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MIC4832
Low Noise 220Vp-p EL Driver
General Description
The MIC4832 is a low noise 220Vp-p electroluminescent lamp (EL) driver. Using advanced Bipolar, CMOS, DMOS (BCD) technology, the MIC4832 integrates a high voltage boost converter and an H-bridge driver for driving a large EL lamp. The MIC4832 can drive large panel displays for mobile phones, multimedia players or automotive electronics where EL panels are used for backlighting. The MIC4832 offers design flexibility with adjustable lamp and boost converter frequencies, simply by applying external resistors. A new H-Bridge design reduces audible noise by creating smoother AC voltage across the EL panel. The MIC4832 is offered in MLF(R) 3mm x 3mm and MSOP8 lead-free and RoHS compliant packaging with a -40C to 85C junction temperature range. Data sheets and support documentation can be found on Micrel's web site at www.micrel.com.
Features
* * * * * * * * * * 1.8V to 5.5V DC input voltage 220Vpp output voltage capable Low audible noise EL drive waveform Supports EL panel sizes up to 3in2 (19cm2) Low 45A operating supply current Small inductor size with low profile (220uH) Tiny 8-pin 3mm x 3mm MLF(R) package Adjustable boost converter frequency Adjustable EL lamp frequency 10nA shutdown current
Applications
* * * * * * * * LCD panel backlight Mobile Phones PDAs Pagers Calculators Multimedia Players Remote controls GPS Receivers
___________________________________________________________________________________________________________
Typical Application
Low Noise EL Driver
MLF and MicroLeadFrame is a registered trademark of Amkor Technologies, Inc. Micrel Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel +1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
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Ordering Information
Part Number MIC4832YML MIC4832YMM
Note *MLF(R) is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Junction Temp. Range -40 to +85C -40 to +85C
Package 8-Pin 3mm x 3mm MLF 8-Pin MSOP
(R)
Lead Finish RoHS Compliant / Pb-Free / Halogen Free* RoHS Compliant / Pb-Free
Pin Configuration
8-Pin MSOP (MM)
8-Pin 3mm x 3mm MLF(R) (ML)
Pin Description
Pin Number 1 2 Pin Name VDD RSW Pin Function 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 GND disables the switch oscillator and shuts down 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 5 6 7 8 GND SW CS VB VA Ground 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. EL Output: Connect to one end of the EL lamp. Polarity is not important.
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Absolute Maximum Ratings(1)
Supply Voltage (VDD)...................................... -0.5V to 6.0V Output Voltage (VCS) ..................................... -0.5V to 120V EL Lamp Terminals (VA, VB)................................... VCS + 3V Switch Voltage (Vsw) ..................................... -0.5V to 120V Frequency Control Voltage (VRSW, VREL) ................................... -0.5V to (VDD +0.3V) Storage Temperature (TS).........................-65C to +150C ESD Rating(4) ............................................................... 1.5kV
Operating Ratings(2)
Supply Voltage (VDD).................................... +1.8V to +5.5V Lamp Drive Frequency (fEL) ....................... 60Hz to 1000Hz Switching Frequency (fSW).........................65kHz to 250kHz Ambient Temperature (TA) .......................... -40C to +85C Package Thermal Resistance(3) MSOP (JA) .....................................................206C/W MLF-8L (JA)......................................................63C/W
Electrical Characteristics(5)
VIN = VDD = 3.0V, RSW = 338K, REL = 1.78M. TA = 25C unless otherwise specified. Bold values indicate -40C TA +85C Parameter On-resistance CS Voltage Variation Enable Input Low Voltage (turn-off) Enable Input High Voltage (turn-on) Shutdown current Input supply current VDD = 1.8V to 5.5V VDD = 1.8V to 5.5V RSW Resistor = LOW; REL Resistor = LOW; VDD = 5.5V RSW Resistor = HIGH; REL Resistor = HIGH; VCS = 110V; VA, VB OPEN Input current including inductor VA - VB output drive frequency Switching transistor frequency Switching transistor duty cycle
Notes: 1. 2. 3. 4. 5. Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = (TJ(max) - TA) / JA. Exceeding the maximum allowable power dissipation will result in excessive die temperature. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. Specification for packaged product only.
Condition ISW = 100mA
Min 91
Typ 3.8 105
Max 7 119 0.5
Units Ohm V V
VDD0.5 0.01 45 0.5 75
A A
VIN = VDD = 3.2V; RSW = 338K, REL = 1.78M; L=220H; ROUT =10k; Lamp = 2in2 REL = 1.78M RSW = 338K 158 90
24 200 112 90 242 134
mA Hz kHz %
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Typical Characteristics
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Functional Diagram
Figure 1. MIC4832 Block Diagram
Functional Description
Overview The MIC4832 is a high-voltage EL driver with an AC output voltage of 220V peak-to-peak capable of driving EL lamps up to 3 in2. Input supply current for the MIC4832 is typically 45A reducing to 10nA in shutdown. 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 EL lamp. 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 flows into the switch. The switching MOSFET will typically turn on for 90% of the switching period. 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. When the EL oscillator is enabled, VA and VB switch in opposite states to achieve a 220V peak-to-peak AC output signal. The external resistor that connects to the REL pin determines the EL frequency.
