AD5644 Full Scale Question

Question

Hi, 
 It's not exactly clear from the datasheet if for the external reference case the buffer amplifier still has a gain of 2 as it has in case of using the internal reference(2.5V for AD5644RBRMZ-5 part and it has a range from 0-5V). 
 My system reference is 2.5V too,so will I see close to 5V or close to 2.5V for the maximum scale code? 
 Also it's a good idea to place a 1nF decoupling capacitor on the refrence line close to the DAC? 
 The system reference is buffered at unity gain by an LTC2057 opamp. 
 Thank you, 
 Andrei

iandal · Accepted Answer

Hi Andrei, 
 Apologies if it wasn't clear on the datasheet. When an external reference is used, the output range should be 0-VREF, as long as VREF < VDD. In your case, it should be 0-2.5V. 
 Placing a decoupling cap close to the input pins of the DAC would greatly help in reducing noise on the output. 
 Regards, 
 ~ian)

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AD5644 Full Scale Question

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