MIC4834 Low Noise Dual 220 VPP EL Driver General Description Features The MIC4834 is a low noise dual Electroluminescent (EL) Panel driver used in backlighting applications. The MIC4834 converts a low DC voltage to a high DC voltage using a boost converter and then alternates the high DC voltage across the EL panels using an H-bridge. The MIC4834 incorporates internal wave-shaping circuitry specifically designed to reduce audible noise emitted by EL panels. With only one inductor the MIC4834 can drive two outputs and requires a minimum number of passive components. It features an operating input voltage range of 2.3V to 5.8V, making it suitable for 1-cell Li-ion and 2- or 3-cell alkaline/NiCad/NiMH battery applications. The MIC4834 features separate oscillators for the boost and H-bridge stages. The boost frequency may be adjusted with an external resistor to optimize efficiency and brightness. The H-bridge frequency is internally preset to 225Hz, to reduce the number of external components and layout space. The MIC4834 is available in 10 pin 3mmx3mm MLF® package as well as MSOP-10L, and has an operating junction temperature range of –40°C to +125°C. • • • • • • • • • Drives two EL panels, up to 3 in2 each at full brightness 220VPP regulated AC output waveform 2.3V to 5.8V DC input voltage Wave-shaping circuit to reduce audible noise Adjustable boost converter frequency Single inductor to power both panels 0.1µA typical shutdown current Package options − 10-pin 3mmx3mm MLF® − 10-pin MSOP –40oC to +125oC junction temperature range Applications • • • • • • • Mobile phones MP3/portable media players (PMP) Clocks/ watches Remote controls Cordless phones GPS devices PDAs _________________________________________________________________________________________________ Typical Application Low Noise Dual EL Driver MLF and MicroLead Frame are registered trademark of Amkor Technologies Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com October 2008 M9999-100808-A Micrel MIC4834 Ordering Information Part Number Package Operating Junction Temp Range Lead Finish MIC4834YML 10 pin (3mm x 3mm) MLF® -40ºC to +125ºC Pb-free / RoHS-Compliant MIC4834YMM 10-Pin MSOP -40ºC to +125ºC Pb-free / RoHS-Compliant Pin Configuration ® 10-Pin MLF - Top View 10-Pin MSOP – Top View Pin Description Pin Number Pin Name Pin Function 1 ENA EL Panel A Enable Pin: Logic high enables ELA and logic low disables ELA output. 2 VDD DC Input Supply Voltage: 2.3V to 5.8V 3 RSW RSW pin: Sets internal boost converter switch frequency by connecting an external resistor (RSW) to VDD. Connecting the RSW resistor to GND shuts down the device. 4 ENB EL Panel B enable pin: Logic high enables ELB and logic low disables ELB output. 5 GND Ground. 6 SW Switch Node: Drain of internal high-voltage power MOSFET for boost circuit. 7 CS Regulated Boost Output: Connect to the output capacitor of the boost regulator and to the cathode of the diode. 8 COM EL output: Common EL output terminal to both ELA and ELB. Connect one end of each EL panel to this pin. 9 ELB EL Panel B output: Connect the other end of the EL panel B to this pin. 10 ELA EL Panel A output: Connect the other end of the EL panel A to this pin. EPad HS Pad October 2008 Heat Sink Pad. Connect to ground externally. MLF® package only. 2 M9999-100908-A Micrel MIC4834 Absolute Maximum Rating(1) Operating Range(2) Supply voltage (VDD) ....................................... -0.5V to 6.5V Output voltage (VCS)...................................... -0.5V to 130V Switch Node (VSW) ......................................... -0.5V to 130V Enable Voltage (VRSW, VENA, VENB)................... -0.5V to 6.5V Ambient Storage Temperature (TS) ........... -65ºC to +150ºC ESD Rating(3) ........................................................................... ESD Sensitive Supply Voltage (VDD) ........................................2.3V to 5.8V Switching MOSFET Frequency (fSW) ........ 