Picotest Transient Load Steppers

In a major technological leap, Picotest, maker of custom test equipment for power integrity and power systems testing, has released a series of very high-speed transient load current steppers for power integrity, thermal design power (TDP), IC package evaluation, and power systems testing that transforms the state-of-the-art in the industry. This is a welcomed and essential development for demanding low-voltage, high-current applications including data centers, AI, graphics, EV, and servers. 

The capabilities are being demonstrated for the first time at the SC23 Super-Computing conference in Denver, CO (Nov 12-15, 2023). 

Voltage Regulation Module (‘VRM’) and power distribution network (‘PDN’) validation, including start-up and dynamic transient performance, stability, and noise require very fast load current transitions, high peak and average power, and suitable form factors for the test equipment interface. 

Picotest’s new line of load steppers utilize custom GaN technology and innovative power delivery formats and cooling to meet the requirements of these demanding power systems. Power levels up to 2000 Amps, 2000W average power (125W-125A/in2), up to 100% duty cycle, load current step rates that are sub-ns (<500ps), with DC – 50Mhz repetition rates. These edge rates and average power levels exceed current capabilities by orders of magnitude. 

“Many novel technologies needed to come together to develop this product line and to enable them to be customizable. “Custom solutions are what Picotest has become known for,” states Steve Sandler, Picotest CEO. “Extensive use of GaN, custom-designed resistors, and innovative cooling mechanisms all needed refinement. The need for this test capability led us down a path, and we ultimately succeeded.” 

High-Speed Transient Load Steppers

The product line includes three levels based on load current and delivery form factor: less than 10A, 10A-50A, and up to 2000A. Both open and closed-loop control options are offered. The under 10A solution comes in a hand-held browser style probe format that fits into tight places. The open-loop current step is a single pre-defined current step. The 10A-50A solution is a water-cooled browser-style probe format with 6 user pre-defined current steps (6-bit logic level control). The 2000A solution is provided in a custom format as an in-socket, ASIC replacement PC card connecting to the customer’s motherboard through a custom elastomer connector/interface. The step loader replaces the ASIC that normally loads the power rails, allowing thorough power rail validation. This solution allows programmed and custom load current profiles from 0 to 2047A in 1 Amp steps using an 11-bit controller and custom design GaN/resistor networks. This level includes very high-power density, supporting full power at DC for TDP and load line testing. 

“We haven’t seen this level of GaN integration used in any product. It’s amazing what Picotest has accomplished,” states Alex Lidow, EPC CEO. 


All products are available for delivery and customization. Pricing upon request. 

Problems Addressed and Technological Breakthroughs Solved 

Good power integrity design is critical to system performance and product reliability. Verifying and validating power distribution networks (PDNs) requires both impedance and transient performance testing. The power distribution networks that provide power to expensive and unique digital loads such as CPUs, ASICs, FPGAs, and other custom ICs need to be validated before the actual ICs are tested.

“You don’t want to plug in a million-dollar ASIC to find out a dynamic load transient destroyed the part,” states Sandler.  

These load steppers solve several pressing hurdles for power integrity testing. Electronic loads are too slow and present too much capacitance to allow a valid measurement to take place. Their edge rates are too slow to address the bandwidths needed to test PDN performance. They are unable to achieve the average and peak power levels needed. Additionally, the overly inductive interconnections between industry-standard load step generators also make them too slow. 

GaN Cell close up with rice grain

GaN Cell with Rice Grain for size

The high bandwidth and elevated power/current of the power supplies in ‘Big Data’ applications require a fresh approach. 

To achieve these performance breakthroughs, Picotest pushed the limits of GaN density, developed custom resistors, developed advanced cooling techniques, and integrated high-speed digital control. Various form factors including novel probe heads were developed to allow load step testing on a rail-by-rail basis. Key to getting the edge rates necessary to test the high bandwidths associated with low voltage PDNs was the reduction to near-zero inductance of the interconnect between the steppers and the PCB where the load step is applied. Given the minimization and very high-power densities, custom water and refrigerated cooling schemes were also implemented. Given the varied nature of the power systems architectures, care was taken to allow most of these features to be customized to application requirements. 

Transient Load Current Board and Water Cooling Manifold

About Picotest.com 

Picotest.com was founded in 2010 for the purpose of developing high performance test and measurement solutions, particularly the interface between the board being tested and the measurement instrument. Picotest specializes in high fidelity, customized test and measurement probes, injectors, and other equipment, primarily for power supply and power integrity related applications. Picotest.com aims to utilize its strong R&D capability to provide the highest quality test-related products and services to customers worldwide. Picotest.com is located in Phoenix, Arizona and serves customers worldwide. The company is led by Steve Sandler, an award-winning international expert and educator in the field of Power Integrity. 

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