 with a new The EV kit provides a red LED power-good indicator (D2) to monitor undervoltage and overvoltage conditions at OUT. D2 illuminates when OUT falls below 90% (typ) or rises above 111% (typ) of its nominal regulated voltage. Peak Inductor Current Limit The device's current-limit circuit uses differential currentsense inputs (CS and OUT) to limit the peak inductor current. The EV kit peak inductor current is set to 5.3A using resistor R4. Use the following equation to calculate the resistance needed to reconfigure the inductor peak current limit: 80mV R4 = IILIM where R4 is in milliohms and IILIM is the peak inductor current in amps. __________________________________________________________________ Maxim Integrated Products 3 MAX16955 Evaluation Kit Evaluates: MAX16955 Figure 1. MAX16955 EV Kit Schematic __________________________________________________________________ Maxim Integrated Products 4 MAX16955 Evaluation Kit Evaluates: MAX16955 1.0" 1.0" Figure 2. MAX16955 EV Kit Component Placement Guide-- Component Side Figure 3. MAX16955 EV Kit PCB Layout--Component Side 1.0" Figure 4. MAX16955 EV Kit PCB Layout--VCC Layer 2 __________________________________________________________________ Maxim Integrated Products 5 MAX16955 Evaluation Kit Evaluates: MAX16955 1.0" Figure 5. MAX16955 EV Kit PCB Layout--PGND and SGND Layer 3 1.0" Figure 6. MAX16955 EV Kit PCB Layout--Solder Side 1.0" Figure 7. MAX16955 EV Kit Component Placement Guide-- Solder Side __________________________________________________________________ Maxim Integrated Products 6 MAX16955 Evaluation Kit Evaluates: MAX16955 Ordering Information PART TYPE MAX16955EVKIT# EV Kit #Denotes RoHS compliant. __________________________________________________________________ Maxim Integrated Products 7 MAX16955 Evaluation Kit Evaluates: MAX16955 Revision History REVISION NUMBER REVISION DATE 0 2/11 Initial release -- 1/12 Changed VOUT max from 12V to 10V in the Configuring the Output Voltage (OUT) section to match the IC data sheet 3 1 DESCRIPTION PAGES CHANGED Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 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