Features. High Voltage EL Driver

Transcription

1 MIC8 Low Input Voltage, 18V PP Output Voltage, EL Driver Final Information General Description s MIC8 is a high output voltage, DC to AC converter, designed for driving EL (Electroluminescent) lamps. The device operates from an input voltage range of 1.8V to 5.5V, making it suitable for 1-cell Li Ion and - or -cell alkaline/nicad/nimh battery applications. The MIC8 converts a low voltage DC input to a 18V PP AC output signal that drives the EL lamp. The MIC8 is comprised of two stages: a boost stage, and an H-bridge, lamp driver, stage. The boost stage steps the input voltage up to +9V. The H-bridge stage then alternately switches the +9V output to each terminal of the EL lamp, thus creating a 18V PP AC signal to drive the EL lamp and generate light. The MIC8 features separate oscillators for the boost- and H-bridge stages. External resistors independently set the operating frequency of each stage. This flexibility allows the EL lamp circuit to be optimized for maximum efficiency and brightness. The MIC8 uses a single inductor and a minimum number of external components, making it ideal for portable, spacesensitive applications. The MIC8 is available in an 8-pin MSOP package with an ambient temperature range of C to +85 C. Features 1.8V to 5.5V DC input voltage 18V PP regulated AC output waveform Independently adjustable EL lamp frequency Independently adjustable boost converter frequency.1µa shutdown current Applications LCD panel backlight Cellular phones PDAs Pagers Calculators Remote controls Portable phones Ordering Information Part Number Ambient Standard Pb-Free Temp. Range Package MIC8BMM MIC8YMM C to +85 C MSOP-8 Typical Application C IN 1µF k.m µh 1 5 MIC8 VDD SW VA 8 1N18.µF/1V in EL LAMP TIME (ms/div) High Voltage EL Driver, Inc. 189 Fortune Drive San Jose, CA 9511 USA tel + 1 (8) 9-8 fax + 1 (8) January 5 1 MIC8

2 Pin Configuration VDD 1 8 VA 5 SW 8-Pin MSOP Package (MM) Pin Description Pin Number Pin Name Pin Function 1 VDD Supply (Input): 1.8V to 5.5V for internal circuitry. Switch Resistor (External Component): Set switch frequency of the internal power MOSFET by connecting an external resistor to VDD. Connecting the external resistor to disables the switch oscillator and shuts down the device. EL Resistor (External Component): Set EL frequency of the internal H-bridge driver by connecting an external resistor to VDD. Connecting the external resistor to disables the EL oscillator. Ground Return. 5 SW Switch Node (Input): Internal high-voltage power MOSFET drain. Regulated Boost Output (External Component): Connect to the output capacitor of the boost regulator and connect to the cathode of the diode. EL Output: Connect to one end of the EL lamp. Polarity is not important. 8 VA EL Output: Connect to the other end of the EL lamp. Polarity is not important. MIC8 January 5

