MIC4830 Evaluation Board Low Noise 180Vp-p EL Driver General Description 2. Connect an EL panel. Connect the EL panel to the VA (J4) and VB (J5) terminals. The MIC4830 is a low audible noise 180Vp-p Note that polarity of the EL panel does not electroluminescent lamp (EL) driver. Using advanced matter. Bipolar, CMOS, DMOS (BCD) technology, the MIC4830 integrates a high voltage boost converter 3. Enable/Disable the MIC4830 Boost and an H-bridge driver for driving a large EL lamp. Regulator. JP1 is the enable/disable jumper The MIC4830 can drive large panel displays for for the Boost Regulator portion of the mobile phones, remote controls, MP3 players or MIC4830. Connecting JP1 to ground automotive electronics where EL panels are used for disables the boost regulator and connecting backlighting. JP1 to V enables the boost regulator. A IN The MIC4830 offers design flexibility with adjustable voltage signal may be applied to the center lamp and boost converter frequencies simply by pin of JP1 to enable or disable the boost applying external set resistors. regulator. A low voltage signal (0V) will disable the boost regulator and a high Micrels new H-Bridge design reduces audible noise voltage equal to V will enable the boost by creating smoother AC voltage across the EL panel. IN regulator. The enable voltage should rise The smooth AC voltage waveform eliminates sudden and fall between high and low monotonically changes in voltage, thus reducing the common cause without interruptions. of audible noise in EL drivers. Requirements 4. Enable/Disable the MIC4830 H-Bridge. JP2 is the enable/disable jumper for the H- The MIC4830 evaluation board requires an input Bridge portion of the MIC4830. Connecting power source that is able to deliver greater than JP2 to ground disables the H-Bridge and 200mA at 1.8V. connecting JP2 to V enables the H-Bridge. IN Disabling the H-Bridge does not disable the Precautions boost regulator. The evaluation board does not have reverse polarity protection. Applying a negative voltage to the V 5. Enable/Disable the EL panel. Both the IN terminal may damage the device. Boost Regulator and the H-Bridge of the MIC4830 must be enabled in order for the The MIC4830 evaluation board is tailored for a Li-Ion EL panel to light up. For minimum shutdown range input supply voltage. It should not exceed 5.5V current, both the Boost Regulator and the H- on the input. The MIC4830 is a high voltage, low Bridge should be turned off. The EN jumper current device and should be handled with care to (JP3) connects the V to the inductor. This IN prevent a possible electrical buzz. jumper may be used to enable or disable the EL panel on the evaluation board, without Getting Started having to use JP1 and JP2 for evaluation 1. Connect an external supply to V . Apply IN purposes. desired input voltage to the V (J1) and IN ground terminal (J2) of the evaluation board, paying careful attention to polarity and Ordering Information supply voltage (1.8V V 5.5V). An IN ammeter may be placed between the input Part Number Description supply and the V terminal to the evaluation IN MIC4830YMM EV 180Vpp MSOP Evaluation Board board. Ensure that the supply voltage is MIC4830YML EV 180Vpp MLF Evaluation Board monitored at the V terminal. The ammeter IN and/or power lead resistance can reduce the voltage supplied to the input. MLF and MicroLeadFrame are a registered trademark of Amkor Technology. Micrel, Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax 1 (408) 474-1000 Micrel, Inc MIC4830 Evaluation Board Boost Regulator Output Voltage Changing the Boost Regulator Frequency (f ) SW The boost regulator output voltage is set to 90V. The The boost regulator switching frequency may be output peak-to-peak voltage across the EL panel is changed depending upon the value of the R SW about 2 times the boost regulator output voltage resistor. The R resistor on the evaluation board is SW (180Vp-p). equal to 332k . The switching frequency may be calculated using the Rsw resistor by the following equation. EL Panel Size and Equivalent Circuit 36 Using laboratory data, it can be shown that the EL f (kHz) = SW R ()M panel has an equivalent circuit equal to a series SW resistance (Rs) with a series capacitance (C) and a Lowering the switching frequency will deliver more parallel resistance (Rp). For example, if an EL panel power to the EL panel by the boost regulator 2 is 4in , then the equivalent circuit is about 20nF of however, the switching frequency of the boost capacitance in series with 450 of resistance and regulator should not be low enough to create over- 766k of parallel resistance. Figure 1 and Table 1 shoot at the SW pin or at the CS pin. Refer to table 2 shows close approximations of the equivalent circuit for recommended values. for different EL panel sizes. Changing the EL Lamp Frequency, f EL The EL lamp frequency (H-Bridge frequency) may be changed depending upon the value of the R EL resistor. The R resistor on the evaluation board is EL equal to 1.78M. The EL lamp frequency may be calculated using the R resistor by the following EL equation. 360 f ()Hz = EL R ()M EL The higher the EL lamp frequency, the brighter the EL panel however, more brightness will require more input current, thus demand more input power. More power may be delivered to the EL lamp by increasing Figure 1. EL Panel Equivalent Circuit the input voltage or by lowering the switching frequency of the boost regulator. A table of Table 1. EL Panel Equivalent Circuit Components recommended components for typical EL panel sizes 2 and EL lamp frequency is shown in Figure 2 and Size (in) 0.40 1.0 2.0 3.0 4.0 6.0 Table 2. C (nF) 2 5 10 15 20 30 Rs ( ) 4600 1800 900 600 450 300 Rp (M ) 7.66 3.05 1.53 1.02 0.766 0.511 M9999-122007 December 2007 2 (408) 944-0800