MAX20078EVKIT#

Evaluates: MAX20078 MAX20078 Evaluation Kit General Description The MAX20078 evaluation kit (EV kit) provides a proven design to evaluate the MAX20078 synchronous buck controller for high-power, high-brightness (HB) LED drivers. The EV kit is set up as a buck LED driver and operates from a 4.5V to 65V DC supply voltage. The EV kit is configured to deliver up to 2A to one string of LEDs. The total voltage of the string can vary from 3V to 55V. The anode of the LED string should be connected to the LED+ terminal and the cathode of the LED string connected to PGND. Procedure The EV kit is fully assembled and tested. Follow the steps below to verify board operation. Caution: Do not turn on the power supply until all connections are complete. 1) Verify that all jumpers (J1, JU1–JU4) are in their default positions, as shown in Table 1. 2) Connect the HB LED string anode to the LED+ PCB pad and the cathode to the PGND PCB pad. 3) Connect DVM1 across the LED+ and PGND PCB pads. 4) Connect DVM2 across the REFI and AGND test points. 5) Connect the power supply to the VIN PCB pad and the power supply’s ground to the PGND PCB pad. ● 0A to 2A LED Current 6) ● Demonstrates UVLO, Output Short Protection, and Overload Clip the current probe across the wire connecting the HB LED string to the EV kit. 7) Turn on the power supply and set to a voltage greater than the maximum HB LED string voltage, but less than the 65V maximum input voltage. 8) Use the screwdriver to turn the potentiometer until DVM2 reads 1.2V. 9) Measure the HB LED current using the current probe and verify that current is 2A. Features ● 4.5V to 65V Input Voltage ● Drives 1 to 16 LEDs ● Demonstrates Current-Limit and Thermal-Shutdown Features ● Proven PCB Layout and Thermal Design ● Fully Assembled and Tested Quick Start Required Equipment ● MAX20078 EV kit ● 5V to 65V, 4A DC power supply ● Two digital voltmeters (DVM1, DVM2) ● Series-connected HB LED string rated to no less than 2.5A 10) Verify DVM1 shows the expected LED string voltage. 11) Use the screwdriver to turn the potentiometer until DVM2 reads 0.7V. 12) Measure the HB LED current using the current probe and verify that current is 1A. ● Current probe to measure the HB LED current ● Potentiometer ● Small flat-blade screwdriver to turn the potentiometer wiper-adjustment pin 19-8972; Rev 0; 3/17 Ordering Information appears at end of data sheet. MAX20078 Evaluation Kit Evaluates: MAX20078 Table 1. MAX20078 EV Kit Jumper Descriptions (J1, JU1–JU4) JUMPER SHUNT POSITION J1 1-2 Allows the connection of an external 5V (4.5V to 5.5V) supply to VCC. The internal LDO is not used. 2-3* The internal VCC LDO is powered from the input voltage applied on IN pin of the device. Open JU3 REFI pin is now connected to a voltage-divider from VCC to ground. Adjusting R8 allows programming the LED current from 0 to 2.2A. Open Disconnects the REFI pin of the device from the external voltage-divider on the VCC pin. Allows the user to apply an external voltage to set the LED current level. Open* No HUD application. Turning on Q3 does not short the output. 1-2 Allows testing of the device in HUD applications. Allows shorting the output by turning on Q3. 1-2* DIM pin pulled up to VCC through a 10kΩ resistor. 2-3 Open JU4 VCC unconnected. Do not leave J1 open. 1-2* JU1 JU2 DESCRIPTION Open* 1-2 DIM pin pulled up to VIN through a 10kΩ resistor. DIM pin of the device not connected. DIM pin of the device not synchronized to HUD_PWM signal. DIM pin of the device synchronized to HUD_PWM signal. *Default position. Detailed Description The MAX20078 EV kit demonstrates the MAX20078 synchronous buck controller for high-power HB LED drivers. The buck controller consists of a fully synchronous step-down converter with external MOSFETs, and can drive a series string of LEDs at currents as high as 30A. The buck controller uses a proprietary average current-modecontrol scheme to regulate