AD5522- What mean constants 4.5 and 3.5 in transfer function?

Question

hi. I am currently building a board utilizing AD5522. However, I am completely new to DAC. I'm reviewing the datasheet, and the numbers 3.5 and 4.5 keep bugging me. What do these two numbers mean? And I would like to know how this number was created. 
 Also, what additional materials should I study to better understand this DAC? 
 thank you

mench · Accepted Answer

Hi yhpark , 
 The 3.5 and 4.5 gain setting you are seeing in transfer functions are simply the result of gain configuration of offset DAC and FIN DAC outputs. 
 The DAC amplifier gains VREF by 4.5 which gives a DAC output span of 22.5 V (as stated in the AD5522 Datasheet), the offset DAC centers that range about some chosen point. In the case of AD5522, the range is centered at 0V by default (offset DAC code =0xA492). You can read more about it in the AD5522 datasheet. 
 
 Hope this helps. You can reach out anytime if you have additional questions. 
 
 Regards, 
 Menchie)

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AD5522- What mean constants 4.5 and 3.5 in transfer function?

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