MIC4826 Micrel MIC4826 Low Input Voltage, 160VPP Output Voltage, EL Driver Final Information General Description Features Micrel’s MIC4826 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 2- or 3-cell alkaline/NiCad/NiMH battery applications. The MIC4826 converts a low voltage DC input to a 160VPP AC output signal that drives the EL lamp. The MIC4826 is comprised of two stages: a boost stage, and an H-bridge, lamp driver, stage. The boost stage steps the input voltage up to +80V. The H-bridge stage then alternately switches the +80V output to each terminal of the EL lamp, thus creating a 160VPP AC signal to drive the EL lamp and generate light. The MIC4826 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 MIC4826 uses a single inductor and a minimum number of external components, making it ideal for portable, spacesensitive applications. The MIC4826 is available in an 8-pin MSOP package with an ambient temperature range of –40°C to +85°C. • • • • • 1.8V to 5.5V DC input voltage 160VPP regulated AC output waveform Independently adjustable EL lamp frequency Independently adjustable boost converter frequency 0.1µA shutdown current Applications • • • • • • • LCD panel backlight Cellular phones PDAs Pagers Calculators Remote controls Portable phones Ordering Information Part Number Standard Pb-Free Temp. Range Package MIC4826BMM MIC4826YMM –40°C to +85°C MSOP-8 Typical Application 1 VDD SW 5 442k 2 RSW CS 6 2M 3 REL VA 8 4 GND VB 7 VB (50V/div) COUT 0.01µF/100V MIC4826 VA — VB (50V/div) CIN 10µF D1 1N4148 VA (50V/div) L1 220µH VIN 2in2 EL LAMP TIME (2ms/div) High Voltage EL Driver Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000• http://www.micrel.com August 2004 1 MIC4826 MIC4826 Micrel Pin Configuration VDD 1 8 VA RSW 2 7 VB REL 3 6 CS GND 4 5 SW 8-Pin MSOP Package (MM) Pin Description Pin Number Pin Name 1 VDD Supply (Input): 1.8V to 5.5V for internal circuitry. 2 RSW Switch Resistor (External Component): Set switch frequency of the internal power MOSFET by connecting an external resistor to VDD. Connecting the external resistor to GND disables the switch oscillator and shutdown the device. 3 REL 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 GND disables the EL oscillator. 4 GND Ground Return. 5 SW Switch Node (Input): Internal high-voltage power MOSFET drain. 6 CS Regulated Boost Output (External Component): Connect to the output capacitor of the boost regulator and connect to the cathode of the diode. 7 VB 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. MIC4826 Pin Function 2 August 2004 MIC4826 Micrel Absolute Maximum Rating (Note 1) Operating Ratings (Note 2) Supply Voltage (VDD) ..................................... –0.5V to +6V Output Voltage (VCS) ................................. –0.5V to +100V Frequency Control Voltage (VRSW, VREL) ... –0.5V to (VDD + 0.3V) Power Dissipation @ TA = 85°C ............................. 200mW Storage Temperature (TS) ....................... –65°C to +150°C ESD Rating .............................................................. Note 3 Supply Voltage (VDD) ...................................... 1.8V to 5.5V Lamp Drive Frequency (fEL) ...................... 60Hz to 1000Hz Switching Transistor Frequency (fSW) ........ 8kHz to 200kHz Ambient Temperature (TA) ......................... –40°C to +85°C Package Thermal Resistance 8-pin MSOP (θJA) .............................................. 