MAX16818 Evaluation Kit. Evaluates: MAX16818

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1 9-08; Rev 0; 6/07 MAX688 Evaluation Kit General Description The MAX688 evaluation kit (EV kit) is a fully assembled and tested surface-mount printed-circuit board (PCB) designed to evaluate the MAX688 pulse-width modulation (PWM) LED driver controller in a buck-boost configuration. The MAX688 EV kit operates from a DC supply voltage of 6V to 8V. The EV kit s output is configured to deliver at least A of current into an 8V series LED string. The LED brightness can be dimmed using a digital PWM signal. The EV kit provides an option to configure the MAX688 IC s overvoltage protection, switching frequency, and frequency compensation. The MAX688 EV kit also features a 80 out-of-phase clock output PCB pad. C.µF ±0%, 0V X7R ceramic capacitor (06) Murata GRMCR7HK C µf ±0%, 0V X7R ceramic capacitor (080) Murata GRMBR7H0M C.7µF ±0%, 6.V X7R ceramic capacitor (060) Murata GRM88R70J7K C 0.7µF ±0%, 6.V X7R ceramic capacitor (060) Murata GRM88R70J7K C 000pF ±0%, 0V X7R ceramic capacitor (060) Murata GRM88R7H0K C6, C7 0µF ±0%, 0V X7R ceramic capacitors (0) Murata GRMDR7H06K C8, C0 0 Not installed, capacitors (060) C9 0.µF ±0%, 6V X7R ceramic capacitor (060) Murata GRM88R7CK C 00pF ±0%, 0V X7R ceramic capacitor (060) Murata GRM88R7HK Features 6V to 8V Input-Voltage Range A Output Current into an 8V LED String Pulse-Width Modulated LED Current Dimming Resistor-Adjustable Overvoltage Protection and Switching Frequency 80 Out-of-Phase Clock Output Fully Assembled and Tested Ordering Information PART TEMP RANGE IC PACKAGE MAX688EVKIT+ 0 C to +70 C* 8 TQFN-EP** +Denotes a lead-free and RoHS-compliant EV kit. *This limited temperature range applies to the EV kit PCB only. The MAX688 IC temperature range is -0 C to + C. **EP = Exposed paddle. Component List C 0.µF ±0%, 6V X7R ceramic capacitor (060) Murata GRM88R7C0K C 00pF ±%, 0V C0G ceramic capacitor (060) Murata GRM88CH0J C 00µF, 0V electrolytic capacitor (8mm x 0.mm) Panasonic EEEFKH0P D 60V, A Schottky diode (SMB) Diodes Inc. B60--F JU -pin header JU -pin header L 8.8µH, A DC inductor Sumida CDEP0-8R8 N 0V,.9A n- channel M OS FE T ( S O8) V i shay S i 6D Y N N 60V, ma n-channel MOSFETs (SOT) Central Semiconductor N700 LEAD-FREE P -0V, -.8A p-channel MOSFET (TSOP-6) Vishay Si67DV-T-E Evaluates: MAX688 Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim's website at

2 MAX688 Evaluation Kit Evaluates: MAX688 Q NPN bipolar transistor (SOT) Fairchild Semiconductor PZT90 Q PNP bipolar transistor (SOT) Fairchild Semiconductor MMBT906 R kω ± resistor (06) R.kΩ ± resistor (060) R, R7, R, R6 0kΩ ± resistors (060) R, R Ω ± resistors (060) R6.99kΩ ± resistor (00) R8 kω ± resistor (00) R9 00kΩ ± resistor (00) R0.kΩ ± resistor (00) R 0kΩ ± resistor (060) R, R kω ±% resistors (080) R 0.007Ω ±%, 0.W sense resistor (00) IRC LRC-LRF00LF-0-R007-G R7 kω ± resistor (060) Component List (continued) R8 kω ± resistor (060) R9 99Ω ± resistor (060) R0 0.Ω ±, 0.W sense resistor (06) IRC LRC-LRC06LF-0-R-F R 0.kΩ ± resistor (060) R 0.kΩ ± resistor (060) R 00kΩ SMT cermet trimmer, turns U MAX688ATI+ (8-pin TQFN-EP, mm x mm) U Voltage-output, high-side currentsense amplifier MAX07TAXK+ (-pin SC70-) U, U Low-voltage, adjustable precision shunt regulators (SOT) Texas Instruments TLAQDBZRQ Shunts PCB: MAX688 Evaluation Kit+ Component Suppliers SUPPLIER PHONE WEBSITE Central Semiconductor Diodes Inc Fairchild Semiconductor IRC, Inc Murata Mfg. Co., Ltd Panasonic Corp Sumida Corp Vishay/Vitramon Note: Indicate that you are using the MAX688 when contacting these component suppliers.

