Many companies’ purchasing will find that when they get the parts in the BOM provided by engineers to purchase materials, suppliers will often ask more carefully, otherwise they will not know what kind of materials to supply you. In serious cases, the purchased materials will not be used. Why is this the case? The problem is that many engineers who are not experienced enough have not completed the model of the device. The following is an example to illustrate what the complete device model is like.
The complete device model is generally composed of the main model, prefix, suffix, etc. General engineers only care about prefix and main model, but ignore suffix, even a few engineers even ignore prefix. Of course, not all devices must have prefixes and suffixes, but as long as this device has prefixes and suffixes, it cannot be ignored.
Device prefixes generally represent larger series of devices. For example, 74LS series in logic IC represents low power Schottky logic IC, 74ASL series represents advanced low power Schottky logic IC, 74ASL series has better performance than 74LS series. For example, 2N5551 triode and MMBT5551 triode are packaged differently, one is plug-in (TO-92) and the other is patch (SOT-23). If only 5551 triode is written on the BOM, then I definitely don’t know which one it is.
The phenomenon of ignoring prefixes is generally slightly less, but there are more cases of ignoring suffixes. In general, suffixes have the following uses:
1. Distinguish detailed performance
For example, the reset chip MAX706 of MAXIM company is 706, but there are several threshold voltages, for example, the threshold voltage of MAX706S is 2.93V, and the threshold voltage of MAX706T is 3.08V v. the suffixes “s” and “t” here represent different threshold voltages.
2. Distinguish between device grade and operating temperature
For example, TI’s reference voltage chip TL431, TL431C represents the operating temperature of the device is 0 to 70 degrees (civil grade), TL431I represents the operating temperature of the device is -40 to 85 degrees (industrial grade), wherein the suffixes “C” and “I” represent different operating temperatures.
3. Distinguish device packaging forms
For example, TI’s reference voltage chip TL431, TL431CP represents PDIP package, TL431CD represents SOIC package, wherein the suffixes “P” and “D” represent different packages (“C” represents temperature, which has been explained above).
4. Distinguish between ordering and packing methods
For example, if the TI company’s reference voltage chip TL431 CD is required to be purchased as a disc pack (2500PCS/ disc), then the order must be placed according to the model number of TL431 CDR. The suffix “R” here represents the disc pack. Otherwise, according to the TL431 CD order, buy back may be tube (75PCS/ tube) materials.
5. Distinguish between lead and lead-free
For example, ON’s comparator chip lm 393d (“d” means SOIC package). if you want to use a lead-free model, you must place an order according to LM393DG. the suffix “g” here means a lead-free model. if you don’t have this suffix, you have a lead model.
Suffixes may have other special uses, in short, the information of suffixes cannot be omitted, otherwise the purchased materials may not be what you want.
The prefixes and suffixes of different companies may be different (some prefixes and suffixes of a few companies are the same), which needs to refer to the specific conditions of actual manufacturers.