206°C/W Electrical Characteristics VIN = VDD = 3.0V, RSW = 560KΩ, REL = 1.0MΩ. TA = 25°C unless otherwise specified. Bold values indicate -40°C ≤ TA ≤ +85°C Symbol Parameter Condition Min RDS(ON) On-resistance of switching transistor ISW = 100 mA, VCS = 75V VCS Output voltage regulation VDD = 1.8V to 5.5V 75 Typ Max Units 3.8 7.0 Ω 80 85 V 87 V 170 V 174 V 0.5 V 73 VA – VB Output peak-to-peak voltage VDD = 1.8V to 5.5V 150 160 146 VEN-L Input low voltage (turn off) VDD = 1.8V to 5.5V VEN-H Input high voltage (turn on) VDD = 1.8V to 5.5V ISD Shutdown current, Note 4 RSW = LOW; REL = LOW; VDD–0.5 V 0.01 VDD = 5.5V 0.1 µA 0.5 µA IVDD Input supply current RSW = HIGH; REL = HIGH; VCS = 75V; VA, VB OPEN 21 75 µA ICS Boosted supply current RSW = HIGH; REL = HIGH; VCS = 75V; VA, VB OPEN 200 400 µA IIN Input current including inductor current VIN = VDD = 1.8V (See Test Circuit) 28 fEL VA–VB output drive frequency 285 360 435 Hz fSW Switching transistor frequency 53 66 79 kHz D Switching transistor duty cycle 90 Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Note 4. Shutdown current is defined as the sum of current going into pin 1, 5, and 6 when the device is disabled. mA % Test Circuit L1 220µH VIN COUT 0.01µF/100V MIC4826 CIN 10µF 442k 2M August 2004 D1 1N4148 1 VDD SW 5 2 RSW CS 6 3 REL VA 8 4 GND VB 7 3 100Ω 10nF MIC4826 MIC4826 Micrel Typical Characteristics Total Input Current vs. Input Voltage Total Input Current vs. Temperature 50 = 562k, R EL = 1M RSW = 442k 15 10 5 0 0 = 2M RSW = 332k REL = 3.32M Lamp = 2in2 L = 220µH D = BAV19WS C = 0.1µF OUT 1 2 3 4 5 INPUT VOLTAGE (V) 6 25 20 VIN = 3.0V 15 Lamp = 2in2 10 R = 332k SW L = 220µH D = BAV19WS 5 REL = 3.32M COUT = 0.1µF 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Output Voltage vs. Temperature VCS (VAVG) OUTPUT VOLTAGE (VPP) 70 60 50 40 20 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 10 0 1 Switch Resistance vs. Input Voltage SWITCHING FREQUENCY (kHz) SWITCH RESISTANCE (Ω) 6 5 4 3 2 1 0 1 2 3 4 5 INPUT VOLTAGE (V) 6 EL FREQUENCY (Hz) SWITCHING FREQUENCY (Hz) RSW = 442k RSW = 562k 20 Lamp = 2in2 L = 220µH COUT = 0.1µF D = BAV19WS 1000 100 10 0.1 1000 10000 SWITCH RESISTOR (kΩ) 1 EL RESISTOR (MΩ) 10 Switching Frequency vs. Temperature 120 300 REL = 1M 250 REL = 2M 200 150 100 0 1 VIN = 3.0V 10000 REL = 3.32M 50 6 REL = 1M RSW = 442k REL = 2M EL Frequency vs. EL Resistor 350 RSW = 332k 2 3 4 5 INPUT VOLTAGE (V) SW EL Frequency vs. Input Voltage 40 MIC4826 6 10 1 100 6 10 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 400 60 0 1 2 3 4 5 INPUT VOLTAGE (V) 70 R = 332k SW 60 REL = 3.32M 50 40 R = 562k 30 20 Lamp = 2in2 L = 220µH COUT = 0.1µF D = BAV19WS 100 Switching Frequency vs. Input Voltage 80 RSW = 332k REL = 3.32M 1000 120 100 RSW = 562k REL = 1M Switching Frequency vs. Switch Resistor 7 OUT 2 3 4 5 INPUT VOLTAGE (V) 90 80 30 20 Lamp = 2in2 L = 220µH COUT = 0.1µF D = BAV19WS Lamp = 2in2 L = 220µH D = BAV19WS C = 0.1µF 100 R =442k 90 SW REL = 2M 80 140 R = 332k RSW = 442k SW 120 R = 3.32M REL = 2M EL 100 RSW = 562k 80 VIN = 3.0V REL = 1M 60 40 60 40 CS Voltage vs. Temperature 100 180 160 RSW = 562k REL = 1M 100 R = 332k SW 80 REL = 3.32M CS Voltage vs. Input Voltage 200 = 442k 140 120 20 0 1 VCS (VAVG) 25 20 EL RSW = 442k REL = 2M 35 30 R 180 RSW= 2M EL 160 EL FREQUENCY (Hz) R 200 R = 562k 45 SW REL = 1M 40 FREQUENCY (KHz) 35 30 SW VA –VB (VPP) R 45 40 INPUT CURRENT (mA) INPUT CURRENT (mA) 50 Output Voltage vs. Input Voltage 2 3 4 5 INPUT VOLTAGE (V) 4 100 80 60 RSW = 332k RSW = 442k RSW = 562k 40 20 