Apparatus for Improving the Accuracy of an Exponential Current Digital-to-Analog (IDAC) Using a Binary-Weighted MSB

摘要

An apparatus of an exponential current digital-to-analog converter (IDAC) using a binary-weighted MSB to efficiently drive current controlled light emitting diode (LED) devices. The apparatus comprises of an exponential current digital-to-analog converter (IDAC) current source, a voltage buffer to create an active cascode at the output stage, and an error amplifier that by means of a DC-DC converter voltage loop imposes an appropriate voltage at the output of the IDAC, depending on the current load set to drive the LEDs. The definition of the apparatus involves defining an exponential LSB and exponential MSB current mirrors according to a defined methodology.

主权项

1. An apparatus for driving light emitting diode (LED) elements comprising:
an error amplifier; a pulse width modulation comparator electrically connected the output of said error amplifier; a DC-DC converter electrically connected to the output of said pulse width modulation comparator and an output pad; at least one light emitting diode (LED) electrically connected to the input of said error amplifier; and an exponential current digital-to-analog converter (IDAC) using least significant bit (LSB) and a binary weighted most significant bit (MSB) wherein said binary weighted most significant bit (MSB) is electrically connected to said cathode of said light emitting diode (LED) and input of said error amplifier wherein said binary weighted MSB is defined according to a specified relationship for IMSB providing an MSB code for the MSB network initiating the MSB switches.