Status: In Production
HV816 is a high voltage Electroluminescent (EL) lamp driver designed for driving a lamp capacitance of up to 150nF, or an area of approximately 42 square inches. It is comprised of a boost converter followed by an H-bridge. The boost converter produces a regulated output voltage, which is set at a nominal value of 180V using an internal reference voltage. The H-bridge is used to produce a differential output drive and the EL lamp will therefore see ±180V (360V peak-to-peak). The HV816 has two internal oscillators, one for controlling the boost converter switching frequency and the other for controlling the H-bridge switching frequency. Having separate control of each switching frequency allows flexibility in the circuit design. The operating input supply voltage is 2.7 to 5.5V, but the Enable (EN) and Select (SEL) interface to the device will accept logic high levels down to 1.5V. The EN input is for turning the device ON and OFF. The SEL input is for external logic control of the H-bridge switching frequency, if required. The HV816 boost converter stage uses a single inductor and a minimum number of external components. The input voltage to the inductor can be different from the input voltage to the HV816 (split supply). The external inductor is connected either between the LX and VDD pins or, for split supply applications, between the LX pin and a higher voltage supply (shown as VIN in the Block Diagram). An external MOSFET has to be driven by the switch oscillator to generate a high voltage. The switching frequency for this MOSFET is set by an external resistor connected between the RSW-Osc pin and the supply pin VDD. During operation, the external switching MOSFET turns on and allows energy to be stored in the inductor; this energy is transferred into the capacitor CS when the MOSFET turns off. The voltage at the CS pin will increase with every switching cycle. Once the voltage at the CS pin reaches the desired regulation limit, nominally 180V, the external switching MOSFET is turned OFF to conserve power. The CS capacitor is connected between the CS pin and ground; the CS pin is internally connected to the H-bridge. Energy from the boost converter stage is stored in the capacitor before being transferred to the EL lamp. Depending on the EL lamp sizes, a 1.0nF to 15nF capacitor should be used for CS. The EL lamp switching frequency can be in the range of 100Hz to 1.0kHz. This frequency can be set by either an external logic signal at the SEL pin, with a frequency that is 4 times the desired EL lamp switching frequency, or by an external resistor connected between the REL-Osc and VDD pins. If external frequency is input to the device at the SEL pin, the REL-Osc pin should be connected to ground. The HV816 has the provision to control the discharge rate of the output to minimize audible noise emitted by the EL lamp, which is connected between the VA and VB pins. An external resistor from the RSLEW-OUT pin to ground controls the VA, VB output discharge rate. EL lamp dimming can be accomplished by changing the input voltage to the VREG pin. The VREG pin allows an external voltage source to control the VCS amplitude. The VCS voltage is approximately 143 times the voltage at the VREG pin.
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