3 Absolute Maximum Ratings (Note 1) Supply Voltage (V DD )....5V to V Output Voltage (V )....5V to 1V Frequency Control Voltage (V, V )....5V to (V DD +.V) Power T A = 85 C... mw Storage Temperature (T S )... 5 C to +15 C ESD Rating... Note Operating Ratings (Note ) Supply Voltage (V DD ) V to +5.5V Lamp Drive Frequency (f EL )... Hz to 1Hz Switching Transistor Frequency (f SW )... 8kHz to khz Ambient Temperature (T A )... C to +85 C Package Thermal Resistance MSOP (θ JA )... C/W Electrical Characteristics = V DD =.V, R SW = 5KΩ, R EL = 1.MΩ. T A = 5 C unless otherwise specified. Bold values indicate C T A +85 C Symbol Parameter Condition Min Typ Max Units R DS(ON) On-resistance of switching transistor I SW = 1 ma, V = 85V.8. Ω V Output voltage regulation V DD = 1.8V to 5.5V V 8 9 V Output peak-to-peak voltage V DD = 1.8V to 5.5V V 1 19 V V EN-L Input low voltage (turn-off) V DD = 1.8V to 5.5V.5 V V EN-H Input high voltage (turn-on) V DD = 1.8V to 5.5V V DD.5 V I SD Shutdown current, Note R SW = LOW; R EL = LOW;.1.1 µa V DD = 5.5V.5 µa I VDD Input supply current R SW = HIGH; R EL = HIGH; 1 5 µa V = 85V;, OPEN I Boosted supply current R SW = HIGH; R EL = HIGH; µa V = 85V;, OPEN I IN Input current including inductor = V DD = 1.8V 8 ma current (See Test Circuit) f EL output drive frequency 85 5 Hz f SW Switching transistor frequency 5 9 khz D Switching transistor duty cycle 9 % Note 1. Note. Note. Note. Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Devices are ESD sensitive. Handling precautions recommended. Shutdown current is defined as the sum of current going into pin 1, 5, and when the device is disabled. Test Circuit µh 1N18 C IN 1µF 1 5 VDD SW 5k.M 8 1Ω VA MIC8 1nF.µF/1V January 5 MIC8

4 Typical Characteristics INPUT CURRENT (ma) 5 R SW = k R EL = M Total Input Current vs. Input Voltage R SW = 5k R EL = 1M Lamp = in L = µh 1 =.1µF R SW = k D = BAVWS R EL =.M 1 5 INPUT VOLTAGE (V) INPUT CURRENT (ma) 5 Total Input Current vs. Temperature R SW = 5k R EL = 1M R SW = k R EL = M V IN =.V Lamp = in R 1 SW = k L = µh R =.M =.1µF EL D = BAVWS TEMPERATURE ( C) OUTPUT VOLTAGE (V P-P ) Output Voltage vs. Input Voltage R 18 SW = k 1 R = M EL 1 1 R SW = 5k 1 R = 1M EL 8 R SW = k R =.M Lamp = in EL L = µh =.1µF D = BAVWS 1 5 INPUT VOLTAGE (V) OUTPUT VOLTAGE (V PP ) Output Voltage vs. Temperature R SW = 5k R EL = 1M R SW = k R EL =.M R SW = k R EL = M =.V Lamp = in L = µh =.1µF D = BAVWS TEMPERATURE ( C) V (VG ) Voltage vs. Input Voltage R SW = k R EL = M R SW = k R EL =.M R SW = 5k R EL = 1M Lamp = in L = µh =.1µF 1 D = BAVWS 1 5 INPUT VOLTAGE (V) V (VG ) Voltage vs. Temperature R SW = 5k R EL = 1M R SW = k R EL = M R SW = k 5 R =.M =.V EL Lamp = in L = µh =.1µF D = BAVWS TEMPERATURE ( C) SWITCH RESISTANCE (Ω) 5 1 Switch Resistance vs. Input Voltage 1 5 INPUT VOLTAGE (V) SWITCHING FREQUENCY (khz) Switching Frequency vs. Switch Resistor SWITCH RESISTOR (kω) EL FREQUENCY (Hz) EL Frequency vs. EL Resistor EL RESISTOR (MΩ) SWITCHING FREQUENCY (Hz) Switching Frequency vs. Input Voltage R SW = k R SW = k R SW = 5k 1 5 INPUT VOLTAGE (V) EL FREQUENCY (Hz) EL Frequency vs. Input Voltage 5 R EL = 1M 5 R EL = M R EL =.M 1 5 INPUT VOLTAGE (V) FREQUENCY (KHz) Switching Frequency vs. Temperature R SW = k R SW = k R SW = 5k =.V TEMPERATURE ( C) MIC8 January 5

