In project practice, changed a parts of an apparatus with be updated better, have smaller voltaic loss. The result malfunctions instead, new parts of an apparatus or appliance even burn down. Still have this kind of operation? Why? Linear manostat is quite simple parts of an apparatus, do not have too much challenge. Nevertheless, still can be to be able to encounter a trouble now and then.

 

Abhinay Patil is becoming field application engineer when, sometimes the client can ask him to recommend the parts of an apparatus that replaces other vendor. Below a lot of circumstances, of parts of an apparatus replace by the client’s production, purchase group decision, and original circuit stylist may be not witting this change. Decision-making process is quite simple: Replace parts of an apparatus to ought to have same function, enclose and bring crural configuration, and as coequal as the parts of an apparatus that be replaced better even electric norms. Should satisfy only all these requirements, with respect to Xiangyuan engineer of parts of an apparatus is offerred compare data necessarily, will new yuan of parts of an apparatus in adding material detailed account, regard the 2nd supplier as equipment options. Finish these, ought to success. But in fact, after the product that uses old parts of an apparatus to work normally is replacing the options that it is equipment, invalidation begins on product line. Where to make mistake?

 

Abhinay Patil states he ever participated in at this moment settle a such case: Follow afore-mentioned technological process, in client design, segregation type RS-485 is sent and receive implement the 2nd supplier that regards another supplier as parts of an apparatus. Appearance of two parts of an apparatus, dimension and function are compatible, and parts of an apparatus has better electric norms. The client issued the order of a large number of this parts of an apparatus subsequently, appear to make mistake without any reason. However, client report says, new RS-485 is sent and receive implement invalidation begins on manufacturing testboard. Because there are any other changes in the design, it is the new parts of an apparatus or appliance in the graph made mistake certainly so.

 

Through further investigation, ability discovery: To send and receive implement the linear manostat of power supply of bus line side was not pressed anticipate stabilized voltage comes 5 V, rise to taller voltage however. Accordingly must microscope, older send and receive implement the data manual with refill-unit, and the data manual of linear manostat, in order to decide where made mistake.

 

“ is better ” is a qualitative term, specific depend on the parameter of place discussion. For example, when involving speed, CMRR, PSRR, had jumped over higher; When involving maladjusted voltage, drift, lower better; And it is better that you do not need knowledge of too much project to know power comsumption always is lower. Be really such? In this special case, be not such. Old send and receive implement model of 15 MA (is used up to be worth in bus line side below unused condition) electric current, and new parts of an apparatus or appliance uses up) of maximum of 2 MA (only. Without doubt, new parts of an apparatus or appliance looks better on data. Unfortunate is, linear manostat appears wrong.

 

Graph 1. The example of the smallest load current in data manual

 

Article begin mentions no less than, linear manostat is quite simple, do not have too much requirement. However, a its special requirement is to need ability of the smallest load current to work normally. If this one demand was not satisfied, manostat will not normal stabilized voltage, output voltage exceeds range. If the inputs voltage outclass expectation output voltage of manostat, the circumstance will become poorer.

 

Graph 2. Left circuitry pursues: The manostat that uses old parts of an apparatus works normally (requirement of contented the smallest load current)

 

Right circuitry pursues: The manostat that uses new parts of an apparatus or appliance is not stable (load current is not worth T)

 

A lot of contemporary and linear manostat are special in the design noted this problem, won’t produce breakdown consequently. A few old parts of an apparatus (if the client in this case designs uses parts of an apparatus) did not consider this a little bit, because this is when systematic design,need additional precautionary measures. Below certain circumstance, adjustable the feedback resistor network that outputs LDO is in charge of the smallest load current. Unfortunate is, if decide to increase resistance considerably, hold same specific value at the same time, get into trouble probably inadvertently. Still have additionally one kind of case, satisfy laden requirement during regular job by the parts of an apparatus of LDO power supply namely, and in bide one’s time be no good below condition. These are the potential defect that need an attention, because this is sure to read LDO data manual carefully please. If have demand of the smallest load current, come out now with substance of some kind of form normally. A few give typical examples are below:

 

Graph 3. After increasing resistor of a release to satisfy the smallest load current to ask, the problem was solved

 

The End

Accordingly, once knew the prime cause that the problem arises, so repair is quite simple. What place should do is in adjuster output end adds resistance of a release, in order to use up the smallest load current. Although not sensible client is very easy,ascribe the problem to simply parts of an apparatus, but the client in this exemple saw positive one side, very glad to can study new technology from inside this one case.