MAX1729EVKIT

19-1406; Rev 1; 1/99 MAX1729 Evaluation Kit The MAX1729 evaluation kit (EV kit) is a low-power, step-up DC-DC converter followed by a low-dropout linear regulator. It accepts a positive input voltage between 2.7V to 5.5V and converts it to an output voltage ranging from 2.5V to 16V. The output voltage is dynamically adjustable through an external 3kHz to 12kHz pulse-width-modulated (PWM) control signal. An on-chip temperature sensor provides compensation for display temperature characteristics. This makes the MAX1729 ideally suited for electrically controlled birefringence (ECB) and LCD bias-supply generation Features ♦ High-Accuracy Reference Voltage (±1%) ♦ On-Chip Temperature-Sensor Output ♦ 2.7V to 5.5V Input Range ♦ Dynamic Control of Output Voltage ♦ 0.4µA Typical Shutdown Current ♦ 10-Pin µMAX Package ♦ Surface-Mount Construction ♦ Fully Assembled and Tested Ordering Information Component List DESIGNATION QTY DESCRIPTION C1, C6 2 0.1µF ceramic capacitors C2 0 Not installed C3 1 0.068µF ceramic capacitor C4, C7 2 1µF ceramic capacitors Taiyo Yuden TMK316BJ105KL PART TEMP. RANGE MAX1729EVKIT 0°C to +70°C IC PACKAGE 10µMAX Quick Start C5 1 1000pF ceramic capacitor JU1 1 3-pin jumper The MAX1729 EV kit is a fully assembled and tested surface-mount board. Follow the steps below to verify board operation. Do not turn on the power supply until all connections are completed. L1 1 220µH inductor Murata LQH3C221K34 1) Connect a 2.7V to 5.5V supply to the pads marked VIN and GND. R1–R5 0 Not installed U1 1 MAX1729EUB 2) Connect a voltmeter and load, if any, to the VOUT pad. 3) Place the shunt on JU1 across pins 2 and 3. 4) Turn on the power and verify that the output voltage is approximately 16.35V. Component Suppliers SUPPLIER PHONE FAX Murata 814-237-1431 814-238-0490 Taiyo Yuden 408-573-4150 408-573-4159 5) For other output voltages, refer to the Output Voltage Control section. Detailed Description Jumper Selection Jumper JU1, in the 2-3 position, connects CTLIN to VIN. This places the output voltage at maximum and is equivalent to applying a PWM signal with a 100% duty cycle. In the 1-2 position, CTLIN is connected to GND. This places the MAX1729 into shutdown mode and is equivalent to applying a PWM signal with a 0% duty cycle. When applying a PWM signal to the CTLIN pad, the shunt must be removed from jumper JU1. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. Evaluates: MAX1729 General Description Evaluates: MAX1729 MAX1729 Evaluation Kit Temperature Compensation Table 1. Jumper JU1 Functions JUMPER JU1 JUMPER POSITION The MAX1729 EV kit includes a TC pad, which is a temperature-sensor output. This pad is used to compensate for ECB color or LCD contrast variations caused by changes in temperature. In internal feedback mode, this output is read by an external ADC and used to adjust the duty cycle of the PWM control signal. In external feedback mode, this output is summed directly into the feedback-resistor network. Refer to the MAX1729 data sheet to determine feedback-resistor values. FUNCTION 2-3 CTLIN = high, MAX1729 enabled. Output voltage at maximum value. 1-2 CTLIN = low, MAX1729 in shutdown mode. Open Drive CTLIN pad with external PWM signal. Output Voltage Control The output voltage of the MAX1729 EV kit is dynamically adjustable through a 3kHz to 12kHz PWM control signal applied to the CTLIN pad. The output is adjustable from 2.5V to 16V in internal feedback mode or from 2.5V to 18V in external feedback mode. The EV kit is initially set up for internal feedback operation. To use the EV kit for external feedback operation, cut the traces across R2 and R4 and insert resistors R1–R5. Refer to the MAX1729 data sheet to determine the resistor values. L1 220µH 1 VIN C1 0.1µF 10 C2 OPEN GND 3 C6 0.1µF VIN IN LX PS 9 8 C3 0.068µF U1 GND MAX1729 REF OUT 7 3 CTLIN 2 JU1 1 VOUT C4 1µF R1 OPEN 6 CTLIN FB TC COMP 2 4 R4 SHORT (PC TRACE) 5 R5 OPEN R2 SHORT (PC TRACE) R3 TC C7 1µF OPEN C5 1000pF Figure 1. MAX1729 EV Kit Schematic 2 _______________________________________________________________________________________ MAX1729 Evaluation Kit Evaluates: MAX1729 BMG 1.0" 1.0" Figure 2. Component Placement Guide—Component Side Figure 3. PC Board Layout—Component Side 1.0" Figure 4. PC Board Layout—Solder Side _______________________________________________________________________________________ 3 Evaluates: MAX1729 MAX1729 Evaluation Kit NOTES 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. 4 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.