3 MAX688 Evaluation Kit Quick Start Recommended Equipment Before beginning, the following equipment is needed: 6V to 8V, A DC power supply A series-connected LED string rated at A (maximum voltage on the string should not exceed 8V) A current probe to measure LED current One voltmeter Procedure The MAX688 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. ) Verify that a shunt is installed across pins - of jumper JU. ) Verify that no shunt is installed across jumper JU (EV kit on). ) Connect the anode end of the LED string to the LED+ pad. ) Connect the cathode end of the LED string to the LED- pad. ) Clip on the current probe across the string wires to measure the LED current. 6) Connect the positive terminal of the power supply to the VIN pad on the EV kit. Connect the negative terminal of the power supply to the PGND pad next to the VIN pad. 7) Turn on the power supply and increase the voltage to 6V or above. 8) Verify that the LED string current is approximately A. Adjust potentiometer R to obtain A. 9) Measure the voltage between the LED+ to LED- PCB pads. Detailed Description The MAX688 EV kit is designed to evaluate the MAX688 PWM LED driver controller in a buck-boost configuration. The EV kit PCB is designed with two layers and has oz copper traces. All components on the EV kit are installed on the top layer. The EV kit includes an on-board regulating circuit for operation with input voltage between 6V to 8V. The EV kit also includes on-board output overvoltage protection circuitry to limit the output voltage. Input-Voltage Range The MAX688 EV kit can operate from a DC supply voltage of 6V to 8V and requires at least A. The inputvoltage range is jumper selectable (see the Jumper Selection section). Transistor Q, shunt regulator U, and resistors R, R, and R are used to regulate to V when the input voltage to the EV kit is between 6V to 8V. If the minimum input voltage is 8V, jumper JU can be replaced by a shorting wire between pins -. Transistor Q, shunt regulator U, and resistors R, R, and R can be omitted from the EV kit, saving components and reducing the required PCB space. Output Current Range The MAX688 EV kit can deliver up to A into an 8V series LED string. The maximum output current is configurable by sense resistor R. The LED current can be adjusted from 00mA to A using potentiometer R. LED Brightness Dimming The LED brightness can be dimmed using a TTL PWM signal with a frequency range of 80Hz to khz. Connect the TTL dimming signal to the PWMDIM and GND pads to control the brightness of the LEDs. Output Overvoltage Protection The MAX688 EV kit features overvoltage protection circuitry to limit the voltage from LED+ to GND to 6V when the LED string is opened. The overvoltage protection circuitry consists of resistors R6 R0, transistor Q, and shunt regulator U. The overvoltage protection circuitry is nonlatching. Switching Frequency The MAX688 EV kit switching frequency (f SW ) is configured to 600kHz by resistor R. To reconfigure the MAX688 switching frequency from khz to.mhz, replace resistor R using the equation below: For 0kΩ R 00kΩ ( ) R= f SW For 0kΩ R 0kΩ ( ) R= f SW where f SW is the desired switching frequency in Hz. Note: Other component values may need to be changed for proper operation. Refer to the MAX688 IC data sheet for additional information. Evaluates: MAX688

4 MAX688 Evaluation Kit Evaluates: MAX688 Clock Output The MAX688 EV kit also features a digital clock output that is 80 out-of-phase with respect to the highside driver, N. The clock output is available at the CLKOUT PCB pad. Jumper Selection Input-Voltage Range (VIN) Jumper JU selects the input-voltage range for the MAX688 EV kit (see Table for shunt positions). Table. JU Jumper Selection (IN) SHUNT POSITION IN PIN CONNECTED TO VIN VOLTAGE RANGE - VIN 8V to 8V* -** 6V to 8V None (Not allowed) No connect *When operating in the 8V to 8V input-voltage range, jumper JU can be replaced by a shorting wire between pins -. **Default position. 0V Output Enable (EN) Jumper JU controls the output enable pin on the MAX688 IC. The MAX688 output enable pin (EN) is also connected to the overvoltage protection circuitry on the EV kit (see Table for shunt positions). Table. JU Jumper Selection (EN) SHUNT POSITION EN PIN CONNECTED TO EV KIT FUNCTION Installed GND Disabled Not installed* *Default position. Overvoltage protection circuitry (R6 R0, Q, U) Enabled

5 Evaluates: MAX688 MAX688 Evaluation Kit R0.kΩ U R8 kω R9 00kΩ Q R7 0kΩ R6.99kΩ C 0.7μF R Ω R Ω C.7μF C μf JU Q R kω R.kΩ C.μF 0V C 00μF 0V VIN VIN PGND R 0kΩ U C 000pF JU ENABLE SGND CLKOUT R 0kΩ 9 8 C 00pF R 0.kΩ R 00kΩ R 0.kΩ C 0.μF GND RS+ OUT RS- R0 0.Ω VIN N R kω 6 P R kω LED- LED+ PWMDIM SGND R 0kΩ C7 0μF 0V C6 0μF 0V 8 7 N 6 D L 8.8μH PGND SGND SGND SGND OVI R7 kω 9 8 R6 0kΩ 7 N C9 0.μF C8 OPEN N R9 99Ω N R8 kω C 00pF C0 OPEN R 0.007Ω % DH LX CSP CSN CLP EAOUT EAN DIFF SENSE+ SENSE- LIM RT/SYNC CLKOUT EN BST VDD IN N.C. N.C. DL PGOOD V_IOUT MAX688 U MAX07T U Figure. MAX688 EV Kit Schematic

6 MAX688 Evaluation Kit Evaluates: MAX688 Figure. MAX688 EV Kit Component Placement Guide Component Side Figure. MAX688 EV Kit PCB Layout Component Side Figure. MAX688 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. 6 Maxim Integrated Products, 0 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. Boblet