19-1243; Rev 1; 10/08 MAX16831 Evaluation Kit The MAX16831 evaluation kit (EV kit) demonstrates the MAX16831 current-mode, high-brightness LED (HBLED) driver IC. The MAX16831 EV kit is configured as a step-down/step-up (buck-boost) topology circuit with peak inductor current and average LED current control for external LEDs. The MAX16831 EV kit operates from a DC supply voltage of 9V to 40V and is configured to deliver 1A of current. The maximum output voltage of the LED string can be up to 28V. The MAX16831 EV kit can be configured for analogcontrol PWM or digital PWM dimming operation using either an analog linear DC voltage or a digital PWM input signal to control the LEDs' brightness. This EV kit has an undervoltage lockout (UVLO) feature that disables the EV kit and overvoltage protection that protects the circuit under no-load conditions. The EV kit circuit also features a clock output and features an input for synchronizing to an external clock. The MAX16831 EV kit is a fully assembled and tested surface-mount printed-circuit board (PCB). Caution: Do not power up the MAX16831 EV kit without connecting a load to the LED+ and LEDPCB pads. Features o 9V to 40V Wide Supply Voltage Range o 1A Output Current o Analog-Control PWM Dimming o PWM Dimming Control o Output Overvoltage Protection o Buffered Clock Output o Lead-Free and RoHS Compliant o Fully Assembled and Tested Ordering Information PART TYPE MAX16831EVKIT+ EV Kit +Denotes lead-free and RoHS-compliant. Warning: Voltages exceeding 42V may exist on the LED+ and LED- output pads. Component List DESIGNATION QTY DESCRIPTION C1, C3, C4, C5, C15 5 0.1F 10%, 50V X7R ceramic capacitors (0603) Murata GRM188R71H104K C2 1 1F 10%, 16V X7R ceramic capacitor (0603) Murata GRM188R71C105K C6, C14 2 1000pF 10%, 50V X7R ceramic capacitors (0603) Murata GRM188R71H102K 1 10F 10%, 16V X7R ceramic capacitor (1206) Murata GRM31CR71C106K 1 100F 20%, 50V electrolytic capacitor (10.3mm x 10.3mm) Panasonic EEVFCIH101P 1 10F 10%, 50V X7S ceramic capacitor (1210) Taiyo Yuden UMK325C7106KM C7 C8 C9 C10, C11, C12 3 4.7F 10%, 100V X7R ceramic capacitors (2220) Murata GRM55DR61H106K DESIGNATION QTY DESCRIPTION C13 1 0.047F 10%, 50V X7R ceramic capacitor (0603) TDK C1608X7R1H473K C16, C17 2 100pF 5%, 50V C0G ceramic capacitors (0603) Murata GQM1885C1H101J D1 1 300mA, 100V diode (SOD123) Diodes Inc. 1N4148W-7-F D2 0 Not installed, diode (SOD123) D3 1 3A, 100V Schottky diode (PowerDI) Diodes Inc. PDS3100 D4 1 1A, 100V Schottky diode (SMA) Diodes Inc. B1100-13-F JU1 1 2-pin header L1 0 Not installed, inductor L2 1 10H, 9.2A inductor Sumida CDEP147NP-100MC-95 N1 1 60V, 3.2A n-channel MOSFET (6-pin TSOP) Vishay Si3458DV-E3 ________________________________________________________________ Maxim Integrated Products 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. 1 Evaluates: MAX16831 General Description Evaluates: MAX16831 MAX16831 Evaluation Kit Component List (continued) DESIGNATION QTY DESCRIPTION DESIGNATION QTY DESCRIPTION R8 0 Not installed, resistor (0805) R9 1 280k 1% resistor (0603) N2 1 100V, 42A n-channel MOSFET (D-Pak) International Rectifier IRLR3110Z N3 0 Not installed, MOSFET (D-Pak) R10, R15 2 4.99k 1% resistors (0603) R1 1 73.2k 1% resistor (0603) R11 1 1k 1% resistor (0603) R2 1 12.4k 1% resistor (0603) R12 1 3.32k 1% resistor (0603) 1 42.2k 1% resistor (0603) 1 0.1 1%, 500mW sense resistor (1206) IRC/TT LRC-LR-1206LF-01-R100-F R13 R3 R14 1 100k potentiometer (single turn) R4 1 100 5% resistor (0603) U1 1 R5 1 1 5% resistor (0603) Current-mode HBLED driver (32 TQFN-EP*) Maxim MAX16831ATJ+ 2 0.04 1%, 2W sense resistors (2512) IRC/TT LRC-LR-2512LF-01-R040-F -- 1 Shunt (JU1) -- 1 PCB: MAX16831 Evaluation Kit+ R6, R7 *EP = Exposed pad. Component Suppliers SUPPLIER PHONE WEBSITE Diodes, Inc. 805-446-4800 International Rectifier 310-322-3331 www.diodes.com www.irf.