Comparing Taiyo Yuden’s NRS 4018 and Vishay’s IFSC 1515 Series
Finding a drop-in replacement inductor for an already-finished design can be a risky and time-consuming process. Risky because the product datasheet doesn’t always reflect the true performance of the part, and time-consuming because true validation of the replacement inductor often involves in-house lab testing. Some manufacturers have tried to reduce the risk and time requirements of this process by offering cross-reference tools and PDFs on their website. However, their tools often have one of the same limitations: their cross-references are not backed by lab testing and comparison at all operating points, so it is still up to the customer to validate the recommended parts themselves. Recently, SourcingBot has released their cross-referencing tool which finds replacements across all manufacturers and provides lab-measured data to help engineers verify replacement parts. In this article, we will look at two popular series of SMD inductors from Taiyo Yuden and Vishay, show the traditional method of cross-referencing, introduce a technique to make the method more robust, and finally look at SourcingBot’s tool, which can present reliable and valid inductor cross-references at lightning speed.Comparing Datasheet Values of Fixed Inductors
The traditional method of cross-referencing is done by comparing the datasheet parameters of both parts. Typically, this must be done manually since there are many parameters such as rated current or saturation current which are guaranteed at given operating conditions, which are only found in the datasheet. SourcingBot presents both datasheet parameters and measurement conditions on their part page and comparison table, saving engineers a trip to each datasheet to see if the rated current was measured at 20 degrees change or 40, for example.Here we will examine the Taiyo Yuden NRS4018T100MDGJV (NRS 4018 Series) and the Vishay IFSC1515AHER100M01 (IFSC 1515 Series). To verify a drop-in replacement, both the electrical and mechanical properties of the two parts must be similar. The footprint dimensions of the two parts are the same, at 4x4mm, and their height parameters differ by 0.1mm, at 1.8mm (Taiyo Yuden) and 1.9mm (Vishay). Both parts are shielded and feature DC resistance specifications of 150mOhm (Taiyo Yuden) and 170mOhm (Vishay). They feature 10uH nominal inductance at 100kHz and 1.2A (Taiyo Yuden) and 1.3A (Vishay) saturation current, specified at a 30% inductance drop. The Taiyo Yuden part is AEC-Q200 rated, which is important for automotive applications. Both parts have 20% tolerance on nominal inductance.
Comparing the datasheet parameters of both parts, it appears that they would be good drop-in replacements for one another, excluding automotive applications. This is where a typical cross-reference ends with the conclusion that the two parts could be compatible with each other. This analysis does not, however, confirm with 100% certainty that these two parts will work in place of one another.
Operating Point Analysis of Fixed Inductors
A comparison of datasheet values is a good starting point for cross-referencing, but it does not answer one important question: How do these parts perform at the operating current and frequency at which they will be used? In the past, this type of analysis has been extremely time consuming or simply ignored, since the operating point behavior of parts needed to be measured manually or (if you’re lucky) found on the manufacturer’s website. If these characteristic charts are available for each part, the two graphs must be compared by eye, which is challenging considering the different scales and measurement conditions used by different manufacturers.Today, operating point analysis can be done simply and for free using the chart comparison tools at SourcingBot. Their engineers have collected and compared lab-measured data for fixed inductors and other passive components so that they can be easily compared across datasheet values and operating points. If we search for our two inductors in their database, we can easily check the impedance and inductance against frequency, as well as the saturation and temperature rise curves. This is where we can verify if our two inductors will perform the same at our intended operating point.
Here we can see that the nominal inductance given in the datasheet is not always exactly what you get. The Taiyo Yuden inductor measures in at less than 10uH (still within tolerance) while the Vishay part starts with more than the nominal inductance. However, depending on the operating conditions, the Taiyo Yuden inductor could be preferable because of its relative stability compared to the Vishay part.
The temperature curves show that both parts exceed their rated current specification and should perform similarly in a thermal sense.
Looking at impedance vs. frequency, we can see that the Taiyo Yuden part will remain inductive at operating frequencies about 10MHz higher than the Vishay part. This is likely due to the smaller inductance value we saw in the L vs I characteristic chart.
Automating the Inductor Cross-Referencing Process with SourcingBot
In this article, we have seen that all cross-references are not made equal. At certain operating points, the two inductors do not perform the same, meaning that deeper analysis is required to guarantee compatibility. This entire process has been automated by the engineers at SourcingBot to speed up your product development and strengthen your supply chain. Their website automatically performs the first step of cross referencing, the datasheet comparison, and presents a list of the most similar parts.
Depending on the requirement of your cross-reference different parts can be found, for example those with higher rated current, at the click of a button. Within the comparison table, it is simple to compare the performance at your operating point with their “Click to Compare” button. In addition, lab-measured parameters are compared to the datasheet parameters in an easy-to-read table for each part.
To try the SourcingBot cross-referencing and comparison tools, visit their website at sourcingbot.com and start finding parts!
