Python DRIVER AD5687R output voltage problem

Question

Hello, 
 
 With an FTDI module FT4232H , I send SPI command but for code under 0x4000 Voutput value is different from datasheet .I use CSn from SPI tie to sync\ 
 12 bits => 4 first LSB are unused. 
 gain 1 
 Vref interne 2.5V 
 Vlogic 3.3V 
 VDD 5V 
 Vout (code=0xFFFF) = 2,500V 
 Vout (code=0xC000) = 1,875V 
 Vout (code=0x8000) = 1,25V 
 Vout (code=0x7FF0) = 2,500V 
 Vout (code=0x4000) = 1,875V 
 Vout (code=0x2220) = 1,000V 
 Vout (code=0x0010) = 0,002V

Someone have an idea, thanks for your help.

dendalisay · Accepted Answer

Hi JBALL38 , 
 One possibility is that the GAIN pin might be misconfigured. The other possibility is that the SPI command isn&rsquo;t formatted correctly. The AD5687R requires a 24‑bit frame (4 command bits, 4 address bits, and a 12‑bit data field left-shifted by 4 bits). If the data isn&rsquo;t properly shifted or if you&rsquo;re sending only 16 bits, lower-code values can be misinterpreted. Also, if you&rsquo;re using a command that requires an LDAC pulse, make sure it&rsquo;s being applied correctly. 
 Could you share your complete system settings, schematic, or code snippet? 
 Br, 
 Den)

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Python DRIVER AD5687R output voltage problem