Thevenin Modeling Use Cases

In general, low-order impedances are ubiquitous in analog audio designs.  In modeling designs, pin compatible models are developed for some level of block design.  The interconnect of the analog blocks is often produced from the schematics.  While the blocks are independent, their electrical interactions are not.  Here are some of the few example use cases I have encountered.

DISCRETE DEVICES
	Many discrete devices are used in chip- and system-level design.  Examples include reference resistors, charge-pump capacitors, boost converter inductors, AC coupling capacitors, and so on. 

I/O IMPEDANCES
	Anytime voltage sources have high impedance, or current sources have low impedance, they are subject to inefficient power transfer or corruption via improper loading.  For example, reference voltages that are passed through RC filters may be sensitive to receiver loading.  Also, matching the driving and load impedances is critical in some power and telephony applications.  A recent design I encountered used the speaker load inductance as part of a filter for a class-D amplifier.

MULTIPLEXED OR DISABLED DEVICES
	Various devices may power down into a high impedance state, either to multiplex on a transmission line or to enter a low power state.
