iPad Oscilloscope Measuring Settling Time

This picture depicts the settling time of a waveform’s response to a step function stimulus at the input. Conventional settling time is defined as the elapsed time from the application of a step at the input to the time at which the device output enters and remains within a specified error band around the final (steady state) value. Oscilloscopes like Oscium’s iMSO-104 handheld device are typically used for these time-based voltage measurements.

Settling Time: Critical Voltage Transient Measurements

Settling time is just one of several voltage transient measurements used to describe a waveform’s timing characteristics. In fact, settling time measurements are frequently used to characterize waveforms in power, digital, analog and even RF applications. Here are a few general case examples for the different applications. For specifying power supplies the settling time describes the necessary time for the supply voltage to reach its steady state value after a power-off to power-on transition. RF engineers will use the settling time measurement to quantify a receiver’s “recovery time” – how quickly does the receiver return to linear operation after the application of a high power input signal. Lastly, the signal integrity for a high speed digital bus is greatly affected by the settling time of the Clock and Data waveforms because sampling errors are more frequent as the bit rate exceeds the system accuracy set by the settling time.

Texas Instruments Article Explains Fast Op Amp Settling Times

Attached to this blog post is an article from Texas Instrument, recently published in the company’s Analog Applications Journal, discussing a Sample and Hold (S/H) technique for measuring the settling time for a high speed operational amplifier. The high speed data rates used in modern digital and wireless communication requires hardware capable of achieving shorter and shorter settling times. Corporate officers, marketing executives and systems engineers have the luxury to take the big picture perspective by dictating the top level requirements needed to satisfy customer demands for wider bandwidth and faster data transfers without concerning themselves too much with the sometimes excruciatingly painful details of making the “thing” actually work as expected. Design engineers rely on component manufacturer datasheets, powerful computer driven software simulation applications, and minimal prototype testing to create the circuits that will someday realize the performance requirements. Ultimately, however, the burden of proving the hardware is capable of achieving the necessary timing requirements falls on the test engineers, and measuring nanosecond settling times is no easy feat. Fortunately component manufactures frequently provide App Notes and White Papers that discuss the challenges of measuring high speed data and offer test circuit examples supplemented with case studies and application circuits.

After reading the article and considering its applications, Oscium would love to hear from you about your projects that had tight timing measuring requirements and how the measurement challenge was solved. Please leave your comments/insights below...

PDF icon Power Supply Noise Performance - TI Article.pdf