Power supply interference immunity designs individual's understanding

Power supply interference immunity designs individual's understanding

—— YongHao electron hardware development department Wang chun qing

        Along with YongHao electron Uni-card System product 's continual get rid of the stale and bring forth the fresh, I and my develop troop will continual will we develop process in accumulate 's technical matter, Settles scheme and program composition individual's understanding with everybody share.

        Starts up a hardware development project, Wants full consider go whole system architecture, Application's function accomplish, Systematic subdivides ability 's promote and so on. So, Ases a hardware systematic designer, Will know each aspect's requirement, And synthesize rise, Brings up appropriater hardware settle scheme. So, At develops bring processor's electron product time, How enhance anti-interference ability and electromagnetism consist with sex, Then equivalent to important.

        Fors example YongHao electron run near 6 year 's Public Transportation POS system, Along with market's change, We at inhere a again upgrade on product, Goes today 's 6.0 versions; Already has was add GPS, GPRS, VCR waits for modular all function product. So, Power supply part again also can not like at first version that —— use common linear step down 's certain press administer LM2940 then can ensure normal supply electricity. Example: A GPRS communication module can reach 2A at modes operation time peak inrush current. Power supply is ensure hardware system normal working basis, Designs in want detailed analysis: Systematic is able to supply 's power supply Enter; Single board need bring forth 's power supply exportation; Each power supply need supply 's current size; Electric power-supply circuit efficiency; Each power supply be able to Permission 's fluctuate range; Whole power-supply system requisite electrified order and so on. Alsoes want consider cost control, For example pick up: Uses switching power supply chip, Cost high and disturbs big.

        Some systems want especial pay attention to resist electro-magnetic interference: ( 1) Micro controller clock frequency especial high, Bus cycle especial rapid system. ( 2) Systematic include high-power, Big current drive circuit, Is like I department 's GPRS/ CDMA mass transportation system. ( 3) Contains faint analog signal circuit and high accuracy A/ D changes circuit's system.

        Is increase systematic resist electro-magnetic interference ability, Adopt frequence low micro controller can effective reduce noise and enhance systematic anti-interference ability. Same frequence's side wave and pure wave, 's frequent ingredient than pure wave many many in a side wave. Though a side wave's frequent ingredient's wave's extent, Than fundamental wave small, But frequence more high more easy shoot come out become noise source, Micro controller brings forth 's influentialer high-frequency noise big about is clock frequency 's 3 time. Micro controller chief adopts high-speed CMOS technology manufacture. Signal input holds quiescent state incoming current at about 1mA, Input capacitance about 10PF, Input impedance equivalents to high, High-speed CMOS circuit 's exports hold all have corresponding bring carry ability, Thats be equivalent to big exportation value, Will be a door 's export hold by a section very long lines draw go input impedance equivalent to high Enter hold, Reflects problem very serious, It will cause signal distortion, Increases system noise. Must consider signal reflection, Impedance matches wait for problem. Meanwhile signal at prints 's delayed time and draw linear characteristic impedance relevance on board, Thats be with print bread board material's dielectric relevance.

        Can rough field think, Signal at prints board draw linear Transmission speed, Abouts for velocity of light 's 1/3 go 1/2 between. At prints on bread board, Signal by a 7W 's resistance and a section 25cm long down-lead, Online delays time approximate between at 4~20ns. This be to say, Signal 's down-lead more short more good on printed wire, Most long should not exceed 25cm. And hole number also should try the best little, Had better not precious sight more 2.

        Uses as draw a conlusion generalize printed substrate design 's a rule: Signal transmission on printing plate, It delayed time not should be more than use part of an apparatus or appliance 's mark state delay time. Will say use good go ou capacitance, Groupware disposal reasonableness, Prints circuit board all very critical.

        From technical point of view, Each designs finally all can do out, But a project 's successful or not, Not only will lie on technically 's accomplish, Alsoes with product's quality have very big relation.

        Above for oneself some superficial experience, Looks everybody same profession criticise correct, Will encourage mutual encouragement; Unremitting 's study and accumulate, Talents make a hardware design personnel go on continual progress.

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