Hi all,
I have a question regarding matching the impedance of a digital to analog converter to the entry stage of an RF board. The DAC we are using is the DAC5687 from TI. (**broken link removed**)
The output of the DAC is differential and in our board we have the track on the PCB set for an impedance of 50 ohms (22 for each differential pin). We measure a signal with 0.6V pk-pk on the output (0.3 on each differential pin) giving a current of 6mA when measured across a 50ohm load (please correct me if this in incorrect). Now the problem is that initially the RF board is expecting a signal with a limit of +/- 10mA. The problem is that their board is set with an impedance of 25 ohms in total. (12 ohms in each differntial pin). My question is, how does the output current of the DAC change when connected to this load?
If the tracks on the DAC board were also changed by the same amount i.e. to give an impedance also of 25 ohms then I assume the current would double to 12mA. Please confrim if my thinking is correct here.
But what happens when the impedance on the DAC board is 50 ohms in total and on the RF board its 25 ohms in total. How would this affect the output current?
Many thanks for any advice.
I have a question regarding matching the impedance of a digital to analog converter to the entry stage of an RF board. The DAC we are using is the DAC5687 from TI. (**broken link removed**)
The output of the DAC is differential and in our board we have the track on the PCB set for an impedance of 50 ohms (22 for each differential pin). We measure a signal with 0.6V pk-pk on the output (0.3 on each differential pin) giving a current of 6mA when measured across a 50ohm load (please correct me if this in incorrect). Now the problem is that initially the RF board is expecting a signal with a limit of +/- 10mA. The problem is that their board is set with an impedance of 25 ohms in total. (12 ohms in each differntial pin). My question is, how does the output current of the DAC change when connected to this load?
If the tracks on the DAC board were also changed by the same amount i.e. to give an impedance also of 25 ohms then I assume the current would double to 12mA. Please confrim if my thinking is correct here.
But what happens when the impedance on the DAC board is 50 ohms in total and on the RF board its 25 ohms in total. How would this affect the output current?
Many thanks for any advice.