| Today, the LED (light emitting diode) with high brightness, low voltage, lowpower consumption, small size, long life, impact resistance and stable performancecharacteristics are rapidly gaining popularity. LED driving voltage is far less than theelectric range, while it is current-driven devices, need a stable driver circuit, anddifferent devices require different drives, LED drivers along with the LED rapiddevelopment. This article describes a12-channel12-bit LED driver circuit design, itscontent is mainly in the following innovation:1) The bandgap reference uses a more accurate second-order curvaturecompensation technique. Bandgap reference has played a crucial role in theDAC (digital to analog converter), and the temperature coefficient is animportant parameter in the bandgap reference. Traditional bandgap reference isfirst-order compensation, the second-order compensated bandgap benchmarksused in this paper has better temperature coefficient.2) Large MOS transistor current mirror output, and its structure has a lowmismatch. The mirror structure using an op-amp reduces the channel modulationeffect caused by the current mirror mismatch.3) Programmable current. Outside the DAC module, an external resistor,according to the needs of the actual current size, select different resistor.This paper, a detailed description of the design of a12Way,12-bit LED drivercircuit. The chip provides a constant current of2mA to45mA range, and the currentcan be adjusted via an external resistor. The chip can be used for LED light bar, LEDcurtain light, LED building decorative lighting.In this paper, the main analog anddigital blocks is presented separately. Highlights the DAC internal operationalamplifiers, bandgap reference, and several other modules as well as the overallfunction implementation.Finally, using the Cadence specter simulation software, amodule circuit chip and the global circuit simulation. Meanwhile, the input voltageneeds to control0V~5.5V, Operating temperature range is-10°~to+85°，forthe serial data sent by the external circuit control, the internal clock frequency is very low,200KHZ following. |