35kHz to 350kHz Enable Voltage (VRSW, VENA,, VENB) ....................... 0V to VDD Junction Temperature Range (TJ) ............. -40°C to +125°C Package Thermal Impedance 3mm x 3mm MLF® (θJA)……………………........ 60°C/W MSOP (θJA)……………………......................... 206°C/W Electrical Characteristics(4) TA = 25oC, VDD= 3.0V unless otherwise noted. Bold values indicate -40°C ≤ TJ ≤ 85°C. Symbol Parameter VDD Supply Voltage Range IDD Input Supply Current VRSW = High; VCS = 105V; ELA, ELB, COM = Open ISD Shutdown Current RDS(ON) VCS fSw Max Units 5.8 V 152 220 µA VRSW = Low; VDD = 5.8V 0.1 1 µA On-resistance Of Switching Transistor ISW = 100mA, VCS = 105V 6.0 12.0 Ω Output voltage Regulation VDD = 2.3V to 5.8v 90 109 120 V VDD = 3.0V (RSW = 1.3MΩ ) 25 35 45 kHz VDD = 3.0V (RSW = 450kΩ) 75 100 125 kHz VDD = 3.0V (RSW = 125kΩ) 250 350 450 kHz VDD = 3.0V ELA, ELB, COM = Open 165 225 285 Hz 95 % 7.5 mA 1.2 V 50 150 mV 0.1 1 µA Boost Switching Frequency Condition Min Typ 2.3 fEL ELA, ELB and COM Drive Frequency D Switching Transistor Duty Cycle 80 IOUT Output Current Drive Limit 2.5 VENA, VENB Enable Logic Threshold 0.4 VHYS Enable Logic Hysteresis 20 IENA, IENB Enable Input Current 5 Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF. 4. Specification for packaged product only. October 2008 3 M9999-100908-A Micrel MIC4834 Recommended Switching Frequency Vs. Total Lamp Size 300 250 200 150 100 50 C = 2.2nF 30 f = 94kHz 25 Size = 2in2 100 80 60 40 20 EL = 225Hz OUT SW 20 15 10 5 f SW = 116kHz 2 OUT 50 1400 fSW = 62kHz 45 2 Size = 4in 40 35 f SW 90 85 = 225Hz = 2.2nF = 82kHz 2 3 4 5 6 OUT f = 2.2nF = 42kHz SW 2 Size = 6in 65 60 55 50 f = 50kHz SW 45 Size = 5in2 40 2 2.5 3 3.5 4 4.5 5 5.5 6 INPUT VOLTAGE (V) 16 240 120 fEL = 225Hz C 80 75 70 Output Voltage vs. Input Voltage 100 80 60 40 f SW = 45kHz 20 fEL = 225Hz COUT = 2.2nF 0 2 2.5 3 3.5 4 4.5 5 5.5 6 INPUT VOLTAGE (V) Brightness vs. Input Voltage 14 160 120 SW = 45kHz 40 fEL = 225Hz C = 2.2nF OUT 0 2 2.5 3 3.5 4 4.5 5 5.5 6 INPUT VOLTAGE (V) October 2008 BRIGHTNESS (lux) 200 80 f 1 CS VOLTAGE (V) EL C 1200 800 f 55 1000 600 CS Voltage vs. Input Voltage 400 Total Input Current vs. Input Voltage 200 Total Input Current vs. Input Voltage 0 0 2 Size = 3in2 20 2 2.5 3 3.5 4 4.5 5 5.5 6 INPUT VOLTAGE (V) OUTPUT VOLTAGE (VP-P) f TOTAL LAMP SIZE (in ) INPUT CURRENT (mA) INPUT CURRENT (mA) 35 SWITCHING RESISTOR (kOhm) 60 25 40 120 Size = 1in 0 2 2.5 3 3.5 4 4.5 5 5.5 6 INPUT VOLTAGE (V) 0 30 Total Input Current vs. Input Voltage 140 INPUT CURRENT (mA) 350 SWITCHING FREQUENCY (kHz) Switching Frequency vs SW Resistor 400 0 SWITCHING FREQUENCY (kHz) Typical Characteristics 12 10 8 6 Distance = 2 in fSW = 135kHz 4 f 2 EL = 225Hz L = 220µH 0 2 2.5 3 3.5 4 4.5 5 5.5 6 INPUT VOLTAGE (V) 4 M9999-100908-A Micrel MIC4834 Functional Diagram Figure 1. MIC4834 Block Diagram Functional Description programmed through an external resistor to maximize efficiency and brightness of the EL panel. The H-bridge frequency is internally fixed at 225Hz to reduce external component count. Overview The MIC4834 is a high-voltage dual output EL driver with a peak-to-peak AC output voltage of 220V capable of driving two 3 in2 EL panels. The MIC4834 drives EL panels by converting a low DC