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| HV857 Low Noise, High Voltage EL Lamp Driver IC Features Patented audible noise reduction Patented lamp aging compensation 190 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 Available in MSOP-8 and DFN-8 packages General Description The Supertex HV857 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 95V. The chip can be enabled/disabled by connecting the resistor on RSW-Osc to VDD/GND. The HV857 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 RELOsc pin and VDD pin. An external inductor is connected between the LX and VDD pins or VIN for split supply applications. A 0.0030.1F 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 95V, 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 95V across the EL lamp. Applications LCD backlighting Mobile Cellular Phone PDAs Handheld wireless communication products Global Positioning Systems (GPS) Typical Application Circuit ON = VDD OFF = 0 Enable Signal + VDD _ CDD 1 RSW VDD VA VB CS LX 8 EL Lamp 7 6 D 5 LX CS 2 RSW-Osc 3 REL 4 GND REL-Osc VIN + _ CIN HV857MG HV857 Ordering Information Device HV857 Package Options 8-Lead DFN (K7) HV857K7-G 8-Lead MSOP (MG) HV857MG-G -G indicates package is RoHS compliant (`Green') Absolute Maximum Ratings Parameter Supply Voltage, VDD Operating Temperature Storage Temperature DFN-8 Power Dissipation MSOP-8 Power Dissipation Output voltage, VCS Value -0.5V to 6.5V -40C to +85C -65C to +150C 1.6W 300mW -0.5 to +120V Pin Configuration Top View VDD 1 RSW-Osc 2 8 VA 7 VB MSOP-8 REL-Osc 3 GND 4 6 CS 5 LX HV857MG 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. VDD RSW-Osc REL-Osc GND 1 2 3 4 8 7 VA VB CS LX DFN-8 6 5 Thermal Resistance Package DFN-8 MSOP-8 Mounted on FR4 board, 25mm x 25mm x 1.57mm ja 60OC/W 330OC/W HV857K7 Pads are at the bottom of the package Exposed center pad is at ground potential Recommended Operating Conditions Symbol VDD fEL TA Parameter Supply voltage Operating drive frequency Operating temperature Min 1.8 -40 Typ Max 5.0 1 +85 Units V kHz O Conditions ------- C 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 Electrical Characteristics DC Characteristics (Over recommended operating conditions unless otherwise specified, T =25C) A Symbol RDS(ON) VCS VA - VB IDDQ Parameter On-resistance of switching transistor Max. output regulation voltage Peak to Peak output voltage Quiescent VDD supply current Min 85 170 - Typ 95 190 - Max 6.0 105 210 150 Units V V nA Conditions I = 100mA VDD=1.8V to 5.0V VDD=1.8V to 5.0V RSW-Osc = Low 2 HV857 Electrical Characteristics (cont.) Symbol IDD IIN VCS fEL fSW D Parameter 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 205 Typ 20 84 240 80 88 Max 150 25 275 Units A mA V Hz kHz % Conditions VDD= 1.8V to 5.0V. See Figure 1 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. Block Diagram LX VDD CS RSW-Osc Switch Osc Q GND Disable C VA + _ VREF VSENSE Q High Voltage Level Translator Q VB Q VDD EL Osc REL-Osc Figure 1: Typical Application/ Test Circuit ON = VDD OFF = 0V 560k 0.1F 2.0M 4 GND 1 VDD 2 RSW-Osc 3 REL-Osc Enable Signal 2.0k VA 8 VB 7 CS 6 BAS21 LX 5 Equivalent to 3.0in2 lamp 10nF + VDD - HV857MG + VIN 4.7F 220H* 3.3nF, 100V * Murata Inductor LQH32CN221K21 3 HV857 Typical Performance Device HV857MG-G Lamp Size 3.0in2 VDD = VIN 3.3V IIN 20.0mA VCS 84V fEL 240Hz Brightness 6.0ft-lm Typical Performance Curves for Figure 1 (EL Lamp = 3.0in , V 2 DD = 3.0V) VCS vs VIN 95 VCS (V) lIN (mA) IIN vs VIN 25 23 21 19 17 15 13 1.5 85 75 65 55 1.5 2.5 3.5 VIN (V) 4.5 5.5 2.5 3.5 VIN (V) 4.5 5.5 Brightness vs VIN 7 6 5 4 3 2 1 1.5 24 22 Brightness (ft-lm) IIN vs VCS lIN (mA) 20 18 16 2.5 3.5 VIN (V) 4.5 5.5 14 55 65 75 VCS (V) 85 95 IIN, VCS, Brightness vs Inductor Value 100 90 6 80 70 VCS 5 Brightness 4 3 Iin 2 7 60 50 40 30 20 10 0 100 lIN 1 0 150 200 250 300 350 400 450 500 550 600 Inductor Value (H) 4 Brightness (ft-lm) lin (mA), VCS (V) HV857 External Component Description External Component Diode CS Capacitor Description Fast reverse recovery diode, BAS21 diode or equivalent. 