The dc-dc power module ripple index value is a very important main parameter. A clean power module is the primary condition for the smooth operation of digital circuits, and it is also a vital guarantee for the various main parameters of simulated analog electronic components.

The key is to confirm that the power module is clean, and accurate measurement of the output ripple of the dc-dc power module is required. However, the ripple value obtained by many people's accurate measurement is hundreds of mV or even hundreds of mV, which is far higher than the larger ripple value issued by the component guide. The key is that the measurement method is wrong.dc-dc power module ripple measurement method:1. The oscilloscope bandwidth is required to be 20MHz (most middle and low-end oscilloscope gears are limited to 20MHz, and good products also have 200MHz bandwidth control options), the purpose is to prevent the high-frequency noise of digital circuits from harming accurate ripple measurement and ensure accurate measurement as much as possible Accuracy2. Set the coupling method to communication and AC coupling, which is convenient and accurate measurement (use a smaller gear to carefully observe the ripple, and do not pay attention to the AC level);

3. Ensure that the camera grounding device is as short as possible (the key reason for the measurement ripple of hundreds of mV is that the wire connector is too long), and use the original detection short needle built in the probe as much as possible. If you are testing short needles, you can remove the wire connector and shell of the probe, expose the camera shell, and wind your self-made ground wire on the probe shell to ensure that the length of the wire connector is less than 1cm;

4. The oscilloscope ground is suspended. It is only based on the common ground of the probe ground and the reference point of the detected data signal, and it is not necessary to use the common ground with the test bench according to other methods (that will introduce greater ground noise to the ripple measurement). For example: when the oscilloscope and other instruments share the power strip, the power switch of other instruments may generate noise and interference signals for the test through the ground wire.