DC-DC module power supply ripple measurement summary scheme
2022-08-16

The key is to confirm the cleanliness of the power module, which requires accurate measurement of the output ripple of the dc-dc power module. 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. This is mainly caused by the error of the measurement method.


dc-dc power module ripple measurement method:


1. The bandwidth of the oscilloscope is required to be 20MHz (most low-end oscilloscope gears are limited to 20MHz, and good products also have a choice of 200MHz bandwidth control), the purpose is to prevent the high-frequency noise of the digital circuit from harming the precise measurement of ripple, and to ensure accurate measurement as much as possible accuracy;


2. Set the coupling method as communication and AC coupling, convenient and accurate measurement (observe the ripple carefully with a smaller gear, and do not pay attention to the AC level);


3. Make sure that the camera grounding device is as short as possible (the key reason why the measurement ripple is more than 100 mV is that the wire connector is too long), and the original detection short needle built into the probe should be used as much as possible. If you test short pins, you can disassemble the probe's wire connector and shell, expose the camera shell, and make a self-made grounding wire coiled on the probe shell to ensure that the length of the wire connector is less than 1cm;


4. The ground of the oscilloscope is suspended, only the ground of the probe and the reference point of the test data signal are common, and there is no need to share the ground with the test bench according to other methods (that will introduce a large ground noise to the ripple measurement). For example: when the oscilloscope and other instruments share a plug-in board, the power switch of other instruments may generate noise interference signals for the test through the ground wire.