The power delivery network distributes and delivers the DC power to all active components on the board. Disturbances on power rails can cause serious impairments in the performance of the used ICs and the overall system, so power integrity is a paramount goal in board design.
As rail voltages get smaller and tolerances get tighter, measurement noise makes it difficult to get accurate ripple and noise values. It can therefore be problematic to quickly determine if there are disturbances on the power rail. For instance, using a standard 500 MHz passive probe with a 10:1 attenuation results in additional measurement noise, causing overstated peak-to-peak voltage measurements and masking signal details as shown in the screenshot below.
There is a wide range of solutions to ensure proper power-up and power-down sequencing in your design. To address potential challenges, Rohde & Schwarz has developed a probe for accurate and quick power rail measurements. The R&S
RT-ZPR20 active power rail probe has a 1:1 attenuation ratio, very little noise and enough bandwidth to not attenuate critical signal content. The captured waveform includes higher frequency transients riding on the rail.
The R&SRTM3000 or the R&SRTA4000 oscilloscope are both powerful tools that help to efficiently and precisely analyze unwanted disturbances on your power rails and to identify their root cause. A combination of these low-noise oscilloscopes with the R&SRT-ZPR20 power rail probe allows for more accurate power rail measurements.
The most important benefits using such a combination can be summarized as follows:
- The probe’s 1:1 attenuation provides minimal noise for a system noise of less than 500 μV (at 1 GHz bandwidth and 10 mV/div)
- With ±60 V of built-in offset, users can center and zoom in a wide variety of DC rail voltage standards without worrying about how much built-in offset the scope has. The offset eliminates the need to use AC coupling or DC blocking capacitors, which impede the ability to see true DC values and drift
- High-frequency transients and coupled signals are isolated. The probe’s rated bandwidth is 2 GHz. When used with an R&SRTA4000 or R&SRTM3000, overall bandwidth is set by the oscilloscope bandwidth
- 50 kΩ DC input impedance minimizes loading, so DC values remain accurate
- An integrated 16-bit R&SProbeMeter provides a simultaneous five-digit readout of each power rail’s DC value
More detailled information about R&S power rail probes can be found here!