the inductor current. This control method does not need any control-loop compensation, while maintaining nearly constant switching frequency. Inductor current sense is achieved by sensing the current in the bottom synchronous n-channel MOSFET. It does not require any current sense at high voltages. The buck controller offers both analog and PWM dimming. The EV kit is configured to deliver up to 2A to a series LED string. The string forward voltage can vary from 3V to 55V. Analog Dimming Control (ICTRL) The EV kit demonstrates the analog dimming feature of the buck controller. R7 and R8 form a resistor-divider between VCC and AGND. R7 is a 10kΩ resistor and R8 is a 10kΩ potentiometer, with the wiper shorted to the high side of the potentiometer. Install the shunt on JU1 (see Table 1 for jumper descriptions). Using a flat-blade screwdriver, turn the wiper-adjustment pin clockwise to increase the voltage on the REFI input. Turn the wiper-adjustment pin counterclockwise to decrease the voltage on the REFI input. The REFI input allows for analog dimming of the HB LED string. A REFI input voltage of ≤ 0.2V turns off the LED driver, an input voltage between 0.2V and 1.2V provides linear dimming of the HB LED string, and an input voltage > 1.2V sets the HB LED string current to maximum current (based on the current-sense resistor). Alternatively, the analog dimming input can be set with a power supply. Remove the shunt on JU1 and connect an external power supply directly to the REFI PCB pad to perform analog dimming with a power supply. Do not violate the absolute maximum voltage rating of VCC + 0.3V (refer to the Absolute Maximum Ratings section in the MAX20078 IC data sheet). www.maximintegrated.com Maxim Integrated │  2 MAX20078 Evaluation Kit Pulse-Dimming Input (DIM) The EV kit demonstrates the PWM dimming feature of the buck controller. Install a shunt across pins 1-2 on JU3; JU3 pins 2-3 should be open. Connect a PWM signal to the PWM PCB pad. Vary the duty cycle to increase or decrease the intensity of the HB LED string. The DIM input of the device has a 2V (max) rising threshold and a 0.8V (min) falling threshold, and is compatible with 3.3V and 5V logic-level signals. The DIM input is pulled up to VCC through the external 10kΩ resistor on the EV kit when JU3 is installed across pins 1-2. The DIM input can also be pulled up to VIN by moving the jumper on JU3 to pins 2-3 (see Table 1 for jumper descriptions). Fault Indicator The EV kit demonstrates the fault-protection features of the buck controller, which offer shorted-LED, open-LED, and overtemperature protection. The FLT output is an open-drain, active-low fault indicator. Refer to the FLT Flag section in the MAX20078 IC data sheet for more information. Current Monitor Output The EV kit also demonstrates the current-monitor output feature of the buck controller. Refer to the Current Monitor section in the MAX20078 IC data sheet for more information. www.maximintegrated.com Evaluates: MAX20078 External VCC input The EV kit demonstrates operation of the buck controller with an external VCC input. In this case, the internal LDO is not used. Move the shunt to pins 1-2 on J1 (the IN and VCC pins of the buck controller are shorted together). Apply an external power supply between 4.6V and 5.5V on the VCC PCB pad to allow switching of the device. HUD Applications The EV kit can also be tested for HUD applications. Remove capacitor C17 and any pulsating signals on the DIM PCB pad and install a shunt across pins 1-2 on JU2. The output capacitor is now reduced to 0.1µF. The LEDs can be turned on and off extremely fast by applying the PWM signal on the HUD_PWM PCB pad instead of the DIM PCB pad. The jumper on JU3 should be placed across pins 2-3. The DIM input of the device can be synchronized to the leading edge of the HUD_PWM signal by installing a jumper across pins 1-2 on JU4 (see Table 1 for jumper descriptions). Ordering