MIC4826/4827 Micrel MIC4826/4827 Evaluation Board High Voltage EL Driver By William Mai General Description Requirements The MIC4826 and MIC4827 are high voltage EL (Electroluminescent) drivers designed for driving EL lamps of up to 6 in2 (typically). The input supply voltage range is from 1.8V to 5.5V, making both devices suitable for one-cell Li-Ion and two-cell NiCad/NiMH/Alkaline applications. Both devices use a single inductor and a minimum number of passive components. The nominal AC output voltage that is applied to the EL lamp is 160V for the MIC4826 and 180V for MIC4827. The chip can be enabled or disabled by connecting the resistor on RSW and REL to VDD or ground, respectively. The MIC4826/7 feature separately programmable switch frequency and EL frequency through external resistors. This allows the user to optimize the efficiency and enhance the brightness of the lamps. The MIC4826/7 evaluation board requires an input power source which should be able to supply a minimum of 0.5A and a maximum voltage of 5.5V. Precautions The evaluation board does not have input reverse polarity protection. Applying a negative voltage at the VIN terminal (with respect to ground) may permanently damage the components on the board. The input capacitor voltage’s rating is 6.3V. Exceeding this voltage for an extended period of time will damage the capacitor. The COUT capacitor is rated at 100V. Do not exceed 100V. Circuit Operation The MIC4826/7 are essentially comprised of two parts, a boost converter and an H-bridge driver. The boost converter steps up the input voltage to 80V (typical) for the MIC4826 and 90V (typical) for the MIC4827. The H-bridge driver produces an AC voltage of 160VPP (typical) for the MIC4826 and 180VPP (typical) for the MIC4827 to drive the EL lamp at a frequency that is programmed by the resistor on REL. Schematic JP2 1 2 3 1 2 3 R4 1M R5 2M R6 3.32M U1 MIC4826 or MIC4827 C2 10µF 6.3V JP1 R1 562k R2 442k D1 BAS20W L1 220µH JP3 J1 VIN R3 332k 4 C1 0.01µF 50V JP4 3 5 2 6 1 4 3 5 2 1 6 C3 0.1µF/100V 1 VDD SW 5 2 RSW CS 6 3 REL VA 8 J4 4 GND VB 7 J5 JP5 EL LAMP 2 in2 J2, J3, J6 Figure 1. High Voltage EL Driver Evaluation Board Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com September 2001 1 MIC4826/4827 Evaluation Board MIC4826/4827 Micrel EL Frequency Setting Output Capacitor Three EL frequencies may be selected by placing the shorting jumper across the proper pins of header JP5 (108Hz, 180Hz or 360Hz). The EL frequency determines the color of the EL lamp. In general, increasing the EL lamp frequency will increase the input current. See Tables 1 and 2. Both the output capacitance and the capacitor’s ESR (equivalent series resistance) affect the output ripple. The ESR mainly contributes to the high frequency output ripple while the capacitance contributes to the low frequency output ripple. In this evaluation board, a 0.1µF/100V ceramic output capacitor is used for wide input voltage range applications. A narrow input voltage range such as the Li-Ion battery range (3.0V to 4.2V) can use a small output capacitor, 0.01µF/100V. Switching Frequency Setting Three switching frequencies may be selected by placing the shorting jumper across the pins of header JP4 (64KHz, 81KHz or 108KHz). Tables 1 and 2 show the relationship between the switching frequency, the input voltage