VIN = 3.0V 6 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) August 2004 MIC4826 Micrel EL Frequency vs. Temperature Output Voltage vs. Lamp Size 250 RSW = 2M 200 150 100 50 RSW = 3.32M VIN = 3.0V 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) August 2004 20 160 140 120 INPUT CURRENT (mA) 300 RSW =1M OUTPUT VOLTAGE (VPP) FREQUENCY (KHz) 350 Total Input Current vs. Lamp Size 180 400 RSW = 332k REL = 3.32M 100 80 60 VIN = 3.0V L = 220µH COUT = 0.1µF D = BAV19WS 40 20 0 0 1 2 3 4 5 6 LAMP SIZE (sq. in.) 5 7 18 16 RSW = 332k REL = 3.32M 14 12 10 8 VIN = 3.0V L = 220µH D = BAV19WS COUT = 0.1µF 6 4 2 0 0 1 2 3 4 5 6 LAMP SIZE (sq. in.) 7 MIC4826 MIC4826 Micrel Functional Diagram L1 220µH VIN 1 D1 VDD 5 RSW CIN SW 2 RWS Switch Oscillator COUT 6 CS Q1 8 REL VA Q2 EL Oscillator VREF EL LAMP Q3 7 VB 3 Q4 REL 4 GND Figure 1. MIC4826 Block Diagram When the EL oscillator is enabled, VA and VB switch in opposite states to achieve a 160V peak-to-peak AC output signal. The external resistor that connects to the REL pin determines the EL frequency. Functional Description MIC4826 VA (50V/div) See “Application Information” for component selection and pre-designed circuits. Overview The MIC4826 is a high voltage EL driver with an AC output voltage of 160V peak-to-peak capable of driving EL lamps up to 6 in2 . Input supply current for the MIC4826 is typically 21µA with a typical shutdown current of 10nA. 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 VDD. 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 90% 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 VOUT+VD1. The energy in the inductor is then discharged into the COUT 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. VA — VB (50V/div) VB (50V/div) VIN = 3.0V L = 220µH COUT = 0.01µF Lamp = 2in2 RSW = 332k REL = 3.32M TIME (2ms/div) Figure 2. 108Hz Typical Output Waveform Switching Frequency The switching frequency of the converter is controlled via an external resistor between RSW pin and VDD pin of the device. The switching frequency increases as the resistor value decreases. For resistor value selections, see “Typical Characteristics: Switching Frequency vs. Switch Resistor” or use the equation below. The switching frequency range is 8kHz to 200kHz, with an accuracy of ±20%. fSW (kHz) = 6 36 RSW (MΩ) August 2004 MIC4826 Micrel VA — VB (50V/div) VIN = 3.0V L = 220µH COUT = 0.01µF Lamp = 2in2 RSW = 442k REL = 2M VB (50V/div) VIN = 3.0V L = 220µH COUT = 0.01µF Lamp = 2in2 RSW = 562k REL = 1M VB (50V/div) 360 REL (MΩ) VA (50V/div) fEL (Hz) = 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. VA (50V/div) EL Frequency The EL lamp frequency is controlled via an external resistor connected between REL pin and VDD pin of the device. As 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 EL frequency range is 60Hz to 1000Hz, with an accuracy of ±20%. TIME (2ms/div) Figure 4. 360Hz Output Waveform VA — VB (50V/div) Enable Function The enable function of the MIC4826 is implemented by switching the RSW and REL resistor between ground and VDD. When RSW and REL are connected to ground, the switch and the EL oscillators are disabled; therefore the EL driver becomes disabled. When these resistors connect to VDD, both oscillators will function and the EL driver is enabled. TIME (2ms/div) Figure 3. 