Integrity Checks on DC Supply Voltages
The integrity and stability of DC supply voltages in printed circuit board designs are increasingly becoming a decisive factor in the reliability of electronic products. Advances in semiconductor technology have meant that the supply voltage levels required for components have continuously fallen. Voltage levels of 5 V were typical a number of years ago, while components today often have to be driven with 3.3, 1.8, 1.5 or even 1.1 V. With every reduction in supply voltage levels, the tolerance range likewise shrinks. This has the effect that disturbances, such as noise, ripple effects, transient currents or overshoots transgress tolerance limits and lead to malfunctions.
Integrity checks are required in the prototype phase to prevent malfunctions due to disturbances in the supply voltage. This represents a major challenge to designers. The test system, which comprises an oscilloscope and probe, must have a low noise factor so that disturbances can be detected. The oscilloscope must provide a sufficiently large DC offset to make it possible to zoom closely into the signal. Finally, an input impedance on the oscilloscope of greater than 50 Ω is desirable in order that the oscilloscope does not represent an additional DC load on the test object.
The ideal tool to solve this issue is the N7020A power rail probe from Keysight Technologies. The probe has a DC offset range or +/- 24 V, which allows users to zoom closely into the AC component. So as not to disturb the DC supply voltage, the probe has an impedance of 50 kΩ for DC, which then drops off to a 50 Ω input impedance. The probe has a 1:1 attenuation ratio for frequencies above 1 MHz, which has a positive effect on the probe's inherent noise, and therefore also on the entire test system. To establish contact between the DC supply voltage and a p.c. board, an SMA cable and so-called pigtail cable are provided. These can be soldered directly onto the board.
This probe solution gives users the ideal tool for testing the integrity of a DC power supply on a p.c. board design. The test is essential in the prevention of malfunctions in the electronic circuitry during latter stages of the design and in the market launch phase.
- Bandwidth (-3 dB): 2 GHz
- Attenuation ratio: 1:1
- Offset range: +/- 24 V
- Input impedance @ DC: 50 kΩ
- Input dynamic range: +/- 850 mV
- Probe noise: 10 % of oscilloscope noise
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