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VA (50V/div)
IIN = 17mA L = 220H COUT = 2.7nF LAMP = 2 in2 RSW = 300k
VA (50V/div)
VIN = 3.6V
VIN = 3.6V IIN = 27mA L = 220H COUT = 2.7nF LAMP = 2 in2 RSW = 332k
VB (50V/div)
VA - VB (100V/div)
Time (2ms/div)
VA - VB (100V/div)
VB (50V/div)
REL = 2.82M
REL = 1.78M
Time (2ms/div)
Figure 2. 100Hz Output Waveform
Figure 3. 200Hz Output Waveform
f SW (kHz) =
36 R SW (M )
VA - VB (100V/div)
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 the "Typical Characteristics: Switching Frequency vs. SW Resistor" or use the equation below. The switching frequency range is 65kHz to 250kHz, with an accuracy of 20%. In general, the lower the switching frequency, the greater the input current is drawn to deliver more power to the output. However, the switching frequency should not be so low as to allow the voltage at the switch node or the CS pin to go beyond the absolute maximum voltage of those pins.
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)
VIN = 3.6V IIN = 21mA L = 220H COUT = 2.7nF LAMP = 1 in2 RSW = 353k
VB (50V/div)
REL = 1.1M
Time (2ms/div)
EL Frequency The EL lamp frequency is controlled via an external resistor connected between REL pin and VDD pin of the device. The lamp frequency increases as the resistor value decreases. For resistor value selections, see the "Typical Characteristics: EL Frequency vs. EL Resistor" graph on page 4 or use the equation below. The EL lamp frequency range is 60Hz to 1000Hz, with an accuracy of 20%.
fEL (Hz ) = 360 R EL (M )
Figure 4. 300Hz Output Waveform
Enable Function The MIC4832 is disabled by connecting the external resistor (Rsw) to GND. This turns off the switch oscillator of the boost converter. Connecting the external resistor (Rsw) to VDD enables the oscillator and turns on the device. The enable voltage should rise or fall monotonically without interruption.
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Application Information
Inductor A 220H Murata (LQH4C221K04) inductor is recommended for most applications. Generally, inductors with smaller values can handle more current. Lowering the inductance allows the boost regulator to draw more input current to deliver more energy every cycle. As a result, a lower value inductor may be used to drive larger panels or make the current panel brighter. However, caution is required as using a low value inductor with a low switching frequency may result in voltages exceeding the absolute maximum rating of the switch node and/or the CS pin. If the application uses a low input voltage (1.8 to 3V), a lower value inductor, such as 100H, may be used in order to drive the EL lamp at max brightness without issue. Diode An ideal diode to use would be 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 BAV20WS or BAS20W. Output Capacitor Low ESR capacitors should be used at the regulated boost output (CS pin) of the MIC4832 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 MIC4832 circuit. Selection of the capacitor value will depend upon the peak inductor current, inductor size, and the load. The MIC4832 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 capacitances up to 2.7nF at 200V to 250V rating in 0805 size. If output ripple is a concern a 0.01F/200V X7R output capacitor is recommended.
EL Lamp Terminals (VA, VB) An EL lamp is connected from VA to VB as the load. The high voltage alternated across VA and VB by the H-Bridge cycles generate luminance. The voltage at VA and VB should not exceed the voltage at VCS by more than 3V. This situation may become present when noisy enable signals such as those often generated by mechanical switches are applied to the driver's inputs. To prevent over voltage at VA and VB, 10k resistors may be placed in series from VA to the EL panel and from VB to the EL panel. An alternative to the use of 10k resistors is to apply a diode from the CS pin to VA and VB, where the cathode of the diode is on the CS side and the anode is on the VA and VB side, respectively.
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Application Circuit
Figure 5: Typical Li-Ion Powered MIC4832 Circuit
Size (inch2) 0.4 1 2 3
Capacitance (nF) 2 5 10 15
Lamp Frequency (Hz) REL (M) RSW (k) fSW (kHz) RSW (k) fSW (kHz) RSW (k) fSW (kHz) RSW (k) fSW (kHz)
100
2.82 240 150 257 140 300 120 313 115
200
1.69 252 143 295 122 333 108
300
1.1 273 132 353 102
400
0.837 281 128
500
0.665 257 116
600
0.562 269 105
700
0.471 281 98
800
0.409
900
0.369
Note: Table 1 applies to circuit shown in Figure 5.
Table 1: Recommended RSW & REL values for various panel sizes
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Layout Recommendation
Top
Bottom
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Package Information
8-Pin MSOP (MM)
8-Pin 3mm x 3mm MLF (ML)
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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. (c) 2007 Micrel, Incorporated.
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