range, input current range, and the EL lamp frequency. Diode The BAS20W is used for this evaluation board. It has 100nA maximum peak reverse current at 150V in SOT-323 package. For cost-sensitive applications, a lower reverse-voltage rated diode may be used. Enable/Disable Connecting JP1 and JP2 to VIN enables the EL driver. Connecting JP1 and JP2 to GND disables the EL driver. fEL REL fSW RSW VIN(MIN) VIN(MAX) Input Current Range (Hz) (MΩ) (KHz) (KΩ) (V) (V) (mA) 108 3.32 64 562 1.8 5.5 8-32 180 2 64 562 2.2 5.5 12-33 360 1 64 562 2.8 5.5 21-42 108 3.32 81 442 2.0 5.5 8-29 180 2 81 442 2.3 5.5 12-32 360 1 81 442 2.9 5.5 20-40 108 3.32 108 332 2.4 5.5 8-24 180 2 108 332 2.7 5.5 12-28 360 1 108 332 3.2 5.5 20-37 VA (50V/div) VB (50V/div) RSW = 562k REL = 3.32M VA – VB (50V/div) VA – VB (50V/div) VB (50V/div) VA (50V/div) Table 1. Typical MIC4826 Performance for 160VPP Output RSW = 562k REL = 3.32M TIME (2ms/div) TIME (2ms/div) Figure 1. Typical MIC4826 Output Waveform for VIN = 1.8V MIC4826/4827 Evaluation Board Figure 2. Typical MIC4826 Output Waveform for VIN = 5.5V 2 September 2001 MIC4826/4827 Micrel fEL REL fSW RSW VIN(MIN) VIN(MAX) Input Current Range (Hz) (MΩ) (KHz) (KΩ) (V) (V) (mA) 108 3.32 64 562 2 5.5 7-36 180 2 64 562 2.3 5.5 9-41 360 1 64 562 3.1 5.5 27-48 108 3.32 81 442 2.2 5.5 7-34 180 2 81 442 2.5 5.5 16-39 360 1 81 442 3.2 5.5 27-47 108 3.32 108 332 2.7 5.5 8-27 180 2 108 332 3 5.5 10-32 360 1 108 332 3.6 5.5 26-41 VA (50V/div) VB (50V/div) VA – VB (50V/div) VA – VB (50V/div) VB (50V/div) VA (50V/div) Table 2. Typical MIC4827 Performance for 180VPP Output RSW = 562k REL = 3.32M TIME (2ms/div) TIME (2ms/div) Figure 3. Typical MIC4827 Output Waveform for VIN = 2.0V September 2001 RSW = 562k REL = 3.32M Figure 4. Typical MIC4827 Output Waveform for VIN = 5.5V 3 MIC4826/4827 Evaluation Board MIC4826/4827 Micrel Printed Circuit Board Top Side Silk Screen Top Side Copper Bottom Side Copper Bill of Materials Item Part Number Manufacturer Description U1 MIC4826BMM or MIC4827BMM Micrel1 High Voltage EL Driver 1 D1 BAS20W Diodes, Inc.2 Diode 1 L1 LQH43CN221K01L Murata3 220µH Inductor 1 C1 GRM39 X7R 103K 50 Murata3 0.01µF, 50V Ceramic 1 C2 GRM40 X5R 106K 6.3 Murata3 10µF, 6.3V Ceramic 1 C3 GRM42-2 X7R 104K 100 Murata3 0.1µF, 100V Ceramic 1 R1 CRCW 0603 5623 FRT1 Vishay-Dale4 562K 1%, 0603 size resistor 1 R2 CRCW 0603 4423 FRT1 Vishay-Dale4 442K 1%, 0603 size resistor 1 R3 CRCW 0603 3323 FRT1 Vishay-Dale4 332K 1%, 0603 size resistor 1 R4 CRCW 0603 1004 FRT1 Vishay-Dale4 1M 1%, 0603 size resistor 1 R5 CRCW 0603 2004 FRT1 Vishay-Dale4 2M 1%, 0603 size resistor 1 CRCW 0603 3324 FRT1 Vishay-Dale4 3.32M 1%, 0603 size resistor JP1,JP2 Sullins Jumpers 2 set of 6 JP3 Sullins Jumper 1 Sullins Jumpers 2 set of 3 R6 JP4,P5 SNT-100-BL-G J1,J2,J3,J6 2551-2-00-01-00-00-07-0 Milmax EL Lamp X533-19 LSI5 Qty 1 Turret Pins 4 EL Lamp 1 1. Micrel Semiconductor, tel: 408-944-0800 2. Diodes, Inc,, tel: 805-446-4800 3. Murata, tel: 800-831-9172 4. Vishay-Dale, tel: 206-452-5664 5. LSI, tel: 603-643-7766 MIC4826/4827 Evaluation Board 4 September 2001 MIC4826/4827 Micrel MICREL INC. TEL 1849 FORTUNE DRIVE SAN JOSE, CA 95131 + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB USA http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. © 2001 Micrel Incorporated September 2001 5 MIC4826/4827 Evaluation Board