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 Sumida Corp. 847-545-6700 www.sumida.com TDK Corp. 847-803-6100 www.component.tdk.com Vishay 402-563-6866 www.vishay.com Note: Indicate that you are using the MAX16831 when contacting these component suppliers. Quick Start Recommended Equipment Before beginning, the following equipment is needed: * * * * 9V to 40V, 4A power supply Two digital voltmeters A series-connected LED string rated at 1A (28V max) A current probe to measure LED current Procedures The MAX16831 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 completed and do not power up the MAX16831 EV kit without connecting a load to the LED+ and LED- PCB pads. 2 Warning: Voltages exceeding 42V may exist on the LED+ and LED- output pads. 1) Verify that a shunt is installed across jumper JU1 (analog dimming control). 2) Connect the power supply's positive terminal to the VIN PCB pad on the EV kit. Connect the power supply's ground terminal to PGND PCB pad. 3) Connect the digital voltmeters across the VIN and PGND PCB pads and the LED+ and LEDPCB pads. 4) Connect the anode of the LED string to the LED+ pad. 5) Connect the cathode of the LED string to the LED- pad. _______________________________________________________________________________________ MAX16831 Evaluation Kit 7) Turn on the power supply and increase the input voltage to 9V. Setting External LED Current Resistor R3 sets the MAX16831 EV kit average LED current to 1A. Use the following equation to calculate R3 when reconfiguring the LED current: 8) Adjust potentiometer R14 to obtain the desired LED current duty cycle. 9) Measure the voltage between the LED+ and LEDPCB pads. R3 = where ILED is the LED current. Detailed Description The MAX16831 evaluation kit (EV kit) demonstrates the MAX16831 current-mode HBLED driver IC. The MAX16831 EV kit is configured in a step-down/step-up (buck-boost) topology with peak current control and average current control for a string of user-supplied external HBLEDs. The MAX16831 EV kit operates from a DC supply voltage of 9V to 40V and requires up to 4A. The circuit is configured to deliver 1A of current into series LED string with a maximum 28V forward voltage. The EV kit sets the maximum series inductor current to 8.3A using parallel resistors R6 and R7. The average LED current is set to 1A using resistor R3. A CLKOUT PCB pad is available to monitor the oscillator frequency. A DIM PCB pad is also provided for PWM dimming operation of the external LEDs and to monitor the analog DC voltage applied at the MAX16831 IC DIM pin. LED Dimming Control LED dimming can be achieved on the MAX16831 EV kit by applying a digital PWM signal or an analog DC voltage at the DIM PCB input pad. Jumper JU1, potentiometer R14, resistor R15, and capacitor C15 configure the MAX16831 EV kit for analog-control PWM dimming operation. Place a shunt across jumper JU1 to set the EV kit for analog-control PWM dimming and adjust potentiometer R14. The analog DC voltage at the DIM PCB pad sets the duty cycle of the LED current, which controls the external LED brightness. The MAX16831 IC DIM pin voltage can be monitored by placing a voltmeter across the DIM and AGND PCB pads. Use the following equation to calculate the voltage at the DIM PCB pad, which is necessary to program the LED output current duty cycle, D: Undervoltage Lockout (UVLO) The MAX16831 EV kit's UVLO threshold is configured to 8.3V using resistors R1 and R2. The UVEN PCB pad can be used to disable the EV kit circuit by connecting UVEN to AGND. To configure the circuit to a different UVLO threshold, refer to the Setting the UVLO Threshold section in the MAX16831 IC data sheet. Peak Inductor Current-Limit Setting The parallel combination of current-sense resistors R6 and R7 sets the EV kit's peak inductor current limit to 8.3A. Use the following equation to calculate the total resistance needed to reconfigure the inductor peak current limit: R TOTAL = 160mV IPEAK where IPEAK is the inductor peak current and RTOTAL is the total parallel resistance placed at the R6 and R7 PCB pads. Refer to the ILIM and HICCUP Comparator section in the MAX16831 IC data sheet for additional information on setting the peak current-limit threshold. 