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| Supertex inc. HV859 Initial Release High Voltage EL Lamp Driver for Low Noise Applications Features Patented audible noise reduction Patented lamp aging compensation 210 VPP output voltage for higher brightness Patented output timing for high efficiency Single cell lithium ion compatible 150nA shutdown current Wide input voltage range 1.8V to 5.0V Separately adjustable lamp and converter frequencies Output voltage regulation Split supply capability General Description The Supertex HV859 is a high voltage driver designed for driving Electroluminescent (EL) lamps of up to 5 square inches. The input supply voltage range is from 1.8V to 5.0V. The device uses a single inductor and a minimum number of passive components. The nominal regulated output voltage that is applied to the EL lamp is 105V. The chip can be enabled/disabled by connecting the resistor on RSW-OSC to VDD/ ground. The HV859 has two internal oscillators, a switching MOSFET, and a high voltage EL lamp driver. The frequency for the switching MOSFET is set by an external resistor connected between the RSW-OSC pin and the supply pin VDD. The EL lamp driver frequency is set by an external resistor connected between REL-OSC pin and the VDD pin. An external inductor is connected between the LX and VDD pins or VIN for split supply applications. A 0.003-0.1F capacitor is connected between CS and ground. The EL lamp is connected between VA and VB. The switching MOSFET charges the external inductor and discharges it into the capacitor at CS. The voltage at CS will start to increase. Once the voltage at CS reaches a nominal value of 105V, the switching MOSFET is turned OFF to conserve power. The outputs VA and VB are configured as an H bridge and are switching in opposite states to achieve 105V across the EL lamp. Applications LCD backlighting Mobile Cellular Phone keypads PDAs Handheld wireless communication products Global Positioning Systems (GPS) Typical Application Circuit ON = VDD OFF = 0V RSW CDD REL 1 2 3 Enable RSER VDD RSW-osc REL-osc GND VA VB CS LX 8 7 6 + VDD EL Lamp D - 4 5 + VIN CIN HV859MG/ HV859K7 LX CS NR040306 Supertex inc. * 1235 Bordeaux Drive, Sunnyvale, CA 94089 * Tel: (408) 222-8888 * FAX: (408) 222-4895 * www.supertex.com 1 HV859 Ordering Information Device HV859 Package Options MSOP-8 1 Thermal Resistance Package 2 ja 330 C/W 60 C/W DFN/MLP-8 MSOP-8 DFN/MLP-8 HV859MG-G HV859K7-G 1. Product supplied on 2,500 piece carrier tape reels only 2. Product supplied on 3,000 piece carrier tape reels only -G indicates package is RoHS compliant (`Green') Pin Configuration Top View* VDD 1 2 8 7 VA VB VDD 1 2 3 4 8 VA VB Absolute Maximum Ratings* VDD, Supply Voltage Operating Temperature Storage Temperature Power Dissipation MSOP-8 Power Dissipation DFN/MLP-8 VCS, Output Voltage -0.5V to 6.5V -40C to +85C -65C to +150C 300mW 1.6W -0.5V to +130V RSW-OSC REL-OSC GND MSOP-8 3 4 6 5 RSW-OSC REL-OSC GND CS LX DFN/ MLP-8 7 6 5 CS LX HV859MG *Drawings are not to scale. HV859K7 (Pads are on the bottom of the package) *Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is not implied. Continuous operation of the device at the absolute rating level may affect device reliability. All voltages are referenced to device ground. Electrical Characteristics DC Characteristics (Over recommended operating conditions unless otherwise specified VIN = VDD = 3.3V, TA=25C) Symbol RDS(ON) VCS VA - VB IDDQ IDD IIN VCS FEL Fsw D Parameter On-resistance of switching transistor Max. output regulation voltage Peak to Peak output voltage Quiescent VDD supply current Input current going into the VDD pin Input current including inductor current Output voltage on VCS EL lamp frequency Switching transistor frequency Switching transistor duty cycle Min 95 190 205 - Typ 105 210 26 90 77 88 Max 6.0 115 230 150 150 35 275 - Units V V nA A mA V Hz kHz % Conditions I = 100mA VDD = 1.8V to 5.0V VDD= 1.8V to 5.0V Rsw-osc = Low VDD = 1.8V to 5.0V. See Figure 1. See Figure 1.