MAX16821B Evaluation Kit. Evaluates: MAX16821B. Features

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1 9-967; Rev 0; /07 MAX68B Evaluation Kit General Description The MAX68B evaluation kit (EV kit) is a fully assembled and tested surface-mount printed-circuit board (PCB) designed to evaluate the MAX68B pulsewidth-modulation (PWM) LED driver controller in a boost configuration. The MAX68B EV kit operates from a DC supply voltage of 7V to 4V. The EV kit s output is configured to deliver 660mA of current into series LED string with a maximum forward voltage of 8V. The LED brightness can be dimmed using a digital PWM signal. The EV kit provides an option to configure the MAX68B IC s overvoltage protection, switching frequency, and frequency compensation. The MAX68B EV kit also features a clock output PCB pad to drive a second LED current regulator out-of-phase. C, C5, C6 C 0µF±0%, X7S ceramic capacitors (0) Taiyo Yuden UMK5BJHI06K 0.µF±0%, X7R ceramic capacitor (06) Murata GRM9R7H04K Features 7V to 4V Input-Voltage Range 660mA Output Current Pulse-Width-Modulated LED Current Dimming Resistor-Adjustable Overvoltage Protection and Switching Frequency Clock Output Fully Assembled and Tested PART MAX68BEVKIT+ +Denotes lead-free and RoHS-compliant. Ordering Information TYPE EV Kit Component List L N N µH, 4A inductor Sumida CDEP05-8R8 60V, 5mA n-channel MOSFETs (SOT) Central Semiconductor N700 LEAD-FREE Evaluates: MAX68B C, C4 000pF±0%, 5V X7R ceramic capacitors (060) Murata GRM88R7E0K N5 40V, 4.9A n-channel MOSFET (8-pin SO) Vishay Si4446DY C7 C8 C9, C0 D 0.0µF±0%, X7R ceramic capacitor (060) Murata GRM88R7HK 4.7µF±0%, 6.V X7R ceramic capacitor (060) Murata GRM88R70J475K 0.µF±0%, X7R ceramic capacitors (060) Murata GRM88R7H04K A, 60V Schottky diode (SMA) Diodes Inc. B60A--F N6 60V,.A n-channel MOSFET (6-pin TSOP) Vishay Si458DV-E R 49kΩ ± resistor (060) R, R5, R0 0kΩ ± resistors (060) R 0 Not installed, resistor shorted (060) 4kΩ ± resistor (060) R Ω ±%, 0.5W sense resistor (06) IRC LRC-LRF06LF-0-R007-G Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim s website at

2 MAX68B Evaluation Kit Evaluates: MAX68B R7 0.5Ω ±, 0.5W sense resistor (06) IRC LRC-LRC06LF-0-R50-F R8 Ω ±5% resistor (060) R9 kω ± resistor (060) R.49kΩ ± resistor (060) R.4kΩ ± resistor (060) Component List (continued) Component Suppliers SUPPLIER PHONE WEBSITE Central Semiconductor Corp Diodes Inc IRC Inc Murata Mfg. Co., Ltd Sumida Corp Taiyo Yuden Vishay Note: Indicate that you are using the MAX68B when contacting these component suppliers. R kω ± resistor (060) Maxim PWM LED driver controller U MAX68BATI+ (8-pin thin QFN-EP*, 5mm x 5mm x 0.8mm) PCB: MAX68B Evaluation Kit+ *EP Exposed pad. Quick Start Recommended Equipment Before beginning, the following equipment is needed: 7V to 4V, 4A DC power supply One series-connected LED string rated at 660mA (8V maximum LED voltage) One current probe to measure LED current One voltmeter Procedure The MAX68B 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. ) Connect the positive terminal of the power supply to the pad on the EV kit. Connect the negative terminal of the power supply to the PGND pad next to the pad. ) Connect the anode end of the LED string to the pad. ) Connect the cathode end of the LED string to the LED- pad. 4) Clip the current probe across the string wires to measure the LED current. 5) Turn on the power supply and increase the voltage to 7V or above. 6) Verify that the LED string DC current is approximately 660mA. 7) Measure the voltage between the to LED- PCB pads. Detailed Description The MAX68B EV kit circuit is designed to evaluate the MAX68B PWM LED driver controller. The EV kit is configured in a boost topology and provides 660mA LED current for a string of user-supplied external highbrightness LEDs (HBLEDs) rated up to 8V. The MAX68B EV kit operates from a DC supply voltage of 7V to 8V. The EV kit average input current is set to.75a using resistor R6. The LED current is set to 660mA using resistor R7. A PCB pad is provided for PWM dimming operation of the external LEDs. A CLKOUT PCB pad is also available to drive a second LED current regulator 80 out-of-phase with the first EV kit.

