suhas_shiv
Full Member level 2
I am designing a LVCMOS driver.
It consists of a predriver and the final driver. When I am designing it for an output current of 8mA(by sizing the output driver) it works fine at around 150Mhz. But when I decrease the output driver size to operate at 2mA ( and a frequency of about 30MHz) I am not able to get the correct waveform. The problem is with the transmission line(because when I remove the tx line it works fine).
For 8mA, the transmission line charateristics are Z0=50 ohms, TD=7ns. I am using the same Tx line model for the 2mA design also. Am I supposed to increase TD because its a lower ouput current? Can the design work(atleast theoretically) with the same transmission line as in the 8mA case? What could be the problem? Thanks.
It consists of a predriver and the final driver. When I am designing it for an output current of 8mA(by sizing the output driver) it works fine at around 150Mhz. But when I decrease the output driver size to operate at 2mA ( and a frequency of about 30MHz) I am not able to get the correct waveform. The problem is with the transmission line(because when I remove the tx line it works fine).
For 8mA, the transmission line charateristics are Z0=50 ohms, TD=7ns. I am using the same Tx line model for the 2mA design also. Am I supposed to increase TD because its a lower ouput current? Can the design work(atleast theoretically) with the same transmission line as in the 8mA case? What could be the problem? Thanks.