1. How long does it take for a power supply output voltage to change from one value to another value?
2. How long does it take for a power supply output voltage to recover to its original value following a load current change?
This customer wanted to know the answer to question 1. Luckily, both of these answers can be found in our specifications and supplemental characteristic tables.
Question 1 is referring to a supplemental characteristic that has a variety of similar names: programming speed, settling time, output response time, output response characteristic, and programming response time. This is typically described with rise time and fall time values, or settling time values, or occasionally with a time constant. Rise (and fall) time values are what you would expect: the time it takes for the output voltage to go from 10% of its final value to 90% of its final value. Settling time (labeled “Output response time” in the graph below) is the time from when the output voltage begins to change until it settles within a specified settling band around the final value, such as 1% or even 0.1%, or sometimes within an LSB (least significant bit) of the final value. My fellow blogger, Ed, posted about how this affects throughput (click here) back in September of 2013.