2 DC / Static Drive Strength

DC / Static drive strength refers to the ability to maintain a stable output voltage level under static steady-state conditions. The DC / Status drive determines the maximum load current that the output buffer can reliably drive without significant voltage droop (not < specified V_OH levels) or distortion and is generally measured using I_OH and I_OL of the buffer.

This is the current needed by the output to source or sink while maintaining the VOH / VOL voltage levels at the specified high-level (logic 1) or low-level (logic 0). Transient drive is significant for how fast the output gets to a logic 1 (rise time) or logic 0 (fall time) while static drive maintains or keeps the output steady for a specified high-level (logic 1) or low-level (logic 0) voltage respectively.

This static current strength is crucial for making sure the stability and reliability of digital systems, especially in applications where the output buffer drives resistive loads, LED loads, and so on.

To enhance static drive strength, designers typically focus on optimizing the biasing conditions of the output transistors and minimizing output impedance across various supply voltages and process parameters.

IOH and IOL are good indicators of a device’s DC drive strength.