107mV ILED DIM (D x 2.6V) + 0.2V where DIM is the analog DC voltage at the MAX16831 EV kit DIM PCB pad in volts, and D is the duty cycle of the LED output current. When operating the MAX16831 EV kit with analog-control PWM dimming, the LED dimming frequency is internally set by the MAX16831 IC to 200Hz. Remove the shunt at jumper JU1 to control LED dimming using a digital PWM signal at the DIM PCB pad. Apply a digital PWM signal with a 3.2V to 15V logic-high level in the 80Hz to 2kHz frequency range and adjust the duty cycle to adjust the LED brightness. See Table 1 for jumper JU1 setting for LED dimming operation. Table 1. MAX16831 LED Dimming Operation (Jumper JU1) SHUNT POSITION EV KIT DIMMING OPERATION Not installed PWM signal applied at DIM PCB pad Installed Analog DC voltage adjusted using R14 _______________________________________________________________________________________ 3 Evaluates: MAX16831 6) Clip the current probe across the LED+ wire to measure the LED current. Evaluates: MAX16831 MAX16831 Evaluation Kit CLK OUTPUT Output Overvoltage Protection The MAX16831 EV kit features a buffered digital clock output, CLKOUT. The MAX16831 PWM clock frequency is programmed to 300kHz by resistor R13. To synchronize the MAX16831 EV kit to an external clock signal, connect a clock signal with a 2.8V to 5.5V logic level and 125kHz to 500kHz square wave at the RTSYNC PCB pad. Refer to the Oscillator, Clock, and Synchronization section in the MAX16831 IC data sheet for information on setting the MAX16831 IC PWM frequency. The maximum voltage on the LED+ PCB pad is limited to 70.8V, with respect to GND, by a feedback network formed by resistors R9 and R10. When the voltage at LED+ exceeds the programmed 70.8V threshold, PWM switching is terminated and no further energy is transferred to the load connected between LED+ and LED-. Refer to the Setting the Overvoltage Threshold section in the MAX16831 IC data sheet for setting the overvoltage threshold. 4 If the EV kit is turned on with no load, the voltage at LED+ may rise to unsafe levels. Even though the EV kit has overvoltage protection, connect the specified load before powering up the EV kit. _______________________________________________________________________________________ CLKOUT RTSYNC DIM AGND C15 0.1F C2 1F AGND PGND C17 100pF R15 4.99k 1% C1 0.1F R13 42.2k 1% JU1 2 R14 100k 3 1 R2 AGND 12.4k 1% 8 7 6 5 4 3 2 CLKOUT RTSYNC DIM REF AGND REG1 UVEN N.C. 9 10 11 COMP 12 REG2 30 29 U1 28 C14 1000pF 13 R12 3.32k 1% 27 C5 0.1F 14 C13 0.047F R11 1k 1% MAX16831 HI 31 C4 0.1F CLMP 32 VCC I.C. 1 I.C. R1 73.2k UVEN 1% I.C. I.C. CSFB LED+ R3 0.1 1% 26 15 OV REG2 25 VIN R10 4.99k 1% DGT N.C. DRV DRI SNS+ SNS QGND 16 17 CS+ C3 0.1F SGND PGND CS LO SGND VIN 18 19 20 21 22 23 24 3 R8 OPEN D2 OPEN D1 C16 100pF 1 1 C7 10F 16V R5 1 C6 1000pF 2 2 12 R4 100 N1 56 R9 280k 1% 1 N2 REG2 4 3 4 DRV_N3 R6 0.04 1% DRV_N3 SNS+_IN LED- 3 R7 0.04 1% 1 4 N3 OPEN L2 10H 1 C10 4.7F 100V D3 2 SNS+_IN 3 C8 100F 50V L1 SHORT C11 4.7F 100V C9 10F 50V 1 2 C12 4.7F 100V D4 VIN LED+ LED+ Evaluates: MAX16831 VIN MAX16831 Evaluation Kit Figure 1. MAX16831 EV Kit Schematic _______________________________________________________________________________________ 5 Evaluates: MAX16831 MAX16831 Evaluation Kit Figure 2. MAX16831 EV Kit Component Placement Guide--Components Side Figure 3. MAX16831 EV Kit PCB Layout--Component Side 6 _______________________________________________________________________________________ MAX16831 Evaluation Kit Evaluates: MAX16831 Figure 4. MAX16831 EV Kit PCB Layout--GND Layer 2 Figure 5. MAX16831 EV Kit PCB Layout--VCC Layer 3 _______________________________________________________________________________________ 7 Evaluates: MAX16831 MAX16831 Evaluation Kit Figure 6. MAX16831 EV Kit PCB Layout--Solder Side 8 _______________________________________________________________________________________ MAX16831 Evaluation Kit REVISION NUMBER REVISION DATE 0 11/07 Initial Release -- 1 10/08 Component C9 part number change. 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 (c) 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. Evaluates: MAX16831 Revision History