5 FREQUENCY (KHz) EL Frequency vs. Temperature R SW =.M R SW =1M R SW = M =.V TEMPERATURE ( C) OUTPUT VOLTAGE (V PP ) Output Voltage vs. Lamp Size 18 1 R SW = k 1 R EL =.M V IN =.V L =.1µF D = BAVWS 1 5 LAMP SIZE (sq. in.) INPUT CURRENT (ma) 5 15 Total Input Current vs. Lamp Size R SW = k R EL =.M 1 =.V L = µh 5 =.1µF D = BAVWS 1 5 LAMP SIZE (sq. in.) January 5 5 MIC8

6 Block Diagram µh 1 V DD C IN R SW 5 SW Switch Oscillator R EL Q 1 Q 8 VA V REF EL Oscillator EL LAMP /Q /Q Functional Description Overview The MIC8 is a high-voltage EL driver with an AC output voltage of 18V peak-to-peak capable of driving EL lamps up to in. Input supply current for the MIC8 is typically 1µA with a typical shutdown current of 1nA. The high voltage EL driver has two internal oscillators to control the switching MOSFET and the H-bridge driver. Both of the internal oscillators frequencies can be individually programmed through the external resistors to maximize the efficiency and the brightness of the lamps. Regulation Referring to Figure 1, initially power is applied to V DD. The internal feedback voltage is less than the reference voltage causing the internal comparator to go low which enables the switching MOSFET s oscillator. When the switching MOSFET turns on, current flows through the inductor and into the switch. The switching MOSFET will typically turn on for 9% of the switching frequency. During the on-time, energy is stored in the inductor. When the switching MOSFET turns off, current flowing into the inductor forces the voltage across the inductor to reverse polarity. The voltage across the inductor rises until the external diode conducts and clamps the voltage at V OUT +V. The energy in the inductor is then discharged into the capacitor. The internal comparator continues to turn the switching MOSFET on and off until the internal feedback voltage is above the reference voltage. Once the internal feedback voltage is above the reference voltage, the internal comparator turns off the switching MOSFET s oscillator. Figure 1. MIC8 Block Diagram When the EL oscillator is enabled, and switch in opposite states to achieve a 18V peak-to-peak AC output signal. The external resistor that connects to the pin determines the EL frequency. TIME (ms/div) MIC8 January 5 =.V L = µh =.µf Lamp = in R SW = k R EL = M Figure. 18Hz Typical Output Waveform Switching Frequency The switching frequency of the converter is controlled via an external resistor between pin and VDD pin of the device. The switching frequency increases as the resistor value decreases. For resistor value selections, see the Typical Characteristics: Switching Frequency vs. Switch Resistor or use the equation below. The switching frequency range is 8kHz to khz, with an accuracy of ±%. f SW(kHz) = R SW(M Ω)

7 EL Frequency The EL lamp frequency is controlled via an external resistor connected between pin and VDD pin of the device. The lamp frequency increases the resistor value decreases. For resistor value selections, see the Typical Characteristics: EL Frequency vs. EL Resistor or use the equation below. The switching frequency range is Hz to 1Hz, with an accuracy of ±%. f EL(Hz) = R EL(M Ω) In general, as the EL lamp frequency increases, the amount of current drawn from the battery will increase. The color of the EL lamp and the intensity are dependent upon its frequency. =.V L = µh =.µf Lamp = in R SW = 5k R EL = 1M TIME (ms/div) TIME (ms/div) Figure. 18Hz Output Waveform Figure. Hz Output Waveform Enable Function The enable function of the MIC8 is implemented by switching the R SW and R EL resistor between ground and V DD. When R SW and R EL are connected to ground, the switch and the EL oscillators are disabled; therefore the EL driver becomes disabled. When these resistors connect to V DD, both the oscillators will function and the EL driver is enabled. January 5 MIC8

