| ??? 05/18/07 20:36 Read: times |
#139499 - need for isolating signals |
To achieve a good resolution and accuracy we thought it would be better to separate the digital ground of microcontroller with that of the DAC since the fast switching characteristics of the digital section can induce noise in the DAC. Now for this purpose we plan to isolate the control signals of the DAC namely , cs/ld, sck, sdi ,sro,ldac from the digital gnd of microcontroller and hence we are using 6n137 optoisolator . But this isolator inverts the logic at it's output so, we need to use a hex inverter 74hc14 so that the dac see's the right logic at it's input. Based on this background i have the following questions. 1> What is the need to place inverter IC 74HC14 between DAC and my isolator I could simply reverse my logic of code i.e. active low signals to active high and vice versa at the microcontroller before sending it through isolator and send the commands to the DAC should'nt it serve fine? 2> If at all I have to use a inverter should it be between isolator and DAC or between microcontroller and isolator? 3> If we make our entire analog circuit on one board and digital on another i.e the DAC and ADC on a single board connected to the microcontroller board via a FRC connector then will still there be a need of isolating the control and data signals from and to the microcontroller ? microcontroller p89c51 DAC - LTC2704 ADC - mcp3551 kindly reply asap.. |