* See Figure 1. See Figure 1. --See Figure 1. * The inductor used is a 220H Murata inductor, max DC resistance of 8.4, part # LQH32CN221K21. Recommended Operating Conditions Symbol VDD fEL TA Parameter Supply voltage Output drive frequency Operating Temperature Min 1.8 -40 Typ - Max 5.0 1 +85 Units V kHz C Conditions ------- Enable/Disable Function Table Symbol EN-L EN-H Parameter Logic input low voltage Logic input high voltage Min 0 VDD - 0.2 Typ - Max 0.2 VDD Units V V Conditions VDD = 1.8V to 5.0V VDD = 1.8V to 5.0V NR040306 2 Functional Block Diagram VDD LX CS RSW-OSC Switch OSC C VSENSE VREF VDD RSW-OSC Switch OSC + HV859 Q High Q Voltage Level Translators Q Q VA GND Figure 1: Typical Application/Test Circuit ON = VDD OFF = 0V VDD 1 Enable Signal Equivalent to 3.0in2 lamp 2.0k 10nF 560k 2 3 2.0M 4 + VDD = VIN 1.0F - * Murata Inductor - LQH32CN221K21 ** BAS21 - General Purpose HV diode VDD RSW-osc REL-osc GND VA VB CS LX Disable VB 8 7 6 BAS21** 5 HV859MG/ HV859K7 220H* 3.3nF 200V NR040306 3 HV859 External Component Description External Component Diode CS Capacitor Selection Guide Line Fast reverse recovery diode, BAS21 diode or equivalent. 0.003F to 0.1F, 200V capacitor to GND is used to store the energy transferred from the inductor. The EL lamp frequency is controlled via an external REL resistor connected between REL-OSC and VDD of the device. The lamp frequency increases as REL decreases. As the EL lamp frequency increases, the amount of current drawn from the battery will increase and the output voltage VCS will decrease. The color of the EL lamp is dependent upon its frequency. A 2M resistor would provide lamp frequency of 205 to 275Hz. Decreasing the REL resistor by a factor of 2 will increase the lamp frequency by a factor of 2. The switching frequency of the converter is controlled via an external resistor, RSW between RSW-OSC and VDD of the device. The switching frequency increases as RSW decreases. With a given inductor, as the switching frequency increases, the amount of current drawn from the battery will decrease and the output voltage, VCS, will also decrease. The inductor LX is used to boost the low input voltage by inductive flyback. When the internal switch is on, the inductor is being charged. When the internal switch is off, the charge stored in the inductor will be transferred to the high voltage capacitor CS. The energy stored in the capacitor is connected to the internal H-bridge, and therefore to the EL lamp. 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 of the inductor (controlled by RSW) should be increased to avoid saturation. A 220H Murata (LQH32CN221) inductor with 8.4 series DC resistance is typically recommended. For inductors with the same inductance value, but with lower series DC resistance, lower RSW resistor value is needed to prevent high current draw and inductor saturation. As the EL lamp size increases, more current will be drawn from the battery to maintain high voltage across the EL lamp. The input power, (VIN x IIN), will also increase. If the input power is greater than the power dissipation of the package, an external resistor in series with one side of the lamp is recommended to help reduce the package power dissipation. REL Resistor RSW Resistor Lx Inductor Lamp Split Supply Configuration The HV859 can also be used for handheld devices operating from a battery where a regulated voltage is available. This is shown in Figure 2. The regulated voltage can be used to run the internal logic of the HV859. The amount of current necessary to run the internal logic is 150A Max at a VDD of 3.0V. Therefore, the regulated voltage could easily provide the current without being loaded down. The HV859 can be easily enabled and disabled via a logic control signal on the RSW and REL resistors as shown in Figure 2 below. The control signal can be from a microprocessor. RSW and REL are typically very high values. Therefore, only 10's of microamperes will be drawn from the logic signal when it is