The stability and cleanliness, from a noise perspective, of power sources are vital for the reliable operation of modern electronics. Power Integrity (‘PI’),  is the discipline that addresses this aspect of electronic system design and test. At Picotest we exist to ‘solve the world’s most challenging electrical testing issues’. Many of which arise from the power systems arena.

In this article, we will explore how the Picotest passive transmission line browser probes enable you to effectively design and validate your power supply performance with accurate and repeatable measurements.

First, let’s understand why ensuring Power Integrity is crucial.

  1. Meeting Recommended Voltage Requirements: High-speed digital devices are highly sensitive to voltage fluctuations and noise. Most have strict requirements for supply voltage that cannot be exceeded without impacting operational reliability. Maintaining Power Integrity is key to ensuring that the dynamic current needs of the power supply loads can be supported without violating these input requirements.
  2. Clock Jitter: In precision applications, clock jitter can occur with power fluctuations, negatively impacting the performance of components like ADCs, DACs, and other communication devices.
  3. Stability: Unstable power supplies lead to system crashes, intermittent operation, malfunctions, and reduced device lifespan due to overstress. Ensuring well-behaved responses to step load transient is a prerequisite for long-term reliability. Power distribution network (‘PDN’) impedance testing can be used to assess stability, including phase and gain margin, at the same time as target impedance and impedance flatness.
  4. Electromagnetic Compatibility (EMC): Poor power Integrity can lead to electromagnetic interference, affecting not only the device itself but also nearby equipment. Devices are required to meet EMC standards and good power integrity design plays a vital role in this.

Picotest PDN Probes and Their Role

Ensuring good power integrity in circuits with multiple power rails (i.e., virtually every electronic product nowadays) means that power supply stability and/or output impedance needs to be tested. This is especially true for any power rail below 3.3V or with high dynamic currents.

It should be noted that most power supply ICs, also known as Voltage Regulator Modules (‘VRMs’) have a worst-case end-of-life DC regulation output tolerance of about 3-4%. Most digital ICs accept a supply voltage range of +/-5%. In most circumstances, you only have about 2% variance in the supply voltage to support the voltage transients induced by load current changes, plus all the other noise sources. Essentially in round numbers that means less than 20mV of noise on a 1V supply line. To meet that, you must have both a relatively flat PDN impedance and it must meet a certain target level. In other words, if you are designing today’s electronics you need to test impedance.

At Picotest we manufacture a range of precision passive transmission line ‘Browser’ probes which greatly ease impedance  measurement. They are designed to support a wide range of measurements, making them an asset for power supply assessment.

Steve Sandler, CEO

Here’s how they contribute;

Wide Application Range: Picotest probes support impedance, step load, ripple, PSRR, noise, s-parameter, and stability testing. 

  1. Easier and Repeatable Testing: The high-bandwidth probe tip design eliminates the need for soldering SMAs or coax cables to boards. This reduces the risk of damaging delicate components and circuit cards even with repeated measurements.
  2. ‘Browser’ Style Measurement: With their small form factor and easy probe tip placement, these probes make it simple to assess multiple power rails quickly. This ability is invaluable for deciding which rails require further investigation. You can make these measurements non-invasively. For multiple rails it’s as simple as moving the probe from output capacitor to output capacitor.
  3. Stability Testing Via Non-Invasive Stability Measurement (NISM): By combining these probes with the free NISM software algorithm, you can evaluate power supply stability, at the same time impedance is tested; regardless of the power supply architecture.
  4. Compatibility: Picotest browser probes are 50 ohms and compatible with all network analyzers and oscilloscopes.

To summarize, Picotest browser probes are crafted to empower you (the engineer/designer) to attain Power Integrity, ensuring clean and stable power supplies for the dependable operation of electronic systems.

Power Integrity is no longer an optional consideration but a fundamental requirement in the design and testing of electronic systems. Clean and stable power supplies are the backbone of modern electronics, determining their reliability, performance, and compliance with EMC standards.

Picotest provides a new dimension of flexibility and precision whilst testing. Enabling engineers and designers to address Power Integrity challenges effectively, ensures that electronic devices meet the highest standards of performance and reliability. We will always continue to provide products to ensure electronic engineers are collectively designing effectively power-optimized designs.

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