input voltage to a high DC high output voltage using the boost regulator circuit and then alternating the high DC voltage across the EL panel using an H-Bridge. Input supply current for the MIC4834 is typically 152µA. The high voltage EL driver has two internal oscillators to control the boost switching frequency and the H-bridge driver frequency. The internal boost oscillator frequency can be individually October 2008 Regulation Referring to Figure 1, power is initially applied to VDD. When the internal feedback voltage is less than the reference voltage, the internal comparator enables switching in the boost circuit. When the boost regulator is switching, current flows through the inductor into the switch. The switching MOSFET will typically turn on for 90% of the switching period. During the on-time, energy 5 M9999-100908-A Micrel MIC4834 ENA or ENB high (over 1.2V) or low (below 0.4V) will turn ELA and ELB panels on or off. 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 disables switching. The control circuit will continue to turn the MOSFET’s on and off to maintain a constant DC voltage at the CS pin. When the MIC4834 EL Driver is enabled, ELA and ELB will switch in opposite states with COM to achieve a 220V peak-to-peak AC output signal needed to drive the two EL panels. Figure 2. EL Panel Waveform – 2 × 1 in2 Switching Frequency The switching frequency of the converter is controlled by an external resistor (RSW) between RSW and VDD. The switching frequency increases as the resistor value decreases. In general, the lower the switching frequency, the greater the input current is drawn to deliver more power to the output. Lowering the switching frequency can be used to drive larger panels. However, the switching frequency should not be so low as to allow the voltage at the switch node or the CS pin to exceed the absolute maximum voltage of those pins. For resistor value selections, see the “Typical Characteristics: Switching Frequency vs. SW Resistor” graph on Page 4 or use the equation below. The switching frequency range is 35kHz to 350kHz, with an accuracy of ±20%. fSW (kHz) = 2 Figure 3. EL Panel Waveform – 2 × 2 in 46 R SW (MΩ ) EL Frequency The MIC4834 EL panel frequency is internally fixed at 225Hz. Enable Function There are a few different ways to enable and disable the MIC4834. The boost regulator may be disabled by pulling the RSW resistor to ground. This turns off both the EL panels by cutting power to the device completely. The RSW resistor must be pulled to VDD to enable the boost oscillator. If it is not equal to VDD, then the frequency set by RSW will be different the programmed value. For individual panel control, the ENA and ENB pins can be used to enable ELA and ELB, respectively. Pulling October 2008 Figure 4. EL Panel Waveform – 2 × 3 in2 6 M9999-100908-A Micrel MIC4834 Output Capacitor Low ESR capacitors should be used at the regulated boost output (CS pin), to minimize the switching output ripple voltage. The larger the output capacitance, the lower the output ripple at the CS pin. The reduced output ripple, at the CS pin, along with a low ESR capacitor improves the efficiency of the MIC4834 circuit. Selection of the capacitor value depends upon the peak inductor current, inductor size, and the load. The MIC4834 is designed for use with an output capacitance as low as 2.2nF. For minimum audible noise, the use of a C0G/NPO dielectric output capacitor is recommended. TDK and AVX offer C0G/NPO dielectric capacitors in capacitance up to 2.7nF at 200V to 250V voltage rating in 0805 size. Application Information