[LASMO] DAC constraints

The galvanometers are controlled by an analog signal input (between -5V and +5V). So, we have to use DACs in order to convert each digital coordinate. In the ILDA Format, each coordinate are code on 16 bits, but very few microcontroller embed 16 bits DAC. It’s generally DAC of 12 bits we can find on common microcontroller (like STM32 series).
With 12 bits on each coordinate, the display resolution is 4096×4096, witch is bigger than the 4K resolution (3840×2160) ! 12 bits for each DAC are quite enough.

Most of DAC on STM32 can operate up to 1 Msps (megasamples per second) and it’s compatible with our 30Kpps (and so 30Ksps).
Most of DAC on STM32 have an output signal voltage of approximately VDD=~3,3V. If we want an -5V/+5V range, we must use an AOP. For this king of gain (<10), most of AOP can easily operate at our speed ( 30Kpps ).

In conclusion, it will be easy to find a microprocessor with DAC  requirements. The only constraint is the number of DACs: a minimum of two for the two axes but a third is required if we want use an analog LASER control (in opposite of TTL control).

Pierre Dumoulin

3 Replies to “[LASMO] DAC constraints”

  1. How will you achieve the conversion between unipolar output on the STM32 DAC (0-3.3V) and the differential input on the laser drivers (-10V – +10v)?

  2. Si on peut se passer de l’alimentation double (positive et négative), une meilleure alternative serait avec deux AOP (cf. datasheet de l’ADA4941-1YRZ)

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