Information PART MAX20078EVKIT# TYPE EV Kit #Denotes RoHS compliant. Maxim Integrated │  3 MAX20078 Evaluation Kit Evaluates: MAX20078 MAX20078 EV Kit Bill of Materials DESIGNATION QTY C1 1 C2 1 C3 1 C4 1 C5 C6, C10 C7 1 2 1 C8, C19 2 C9, C18 2 C11, C12, C13, C14, C15 0 C17 1 D1 1 D2 1 D3 J1, JU3 JU1, JU2, JU4 2 3 L1 1 Q1, Q2 2 Q3 1 R1 R2, R3 1 2 R4 1 R5 R6 R7, R9, R10, R12 1 1 4 R8 1 R11 R13 R14, R15 R16, R17, R18 1 1 0 3 U1 1 U3 1 — — 5 1 www.maximintegrated.com DESCRIPTION 0.1uF ±10%, 250V X7R ceramic capacitors (1210) Murata GRM32DR72E104KW01L 2.2uF ±10%, 10V X7R ceramic capacitor (0603) 470pF ±5%, 50V C0G ceramic capacitor (0603) AVX 06035A471JAT2A 0.22uF ±10%, 50V X7R ceramic capacitors (0603) TDK C1608X7R1H224K080 0.1uF ±10%, 100V X7R ceramic capacitors (0805) 1.0uF ±10%, 10V X7R ceramic capacitor (0603) 2200pF ±10%, 50V X7R ceramic capacitors (0603) 2.2uF ±10%, 100V X7R ceramic capacitors (1210) Murata GRM32ER72A225KA35 TDK CGA6N3X7R2A225K230 0.1uF ±10%, 50V X7R ceramic capacitors (0603) Not installed capacitor (0603) 1.0uF ±10%, 100V X7R ceramic capacitor (1206) Murata GRM31CR72A105KA01 TDK C3216X7R2A105K160 80V, 1A schottky diode (SMA) Diodes Inc. B180-13-F 100V, 1A schottky diode (DO-214) Micro Commercial Components SS110-TP 75V, 0.3A Diode (SOD-323) Diodes Inc 1N4148WS-7-F 3 pin header 2 pin header 47 uH, 5.4A ferrite core inductor Coilcraft MSS1278T-473ML 80V, 0.107 ohm Logic Level MOSFET (LFPAK) NXP BUK9Y107-80E 60V, 4A N-channel Logic Level MOSFET (SOT-223) Fairchild Semiconductor NDT3055L 47.5k ±1% resistor (0603) 4.7ohm ±5% resistor (0603) 0.1 ±1% sense resistor (1206) Panasonic ERJ8BWFR100 453k ±1% resistor (0603) 24.9k ±1% resistor (0603) 10k ±1% resistor (0603) 10k potentiometer, through hole radial lead Bourns 3296W-1-103LF 1.0 ohm ±1% resistor (0603) 100 ohm ±5% resistor (0603) Not installed resistor (0603) 0ohm jumper (0603) Synchronous Buck Controller for High-Power HB LED Drivers (TQFN16-EP) Maxim MAX20078ATE/V+ 7A Sink, 3A Source, 12ns, SOT23 MOSFET Drivers (SOT23-6) Maxim MAX15070AAUT/V+ Shunts PCB: MAX20078 EVKIT Maxim Integrated │  4 REFI FAULT DIM AGND R8 10K REFI DIM 1 PGND 2 3 R7 10K JU1 JU3 VCC 2 1 1 3 VCC FAULT R10 10K R1 47.5K REFI FAULT DIM PGND HUD_PWM LED+ CURRENT_MONITOR 10K R9 C18 0.1UF C3 470PF CURRENT MONITOR VIN 2 C2 2.2UF C19 2.2UF IOUTV R14 OPEN 10 FLT DIM 5 11 REFI TON 6 8 VCC 15 EP HUD_PWM LED+ CURRENT MONITOR C10 1UF C16 OPEN C9 0.1UF C1 0.1UF 1 3 16 12 13 7 CSP CSN OUT AGND VIN VCC VIN VCC 3 LX DL PGND AGND 2 DH U1 MAX20078 D1 C 4.7 D3 R3 A AGND AGND PGND C12 OPEN R16 0 R17 0 A 4 C14 OPEN R4 0.1 C15 OPEN 4 Q2 Q1 BUK9Y107-80E 1N4148WS-7-F C 0 R18 4.7 R2 B180-13-F D G S BUK9Y107-80E G S D R15 OPEN C17 1UF LED+ R6 24.9K D2 SS110-TP C13 OPEN 47UH C5 0.1UF L1 C11 OPEN C4 0.22UF A C J1 PEC03SAAN 2 4 IN 17 1 BST 9 C8 2.2UF 14 5 1 2 3 5 1 2 3 JU2 2 Q3 NDT3055L R5 453K 1 DIM S D 4 2 3 www.maximintegrated.com G 1 2 JU4 1 4 5 C7 2200PF R13 100 GND N_OUT V+ P_OUT U3 MAX15070AAUT/V+ R11 1 6 2 VIN 3 IN- VCC 1 IN+ R12 10K HUD_PWM C6 1UF VCC MAX20078 Evaluation Kit Evaluates: MAX20078 MAX20078 EV Kit Schematic Maxim Integrated │  5 MAX20078 Evaluation Kit Evaluates: MAX20078 MAX20078 EV Kit PCB Layouts MAX20078 EV Kit Component Placement Guide—Component Side MAX20078 EV Kit PCB Layout—Component Side www.maximintegrated.com Maxim Integrated │  6 MAX20078 Evaluation Kit Evaluates: MAX20078 MAX20078 EV Kit PCB Layouts (continued) MAX20078 EV Kit PCB Layout—AGND Layer 2 MAX20078 EV Kit PCB Layout—Layer 3 www.maximintegrated.com Maxim Integrated │  7 MAX20078 Evaluation Kit Evaluates: MAX20078 MAX20078 EV Kit PCB Layouts (continued) MAX20078 EV Kit PCB Layout—Solder Side www.maximintegrated.com Maxim Integrated │  8 MAX20078 Evaluation Kit Evaluates: MAX20078 Revision History REVISION NUMBER REVISION DATE 0 3/17 DESCRIPTION Initial release PAGES CHANGED — For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2017 Maxim Integrated Products, Inc. │  9