The MIC4834 is designed to use an inductance with a value between 100µH to 330µH. Choosing the right inductor is always a balance of size, inductance, efficiency, current rating and cost. A TDK (VLS4012T221M) 220µH inductor is recommended based on size, efficiency and current rating. Generally, the lower the inductance, the more current the inductor can handle. Lowering the inductance allows the boost regulator to draw more input current to deliver more energy every switching cycle. As a result, a lower inductance may be used to drive larger panels or brighten similar sized panels. However, caution is required as using a low inductance with a low switching frequency may cause the voltage at the switch node and the CS pin to exceed the absolute maximum rating. If the application uses a low input voltage (2.3V to 3V), then a lower value inductor, such as 100µH, may be used in order to drive the EL panel at maximum brightness. EL Panel Terminals (ELA, ELB, COM) The two EL panels are connected from ELA to COM and ELB to COM. The ELA and ELB terminals are in phase with each other, while the COM is out of phase with both ELA and ELB. Since ELA and COM are out of phase, the high voltage generated by the boost regulator is alternated across ELA and COM by the H-Bridge. The frequency of each cycle is internally fixed at 225Hz. The alternating 220V peak-to-peak causes the EL panel to emit light. Similarly, the ELB and COM are also out of phase and allows a second EL panel to be driven at the same time. Both EL panels may operate independently from each other and do not have to be the same size. For component selection, Table 2 lists recommended values for various panel sizes up to a total of 6 in2 (For example, two 3 in2 panels). Driving overly large panels will result in a dimmer display, but will not cause damage to the device. Diode The diode must have a high reverse voltage (150V), since the output voltage at the CS pin can reach up to 130V. A fast switching diode with lower forward voltage and higher reverse voltage (150V), such as BAV20WS/BAS20W, can be used to enhance efficiency. October 2008 7 M9999-100908-A Micrel MIC4834 Application Circuit Figure 6. Typical Li-Ion Powered MIC4834 Circuit Note: Table 2 applies to circuit shown in Figure 6. Total Panel Area (in2) 0.4 1 2 3 4 5 6 Capacitance (nF) 2 5 10 15 20 25 30 RSW (kΩ) 357 392 487 562 750 931 1100 fSW (kHz) 128 116 94 82 62 50 42 Table 2. Recommended RSW Values for Total Panel Sizes Bill of Materials Item Part Number C1 C1608X7R1A103K TDK(1) C1608X5R0J106K C2 C3 C2012C0G2E2222J L1 VLS4012T-221M D1 BAS20-V-GS18 R1 or RSW U1 CRCW06033323FKEYE3 MIC4834YML Manufacturer Description Qty 0.01µF Ceramic Capacitor, 10V, X7R, Size 0603 1 TDK (1) 10 µF Ceramic Capacitor, 6.3V, X5R, Size 0603 1 TDK (1) 0.0022µF Ceramic Capacitor, 250V, C0G, Size 0805 1 TDK (1) 220µH, 210mA ISAT. (4mmx4mmx1.2mm) 1 200V/200mA Hi-Voltage Switching Diode 1 (2) 332kΩ, 1%, 1/16W, Size 0603 1 (3) Low Noise Dual 220Vp-p EL Driver with Output Slew Control 1 Vishay(2) Vishay Micrel Notes: 1. TDK: www.tdk.com 2. Vishay: www.vishay.com 3. Micrel, Inc.: www.micrel.com October 2008 8 M9999-100908-A Micrel MIC4834 Layout Recommendation (MLF®) Top Layer Bottom Layer October 2008 9 M9999-100908-A Micrel MIC4834 Layout Recommendation (MSOP) Top Layer Bottom Layer October 2008 10 M9999-100908-A Micrel MIC4834 Package Information 10-Pin 3mm x 3mm MLF® (ML) October 2008 11 M9999-100908-A Micrel MIC4834 10-Pin MSOP (MM) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2008 Micrel, Incorporated. October 2008 12 M9999-100908-A