8 Application Information Inductor In general, smaller value inductors, which can handle more current, are more suitable to drive larger size lamps. As the inductor value decreases, the switching frequency (controlled by R SW ) should be increased to avoid saturation or the input voltage should be increased. Typically, inductor values ranging from µh to 5µH can be used. offers the LQHC series up to 5µH and LQHC series up to µh, with low DC resistance. A µh (LQHC1K) inductor is recommended for driving a lamp size of square inches. It has a maximum DC resistance of.ω. Pre-designed Application Circuit Li-Ion Battery.V to.v µh Vishay Telefunken LQHC1K MC8 Diode The application circuit specifies the 1N18 or equivalent. It has a forward current of 15mA and a typical forward voltage of 95mV. For applications that are not cost driven, a fastswitching diode with lower forward voltage and higher reverse voltage can be used to enhance the efficiency, such as BAVWS or BASW. Output Capacitor Low ESR capacitors should be used at the regulated boost output ( pin) of the MIC8 to minimize the switching output ripple voltage. Selection of the capacitor value will depend upon the peak inductor current, inductor size, and the load. MuRata offers the GRM- series with up to.µf at 1V, with a XR temperature coefficient in 1 surfacemount package. Typically, values ranging from.1µf to.1µf at 1V can be used for the regulated boost output capacitor. C 1µF/.V GRM-X5R1K. C1.µF/1V GRM9XR K1 R.M R1 k 1 5 VDD MIC8 SW VA 8.1µF/1V GRMXR1K in LAMP I IN F EL Lamp Size.V 8mA 18V PP 1Hz in TIME (ms/div) Figure 5. Typical 1Hz EL Driver for in Lamp MIC8 8 January 5

9 I IN F EL Lamp Size.V 18mA 18V PP 1Hz in January 5 9 MIC8

10 .V to 5.5V 5k LQCN51K1 Diodes BASW C 1µF/.V GRM-X5R1K. R.M R1 5k 1 5 VDD MIC8 SW VA 8.µF/1V GRM-XR1K1 EL LAMP LSI X5-1 I IN F EL Lamp Size.V 1mA 18V PP 1Hz in TIME (ms/div) Figure. Typical EL Driver for in Lamp with 5µH inductor MIC8 1 January 5

11 1.5V V DD 1.8V to 5.5V C1.1µF/5V GRM-X5R1K. C 1µF/.V GRM-X5R1K. R1 5k R.M µh LQHC1K 1 5 MIC8 VDD SW VA 8 Diodes BASW.1µF/1V GRM-XR1K1 EL LAMP I IN V DD I DD F EL Lamp Size 1.5V ma.v µa 18V PP 1Hz 1.in TIME (ms/div) Figure 8. Typical Split Power Supplies Applications January 5 11 MIC8

12 1.8V to.v (X Alkaline Batteries) µh LQCN51K1 Diodes BASW C 1µF/.V GRM-X5R1K. R.M R1 1M 1 5 VDD MIC8 SW VA 8.1µF/1V GRM-XR1K1 EL LAMP Elite 1-N I IN F EL Lamp Size.V 1mA 18V PP 1Hz 5.in TIME (ms/div) Figure 9. Typical EL Driver for Remote Control Lamp (Blue Phosphor) Applications MIC8 1 January 5

13 Package Information.1 (.1).11 (.8).199 (5.5).18 (.) DIMENSIONS: INCH (MM). (.9). (.81).1 (.5).11 (.95). (1.9).8 (.9).1 (.) R. (.18).5 (.1).1 (.).5 (.5) TYP.8 (.). (.1) 5 MAX MIN 8-Lead MSOP (MM).1 (.) R.9 (.99).5 (.89).1 (.5) MIC INC. 189 FORTUNE DRIVE SAN JOSE, CA 9511 USA TEL + 1 (8) 9-8 FAX + 1 (8) 9-9 WEB This information is believed to be accurate and reliable, however no responsibility is assumed by 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 Inc. 5 Incorporated January 5 1 MIC8