SLAAE49 February   2022 DAC43204 , DAC53004 , DAC53204 , DAC53204W , DAC63004 , DAC63204

 

  1.   Design Objective
  2.   Design Description
  3.   Design Notes
  4.   Design Simulations
    1.     Transient Simulation Results
    2.     DC Transfer Simulation Results
  5.   Register Settings
  6.   Pseudo Code Example
  7.   Design Featured Devices
  8.   Design References

Design Description

This design uses a four-channel buffered voltage or current output smart DAC such as the DAC43204, DAC53204, or DAC63204 (DACx3204) to bias a light-emitting diode (LED). The smart DAC can configured in voltage output mode and be connected in a force-sense configuration with a bipolar junction transistor (BJT) in LED biasing applications needing a few milliamps of current as shown on channel 1 of the DACx3204 in the circuit schematic. The DAC sets the collector current of the PNP-type BJTx, such as the 2N2905, and controls the amount of current through the LED by varying the base voltage. The LED is connected between the collector of the BJT and ground. The DAC can be used in current output mode to drive the LED directly with up to 250 µA for low-current LED biasing applications as shown on channel 0 of the DACx3204 in the circuit schematic. The feedback pin (VFB) of the DACx3204 compensates for the base-emitter voltage (VBE) drop and the drift of the BJT when using the BJT configuration. The DACx3204 have a general-purpose input-output (GPIO) pin that can be used to switch the LEDs between two current values, or on and off. All register settings can be saved using the non-volatile memory (NVM) on the smart DAC, meaning that the device can be used without a processor, even after a power cycle. This circuit can be used in applications such as barcode scanners, barcode readers, currency counters, POS printers, optical modules, and appliance lighting.