Part 2: Dielectric Loss Consider a circuit trace carrying a 3 Gbps SATA signal.
ID: 3349111 • Letter: P
Question
Part 2: Dielectric Loss Consider a circuit trace carrying a 3 Gbps SATA signal. It has a 250 mV logic swing. The trace is routed over a circuit board material that has a dielectric loss adder of 4 ps/cm. If the trace is routed 40 cm on the board, what is effective rise time of the dielectric loss? If the SATA signal has a rise time at the driver of 100 ps, what is the rise time of the signal at the other end of the trace? How long can the signal be routed and keep the overall rise time (combination of driver rise time and rise time due to dielectric loss) below 175 ps? 5. 6. 7.Explanation / Answer
5. The dielectric loss per cm = 4 ps/cm
The length of route = 40 cm
Effective loss = 40 x 4 = 160 ps
6. In rise time at driver = 100 ps. At other end rise time will be some of input rise time and effective loss.
The rise time at other end = 100 + 160 = 270 ps
7. Max route length = Max Rise time/ Rise Time per length = 175 ps / 4 ps per cm
Max route length = 43.75 cm