3 MAX68B Evaluation Kit LED Output Current The MAX68B delivers 660mA into an LED string rated up to a maximum of 8V. Resistor R7 sets the MAX68B EV kit LED output current. Use the following equation to calculate R7 when reconfiguring the LED current: R7 where 00mV is the MAX68B regulated SENSE+ to SENSE- differential current-sense voltage and I LED is the desired LED current. Input Current-Limit Setting Current-sense resistor R6 sets the EV kit s circuit average input current limit to.75a. During an overload condition at low line, the MAX68B regulates the average input current to.75a. Use the following equation to calculate a new R6 value when reconfiguring the input current limit: R6 00mV I LED 6. 4mV I IN where I IN is the input current limit. For additional information, refer to the Average Current Limit section in the MAX68A/MAX68B/MAX68C IC data sheet for setting the input current limit when configuring the MAX68B in a boost configuration. LED Brightness Dimming The LED brightness can be dimmed using a PWM signal with a 5V logic-high level and frequency range of 00Hz to 5kHz. Connect the PWM signal to the and PCB pads to control the LEDs brightness. Output Overvoltage Protection The maximum voltage on the pin is limited to V, with respect to GND, by a resistor feedback network formed by resistors R and R. When the voltage at exceeds the programmed V threshold, the low-side driver turns off to prevent current through the LED string connected between and LED-. Use the following equation to calculate R and R resistor values for a new overvoltage threshold: R R ( ) VOV_ LIM VOV VOV where V OV_LIM is the desired overvoltage threshold, R is typically 0kΩ, and V OV is.76v. Switching Frequency The MAX68B EV kit switching frequency (f SW ) is configured to 500kHz by resistor. To reconfigure the MAX68B switching frequency from 5kHz to.5mhz, use the equations below to calculate the new value for : x 0, for 40kΩ fsw 0kΩ x 0, for 0kΩ fsw 500kΩ where f SW is the desired switching frequency. When reconfiguring the MAX68B EV kit switching frequency, other components may need to be changed for proper stable operation. Clock Output The MAX68B EV kit also features a clock output signal that is 80 out-of-phase with respect to MOSFET N5. The clock output is available at the CLKOUT PCB pad. Use the PCB pad as a reference ground for the CLKOUT signal. Output Enable (EN) The MAX68B is enabled through pullup resistor R5. To disable the MAX68B EV kit, connect the EN PCB pad to the pad. Evaluates: MAX68B

4 MAX68B Evaluation Kit Evaluates: MAX68B CLP R kω R 49kΩ N N4 R0 0kΩ R 0kΩ EN C0 0.μF N OUTV CSP C 000pF R.49kΩ R9 kω N R SHORTED 4 I.C. R.4kΩ C7 0.0μF OUTV 5 OVI 6 CLP 7 EAOUT 8 EAN 9 DIFF 0 CSN CSP 4kΩ RT/SYNC 5 LED- SENSE- EN U MAX68B SENSE+ 4 R5 0kΩ C4 000pF IN 6 0 MODE C9 0.μF 8 CLKOUT 7 N.C. N.C. EP 9 7 DH 6 LX 5 BST 4 DL PGND V CC C8 4.7μF C 0.μF 5, 6, 7, 8 4 R8 Ω L 8.8μH N5 PGND 8 V DD D C 0μF PGND CLKOUT R Ω % C5 0μF C6 0μF CSP R7 0.5Ω,, 5, 6 N6 4 Figure. MAX68B EV Kit Schematic 4

5 MAX68B Evaluation Kit Figure. MAX68B EV Kit Component Placement Guide Component Side Figure. MAX68B EV Kit PCB Layout Component Side Evaluates: MAX68B Figure 4. MAX68B EV Kit PCB Layout Solder Side 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, 0 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.