The LM3492HC/-Q1 device integrates a boost converter and a two-channel current regulator to implement a highly efficient and cost effective LED driver. This device drives two individually dimmable LED strings with a maximum power of 15 W and an output voltage of up to 65 V. The boost converter employs a proprietary projected-on-time control method to give a fast transient response with no compensation required. The nearly constant switching frequency can be set to a level from 200 kHz to 1 MHz. Ceramic capacitors stabilize the application circuit and produce no audible noise on dimming. The programmable peak current limit and soft-start features reduce current surges at start-up. An integrated, 190-mΩ, 3.9-A, N-Channel MOSFET switch minimizes the solution size. The fast slew rate current regulator allows high frequency and narrow pulse width dimming signals to achieve a very high contrast ratio of 10000:1. The LED current can be set from 50 mA to 250 mA by a single resistor. For all available packages, see the orderable addendum at the end of the data sheet.
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To maximize the efficiency, (DHC) automatically adjusts the output voltage to a minimum. The DHC also facilitates a single BOM for different number of LED in a string, which is required for back-light panels of different size, thereby reducing overall development time and cost. The LM3492HC device includes a COMM pin that serves as a bidirectional I/O pin. The versatile COMM pin interface with an external micro-controller unit (MCU) is used for the following functions: power-good, overtemperature, IOUT overvoltage and undervoltage indications, switching frequency tuning, and channel 1 disabling. Other supervisory functions of the device include precise enable, VCC undervoltage lockout, current regulator over-power protection, and thermal shutdown protection. The device is available in the thermally enhanced PWP, 20-pin package.