![]() To obtain good and reliable measurement values, the user should take a few basic precautions on how the measurements are made. Table 3.1 shows a typical a measurement matrix setup. To quickly and efficiently characterise a converter and check the validity of the datasheet, it is often worthwhile to use a measurement matrix where the various combinations of load and input voltage can be compared. For example, datasheets do not usually give efficiency vs operating temperature graphs (although RECOM can supply such detailed information on request).Īs already mentioned, the electrical behavior of a DC / DC converter is determined by many different parameters that are specified in the data sheet. In many cases, it is necessary for the customer to measure the critical specifications of concern themselves using the actual or anticipated operating conditions of the application. Additional filter components may be in some cases necessary in order to get a reliable, repeatable measurement, but the customer should be aware that the way the measurement is made affects the measured value and a comparison between two converter specifications can only be done if both are known. A converter with 50mVp-p is better than one with 100mVp-p, right? Well not if the fine print at the back of the datasheet states that the first converter measurement was made with a 47μF electrolytic in parallel with a 0.1μF MLCC across the output pins to additionally filter the output and the second converter specification was made without any external components. A classic example is the output ripple and noise specification, usually given in millivolts peak-to-peak (mVp-p). Similarly a converter with a reliability specification of 1 million hours according to MIL-HDBK-217E is not necessarily more reliable than a converter with a reliability specification of “only” 800 thousand hours according to MIL-HDBK-217F or another converter with “only” 400 thousand hours according to Bellcore/Telcordia.Īn unscrupulous manufacturer can use this lack of standardisation to present their product in a better light. This means a load regulation specification of ±5% for a load range of 10% - 100% is not necessarily worse than a rival converter with a load regulation specification of ☓% for a load range of 20% - 100%. ![]() ![]() But there are no agreed standards between manufacturers over the parameter fixing, so some will specify a regulation value for the whole 0% - 100% load range, others for 10% - 100% and still others for 20% - 80% load. For example, a load regulation figure will be made with nominal input voltage, 25☌ ambient temperature and be valid over a specified load range. The problem is that many of the specifications are inter-related so some parameter fixing is needed, i.e, that specific values such as the ambient temperature or input voltage are kept constant during the measurement of the performance specification of interest. Every respectable manufacturer supplies a technical datasheet with their product that details at the very least the basic operating parameters, overall dimensions and pin connections, but to compare one DC/DC converter with another just relying on the datasheet information often requires interpretation rather than just a simple comparison of numbers. ![]()
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