Modern Transmitters and receivers utilize compensation networks to effectively isolate receiver and ESD input capacitance from the pad of the device. A common structure is known as a T-coil, a three terminal network.
The high impedance input to a receiver is represented by the capacitively loaded center tap of the two inductors. The left side of the circuit is the die input. On the right side of the circuit is the Resistor. In order to correctly compute the frequency domain transfer function from diePad to receiver gate input, you have to drive the pad side with a 50 ohm characteristic impedance, and the center Tap with the high impedance of the receiver. Conversely, to simulate this in the time domain the termination resistance must be included as Rt in the circuit, but the waveform must be monitored by an infinite impedance probe at the Center Tap Vout.
On 5/27/2010 6:31 PM, Walter Katz wrote:
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