0.003F to 0.1F, 100V 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. REL Resistor 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. fEL = (2M)(240Hz) REL RSW Resistor 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. fSW = (560k)(80kHz) RSW LX Inductor 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. Lamp 5 HV857 Split Supply Configuration The HV857 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 HV857. 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. Enable/Disable Configuration The HV857 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. The control signal has to track the VDD supply. 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 CDD 1 VDD 2 RSW-Osc 3 REL-Osc REL 4 GND LX 5 LX CS VA 8 VB 7 EL Lamp CS 6 D Enable Signal RSW HV857MG + VIN CIN 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. Figure 3: Typical Application Circuit for Audible Noise Reduction ON = VDD OFF = 0V RSER 1 VDD 2 RSW-Osc 3 REL-Osc REL 4 GND LX 5 LX VA 8 VB 7 EL Lamp CS 6 D Enable + VDD CDD RSW - HV857MG + VIN CIN CS - 6 HV857 Minimization of 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. 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. Effect of Series Resistor on EL Lamp Audible Noise and Brightness 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). 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. 7 HV857 8-Lead DFN Package Outline (K7) 3x3mm body, 0.80mm height (max), 0.65mm pitch D 8 D2 8 E Note 1 (Index Area D/2 x E/2) E2 1 1 Note 1 (Index Area D/2 x E/2) Top View View B Bottom View Note 3 A A3 b e Seating Plane Note 2 L L1 A1 Side View View B Notes: 1. Details of Pin 1 identifier are optional, but must be located within the indicated area. The Pin 1 identifier may be either a mold, or an embedded metal or marked feature. 2. Depending on the method of manufacturing, a maximum of 0.15mm pullback (L1) may be present. 3. The inner tip of the lead may be either rounded or square. Symbol MIN Dimension (mm) NOM MAX A 0.70 0.75 0.80 A1 0.00 0.02 0.05 A3 0.20 REF b 0.25 0.30 0.35 D 2.85 3.00 3.15 D2 1.60 2.50 E 2.85 3.00 3.15 E2 1.35 1.75 e 0.65 BSC L 0.30 0.40 0.50 L1 0.15 0O 14O JEDEC Registration MO-229, Variation WEEC-2, Issue C, Aug. 2003. Drawings not to scale 8 HV857 8-Lead MSOP Package Outline (MG) 3x3mm body, 1.10mm height (max), 0.65mm pitch D 8 1 (x4) E E1 Note 1 (Index Area D1/2 x E1/2) L L2 Gauge Plane 1 L1 Seating Plane Top View A View B View B A A2 Seating Plane A1 e b A Side View View A-A Note 1: A Pin 1 identifier must be located in the index area indicated. The Pin 1 identifier may be either a mold, or an embedded metal or marked feature. Symbol Dimension (mm) MIN NOM MAX A 0.75 1.10 A1 0.00 0.15 A2 0.75 0.85 0.95 b 0.22 0.38 D 2.80 3.00 3.20 E 4.65 4.90 5.15 E1 2.80 3.00 3.20 e 0.65 BSC L 0.40 0.60 0.80 L1 0.95 REF L2 0.25 BSC 0 8 O 1 5O 15O O JEDEC Registration MO-187, Variation AA, Issue E, Dec. 2004. Drawings not to scale. (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to http://www.supertex.com/packaging.html.) Doc.# DSFP-HV857 NR110806 9 |
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