180Hz Output Waveform August 2004 7 MIC4826 MIC4826 Micrel Diode The application circuit specifies the 1N4148 or equivalent. It has a forward current of 150mA and a typical forward voltage of 950mV. For applications that are not cost driven, a fast switching diode with lower forward voltage and higher reverse voltage can be used to enhance the efficiency, such as BAV19WS and BAV20WS. Output Capacitor Low ESR capacitors should be used at the regulated boost output (CS pin) of the MIC4826 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 GRM40 series with up to 0.015µF at 100V, with a X7R temperature coefficient in 0805 surfacemount package. Typically, values ranging from 0.01µF to 0.1µF at 100V can be used for the regulated boost output capacitor. 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 RSW) should be increased to avoid saturation or the input voltage should be increased. Typically, inductor values ranging from 220µH to 560µH can be used. Murata offers the LQH3C series up to 560µH and LQH4C series up to 470µH, with low DC resistance. A 220µH Murata (LQH4C221K04) inductor is recommended for driving a lamp size of 3 square inches. It has a maximum DC resistance of 4.0Ω. Pre-designed Application Circuits L1 D1 220µH Vishay Telefunken Murata MCL4148 LQH4C221K04 Li-Ion Battery VIN 3.0V to 4.2V C2 10µF/6.3V Murata GRM42-6X5R106K6.3 COUT 0.01µF/100V GRM40X7R103K MIC4826 C1 0.22µF/10V Murata GRM39X7R 224K10 R2 3.32M R1 322k 1 VDD SW 5 2 RSW CS 6 3 REL VB 7 4 GND VA 8 3in2 LAMP IIN VA–VB FEL Lamp Size 3.3V 20mA 160VPP 100Hz 3in2 VA — VB (50V/div) VB (50V/div) VA (50V/div) VIN TIME (2ms/div) Figure 5. Typical 100Hz EL Driver for 3in2 Lamp MIC4826 8 August 2004 MIC4826 Micrel L1 220µH Murata LQH4C221K04 VIN 2.5V to 5.5V C2 10µF/6.3V Murata GRM42-6X5R106K6.3 D1 Diodes BAV20WS COUT 0.1µF/100V GRM42-2X7R104K100 MIC4826 R1 R2 3.32M 332k 1 VDD SW 5 2 RSW CS 6 3 REL VB 7 4 GND VA 8 EL LAMP LSI X533-13 IIN VA–VB FEL Lamp Size 3.3V 14mA 160VPP 100Hz 2in2 VA — VB (50V/div) VB (50V/div) VA (50V/div) VIN TIME (2ms/div) Figure 6. Typical EL Driver for 2in2 Lamp with CS = 0.1µF August 2004 9 MIC4826 MIC4826 Micrel L1 560µH Murata LQ32CN561K21 VIN 3.3V to 5.5V C2 10µF/6.3V Murata GRM42-6X5R106K6.3 D1 Diodes BAV20WS COUT 0.01µF/100V GRM40X7R103K100 MIC4826 R2 3.32M R1 332k 1 VDD SW 5 2 RSW CS 6 3 REL VB 7 4 GND VA 8 EL LAMP LSI X533-13 IIN VA–VB FEL Lamp Size 3.3V 13.2mA 160VPP 100Hz 2in2 VA — VB (50V/div) VB (50V/div) VA (50V/div) VIN TIME (2ms/div) Figure 7. Typcial EL Driver for 2in2 Lamp with 560µH inductor MIC4826 10 August 2004 MIC4826 Micrel L1 220µH Murata LQH4C221K04 VIN 1.5V C2 10µF/6.3V Murata GRM42-6X5R106K6.3 VDD 1.8V to 5.5V R1 C1 0.01µF/50V Murata GRM40-X7R103K50 442k R2 3.32M D1 Diodes BAV20WS COUT 0.01µF/100V GRM40X7R103K100 MIC4826 1 VDD SW 5 2 RSW CS 6 3 REL VB 7 4 GND VA 8 EL LAMP IIN VDD IDD VA–VB FEL Lamp Size 1.5V 22mA 3.0V 36µA 160VPP 100Hz 1.6in2 VA — VB (50V/div) VB (50V/div) VA (50V/div) VIN TIME (2ms/div) Figure 8. Typical Split Power Supplies Applications August 2004 11 MIC4826 MIC4826 Micrel Package Information 0.199 (5.05) 0.187 (4.74) 0.122 (3.10) 0.112 (2.84) DIMENSIONS: INCH (MM) 0.120 (3.05) 0.116 (2.95) 0.036 (0.90) 0.032 (0.81) 0.043 (1.09) 0.038 (0.97) 0.012 (0.30) R 0.012 (0.3) 0.0256 (0.65) TYP 0.008 (0.20) 0.004 (0.10) 5° MAX 0° MIN 0.007 (0.18) 0.005 (0.13) 0.012 (0.03) R 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) 8-Lead MSOP (MM) MICREL INC. 1849 FORTUNE DRIVE TEL + 1 (408) 944-0800 FAX SAN JOSE, CA 95131 + 1 (408) 474-1000 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. © 2004 Micrel Incorporated MIC4826 12 August 2004