at a logic high (enable) state. When the microprocessor signal is high the device is enabled, and when the signal is low, it is disabled. Figure 2: Split Supply and Enable/Disable Configuration ON = VDD OFF = 0V Regulated Voltage = VDD RSW 1 2 3 Enable Signal VDD RSW-osc REL-osc GND VA VB CS LX 8 7 6 EL Lamp D REL 4 5 + VIN CIN HV859MG/ HV859K7 LX CS - NR040306 4 HV859 Figure 3: Typical Application Circuit for Audible Noise reduction ON = VDD OFF = 0V RSW CDD REL 1 2 3 Enable RSER VDD RSW-osc REL-osc GND VA VB CS LX 8 7 6 + VDD EL Lamp D - 4 5 + VIN CIN HV859MG/ HV859K7 LX CS - Audible Noise Reduction This section describes a method (patented) developed at Supertex to reduce the audible noise emitted by the EL lamps used in application sensitive to audible noise. Figure 3 shows a general circuit schematic that uses the resistor, RSER, connected in series with the EL lamp The audible noise from the EL lamp can be set at a desired level based on the series resistor value used with the lamp. It is important to note that use of this resistor will reduce the voltage across the lamp. Reduction of voltage across the lamp will also have another effect on the over all performance of the Supertex EL drivers, age compensation (patented). This addresses a very important issue, EL lamp life that most mobile phone manufacturers are concerned about. As EL lamp ages, its brightness is reduced and its capacitance is diminished. By using the RC model to reduce the audible noise emitted by the EL lamp, the voltage across the lamp will increase as its capacitance diminishes. Hence the increase in voltage will compensate for the reduction of the brightness. As a result, it will extend the EL lamp's half-life (half the original brightness). How to Minimize EL Lamp Audible Noise: The EL lamp, when lit, emits an audible noise. This is due to EL lamp construction and it creates a major problem for applications where the EL lamp can be close to the ear such as cellular phones. The noisiest waveform is a square wave and the quietest waveform has been assumed to be a sine wave. After extensive research, Supertex has developed a waveform that is quieter than a sine wave. The waveform takes the shape of approximately 2RC time constants for rising and 2RC time constants for falling, where C is the capacitance of the EL lamp, and R is the external resistor, RSER, connected in series with the EL lamp. This waveform has been proven to generate less noise than a sine wave. Effect of Series Resistor on EL Lamp Audible Noise and Brightness: Increasing the value of the series resistor with the lamp will reduce the EL lamp audible noise as well as its brightness. This is due to the fact that the output voltage across the lamp will be reduced and the output waveform will have rounder edges. NR040306 5 HV859 8-Lead MSOP Package Outline (MG) 0.116 0.004 (2.946 0.102) D Note: Circle (e.g. B ) indicates JEDEC Reference. Measurement Legend = Dimensions in Inches (Dimensions in Millimeters) Full Circle, or Half Circle, B 0.013 0.005 (0.330 0.127) H 0.193 0.006 (4.902 0.152) E 0.118 0.004 (3.000 0.102) 12 4 0.040 0.003 A (1.016 0.076) 3.0 3 A1 e C L 0.004 0.002 (0.102 0.051) 0.0256 BSC (0.650) 0.006 0.0003 (0.152 0.0076) 0.0215 0.006 (0.546 0.152) 8-Lead DFN/MLP Package Outline (K7) 3.00 1.500 3.00 1.55 2.40 1.40 1.80 1.500 0.20 0.40 Pin #1 Index Top View 0.65 0.23 0.37 Bottom View 0.70 0.80 0.20 Side View All dimensions are in millimeters Legend: min max Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell its products for use in such applications, unless it receives an adequate "product liability indemnification insurance agreement". Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the Supertex website: http//www.supertex.com. (c)2006 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited. Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: (408) 222-8888 / FAX: (408) 222-4895 Doc.# DSFP - HV859 NR040306 www.supertex.com 6 |
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