Hi guys,
I'm using a DAC (the AD569JN, http://www.analog.com/static/imported-files/data_sheets/AD569.pdf) which takes a 16 bit number and outputs that as a percentage of its range. So for example I set up the DA to have a range of 0 - 5V (I have 5.2V on pin 3 and 5V on pin 2, 0V on pin 16 and -0.2V on pin 15). So if I want 5V I output 65535 (0xFFFF). That should give me exactly whatever voltage I have on the +Vref input. But instead I'm getting ~4.54V. Infact, all the voltages are scewed. If I output 13107 (0x3333) which is 1/5th of 65535, I should get 1V, but instead I get 0.91V. The forumla I'm using is this:
outputCode = 65535 * (desiredVoltage / 5);
I'm using a high precision DVM to measure these voltages, and I need the output to be as exact as possible. Is there some sort of trick to getting the correct output? I've read the datasheet several times and it seems like this should work. All the input voltages are exact, but the output just doesn't work.
BTW, I have 3 of these DACs and i've tried them all, they all give the same result.
Thanks.
I'm using a DAC (the AD569JN, http://www.analog.com/static/imported-files/data_sheets/AD569.pdf) which takes a 16 bit number and outputs that as a percentage of its range. So for example I set up the DA to have a range of 0 - 5V (I have 5.2V on pin 3 and 5V on pin 2, 0V on pin 16 and -0.2V on pin 15). So if I want 5V I output 65535 (0xFFFF). That should give me exactly whatever voltage I have on the +Vref input. But instead I'm getting ~4.54V. Infact, all the voltages are scewed. If I output 13107 (0x3333) which is 1/5th of 65535, I should get 1V, but instead I get 0.91V. The forumla I'm using is this:
outputCode = 65535 * (desiredVoltage / 5);
I'm using a high precision DVM to measure these voltages, and I need the output to be as exact as possible. Is there some sort of trick to getting the correct output? I've read the datasheet several times and it seems like this should work. All the input voltages are exact, but the output just doesn't work.
BTW, I have 3 of these DACs and i've tried them all, they all give the same result.
Thanks.