Embedded the systematic level chip of the core technology that hardware design will make 21 centuries microelectronics (the 3 old crucial techniques in SoC) design and domain of mutual and shirt-sleeve a few research were done elaborate in detail, the challenge that faces to SoC design and development trend undertook expectation.

 

Control plate of some electric machinery contains the function that motivation reclaims, when aiding power cell, the roll of electric machinery also can continue to be control plate power supply. And the voltage that the generation of inhomogenous rotational meeting of electric machinery fluctuates quickly, cause power source chip thereby the voltage with output not stable pole, the fluctuation report with frequent inside cutty time equipment of the class after making, bring about the blue tooth module on bat to lose firmware often to burn out even, reduced product performance. Bring relevant configuration of the foot through adjusting EN of power source chip later, perfect solved this problem. Want to knew to ” of what “ hands or feet do to EN? Is small EN returned accumulate what kind of great wisdom containing?

 

One, overview

EN namely Enable, namely “ makes can the meaning of ” , of different chip call a law to also differ somewhat, wait like EA, RUN. And their function is basic it is same, when having this activation that cite a base only namely, chip or module ability are outputted normally. Be aimed at this one function, we can add a few simple periphery circuit to realize stable chip to perhaps output the function of electrify sort. The EN of a few more advanced power source chip brings a foot to still contain the character that sluggish answers normally.

 

2, use skill

1. approachs resistance with cent opportunely, realize the stable output of power source chip

To power source chip, we use cent to press resistor to receive EN signal the input of power source to bring a foot to go up normally, the voltage that will prevent EN to carry exceeds its compression value. And the condition is worth to fall in contented compression, be in the voltage set of EN foot even the limits of “ appropriate ” .

 

For example the article mentions at the beginning, the 24V power source of control plate of some electric machinery is in electric machinery power supply while also pass DC/DC:MP2451 outputs 12V to give other circuit power supply. When aiding power cell, electric machinery generates electricity for control plate power supply, and the roll of electric machinery is not is divide evenly fast, produced the tension with bigger wave motion, following graphs are shown 1 times, maize line generates electricity reversely for electric machinery voltage, green is the voltage that MP2451 outputs.

 

Graph 1 electric machinery generates electricity the output curve of curve and DCDC

 

By on graph 1 can see, of electric machinery generate electricity voltage (the input voltage of DC/DC) VIN makes in 6.2V moment probably can DC/DC output, the 12V that inputs voltage to be less than set right now outputs voltage, the action that the canal feedbacks as a result of output is in the MOS that makes DC/DC in-house to guide quickly all the time connect and shut, those who formed a noise to wrap subsidiary channels in the human body through which vital energy to fluctuate as the input, not stable output voltage. When electric machinery generate electricity when voltage is more than 12V, DC/DC just outputted smooth 12V voltage.

 

Because the cent in circuit controls resistor network,this is the setting is undeserved, inputting the threshold value voltage that EN achieved when voltage is very low, bring about make prematurely can output of power source chip. This is designed namely considered to bring the EN of power source chip crural voltage setting to be under compression value only in the process, and did not consider to approach the cent of EN foot network set to be in the example of the limits of “ appropriate ” .

 

So does the cent of EN foot press network set to in what position be compared appropriate?

 

Graph 2EN makes can output a curve

 

L is shown like curvilinear ① place, make with respect to what achieved VEN when input voltage is inferior can threshold value, make can chip output, the influence that right now output is inputted wave motion and electrify is slow, the working stability; of circuit of the class after was being affected

 

L is shown like curvilinear ② place, when input voltage VIN rises to 70%~80% , VEN just arrives make can threshold value, right now chip output renounced the not stable phase that inputs power source, electrify is rapid, output is smooth, reduced the influence; that inputs voltage wave motion

 

L at the same time obligate the problem; that the surplus of 20%~30% avoided to input power source wave motion to bring about output to shut

 

L from this knowable the voltage of EN threshold value power source chip presses network set to be in through cent 70%~80%×VIN is relatively reasonable, EN threshold value can be checked through chip manual. Following graphs are shown 3 times, according to foregone EN threshold value and input voltage can get appropriate cent to press resistor scale.

 

Graph the EN threshold value with 3 foregone basises allocates network resistor

 

Graph 4 it is the output weaveform after the cent that adjusts EN to cite a base presses resistor block to be worth, the voltage wave motion of output got clear improvement. Continue to adjust cent to control resistor block cost again, can get more smooth output weaveform, the settlement with this simple and effective method in front the problem with mentioned not stable output.

 

Graph the 4 voltage after adjusting cent to approach resistance are undee

 

This shows, small EN cites a base, the setting is undeserved also can cause not little trouble, be worth in contented EN compression accordingly below, the input of EN according to actual condition voltage stability is in the limits of “ appropriate ” , also be very important. This little use skill, did you learn?

 

2. uses EN function opportunely, realize electrify sequential

In circuit design, chip or module often need a variety of job power supply, also raised corresponding requirement to the electrify order of these power source at the same time. If did not satisfy the requirement of these electrify sequential,the likelihood causes the trouble such as latch of bus line conflict, parts of an apparatus. For example the working power source on some system has VCC_Core, VCC_DDR, VCC_DIO 3 kinds of power source, the power source chip through schism is controlled. The RC return that can cite a base through adjusting EN of power source chip right now will control electrify sequential, the R1 in pursueing namely and C1.

 

Circuit of delay time of graph 5 RC

 

The defer of movement of sure also generation with RC time big constant, namely hind begin the work, change different parameter to get different delay time time, control the electrify sequential of chip of schism power source thereby. This law still can satisfy what dominate chip of many power source with an EN signal to use requirement.

 

Need the resistor in noticing is RC to also cannot pass big, want to satisfy EN to cite the voltaic demand that crural place needs. Following plan institute show the EN in be manual of chip of some power source to input voltaic condition.

 

Foot of graph 6 EN inputs voltaic citing

 

3, summary

Pass the control to EN, can realize corresponding function, include the static job feature of reasonable setting EN, can avoid not to stabilize power supply of power source of level open chip in power source voltage already, can avoid to be when regular job again, wave motion of power source voltage causes systematic accident to drop report. Pass the logistic sequential control to EN, can realize the control of sequential of electrify of multichannel power source.

 

In addition, in EN end adds proper control circuitry, can magnify the sluggish wire back of EN is pressed. This system to batteries power supply, when batteries is adjacent and extinct, can avoid circuit to repeat fluctuation report circularly.

 

This shows, this looks be like simple EN to cite a base, when using, also need to add an attention more. Pass the introduction of the article, you also feel this is small EN, accumulate contain greatly wisdom?