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AD9910 output swing

Question asked by wa2pyx on Mar 25, 2011
Latest reply on Mar 28, 2011 by wa2pyx

I am confused by the output ratings.  The recommended load is 50 Ohms to ground (from data sheet pin descriptions:Open-Drain DAC Complementary Output Source. Analog output (current mode). Connect through a 50 Ω resistor to AGND.). The nominal full scale output current is 20 ma.  20 ma through 50 Ohms comes to 1V peak signal which exceeds the recommended valtage compliance range of +0.5V to -0.5V.  In my application, I use a center tapped transformer, as in the evaluation board schematic, but without the optional resistor and without the 50 Ohm resistors to ground.  Of course, if the 50 Ohm resistors were included, then the load would be 25 Ohms (on each side, 50 Ohms push-pull) and the swing would be halved.  What is the real recommendation for the 9910?  50 Ohms in each leg or 50 Ohms push pull (25 Ohms in each leg)?

Thanks,

Ray

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