Power Electronics
Test Probes Measure Ultra-Low Impedances

Test Probes Measure Ultra-Low Impedances

Picotest released two 50 W transmission line test probes. Coined 'PDN' Probes, for their effective use in measuring the ultra-low impedances found in power distribution networks, these precision 1x probes support a variety of measurements including impedance (1 Port Reflection, 2 Port Series and Shunt thru, non-invasive stability, PCB resonances), transient (step-load, ripple, TDT/TDR, clock jitter), and spectrum (noise, etc.). By controlling the impedance very precisely, thereby eliminating nearly all parasitic capacitances and inductances, and incorporating an infinitely variable lead pitch design, these compact probes have much higher bandwidth than most 1X probes, lower noise than active probes, and greatly improved SNR.

The 1-port probe, being a unity gain wide bandwidth probe, allows the measurement of ripple and noise with optimum signal to noise ratio (SNR).  The 2-port probe can be used to transmit a load current step through one port, while measuring the response from the other port, simultaneously.  The probes can both be used to inject noise for the assessment of sensitivity to the power supply for sensitive circuits such as clocks and LNAs. The probes are supported by a wide range of signal injectors and accessories, such as DC blockers, preamplifiers, and high speed current injectors.

The high-bandwidth (DC-1.3GHz), variable-pitch probe design enables accurate impedance measurements for high-speed PCB development and manufacturing. It eliminates the need for soldering SMA cables to your board and the risk of damaging fine copper pads or pulling up small components. You can get connectivity to circuit boards and devices without connectors. The probes come with interchangeable tips providing the user a choice of input connections, resistances, and sensitivities.

High speed applications put pressure on the measurement of power supply busses to unprecedented frequencies. As an example, the measurement of power distribution network (PDN) impedance for FPGAs generally requires the measurement of impedance levels in the milliohm scale at frequencies exceeding 1GHz. Measuring the high speed step load response in power systems using 2-port impedance is difficult because of the need to connect two 50? transmission lines to the output capacitor.  Compounding this difficult task is that these measurements often need to be made in very small circuits such as cell phones, solid state disk drives, and computer tablets; to name just a few examples.

These  1 Port and 2 Port PDN probes alleviate many of these challenges while maintaining the precision 50 W characteristics required for the measurements.

The probes are designed to work with the Picotest J2180A low noise preamplifier to improve signal to noise performance and the J2102A common mode transformer which eliminates the DC ground loop. Transmission line probes are a special type of passive probe that replaces the high impedance probe cable found in a traditional passive probe with a precision transmission line, that has a characteristic impedance that matches the oscilloscope's input (50W). This greatly reduces the input capacitance to a fraction of a picofarad, minimizing the loading of high frequency signals.

The probes are useful in applications that produce fast rising, narrow pulses with amplitudes which exceed the dynamic range of active probes. They also tend to have less parasitic effects on frequency response and so they are ideal for measuring impedance.

The probes are available today. The 1 Port PDN probe is priced at $1,495. The 2 Port PDN probe is priced at $2,495. The PDN Probe Bundle, including both probes is $3,495. The probes are compatible with all equipment including VNAs, oscilloscopes, and spectrum analyzers and come with an accessory kit that includes various probe tips and lead extenders, as well as, a DC blocking device.

 

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