The LM3492/-Q1 integrates a boost converter and a two-channel current regulator to
implement a high efficient and cost effective LED driver for driving 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, and a nearly constant switching frequency programmable from 200 kHz to 1
MHz. The application circuit is stable with ceramic capacitors and produces no audible noise on
dimming. The programmable peak current limit and soft-start features reduce current surges at
start-up, and an integrated 190 mΩ, 3.9-A N-Channel MOSFET switch minimizes the solution
The fast slew rate current regulator allows high frequency and narrow pulse width dimming
signals to achieve a very high contrast ratio of 1000:1 at a dimming frequency of more than 3 kHz.
The LED current is programmable from 50 mA to 200 mA by a single resistor.
To maximize the efficiency, Dynamic Headroom Control (DHC) automatically adjusts the
output voltage to a minimum. DHC also facilitates a single BOM for different number of LED in a
string, which is required for backlight panels of different size, thereby reducing overall
development time and cost. The LM3492/-Q1 comes with a versatile COMM pin which serves as a
bidirectional I/O pin interfacing with an external MCU for the following functions: power-good,
overtemperature, IOUT overvoltage and undervoltage indications, switching frequency tuning, and
channel 1 disabling. Other supervisory functions of the LM3492/-Q1 include precise enable, VCC
undervoltage lockout, current regulator over-power protection, and thermal shutdown protection. The
LM3492/-Q1 is available in the thermally enhanced 20-pin HTSSOP package.
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