Uma kuqhathaniswa ne-LDO, umjikelezo we-DC-DC uyinkimbinkimbi kakhulu futhi unomsindo, futhi izidingo zesakhiwo nesakhiwo ziphezulu. Izinga lesakhiwo lithinta ngqo ukusebenza kwe-DC-DC, ngakho-ke kubaluleke kakhulu ukuqonda ukwakheka kwe-DC-DC
1. Isakhiwo esibi
● I-EMI, iphinikhodi ye-DC-DC SW izoba ne-dv/dt ephezulu, uma kuqhathaniswa ne-dv/dt ephezulu izobangela ukuphazamiseka kwe-EMI okukhulu kakhulu;
● Umsindo ophansi, umugqa ophansi awulungile, uzokhipha umsindo omkhulu ngokuqhathaniswa ocingweni lwaphansi, futhi le misindo izothinta ezinye izingxenye zesekethe;
●Ukwehla kwamandla kagesi kukhiqizwa kuzintambo. Uma i-wiring yinde kakhulu, ukwehla kwamandla kagesi kuzokhiqizwa ku-wiring, futhi ukusebenza kahle kwayo yonke i-DC-DC kuzoncishiswa.
2. Izimiso ezijwayelekile
● Shintsha isekethe yamanje enkulu ibe mfushane ngangokunokwenzeka;
●Indawo yesiginali kanye nomhlabathi wamanje ophezulu (indawo yamandla) ihanjiswa ngokuhlukana futhi ixhunywe endaweni eyodwa ku-chip GND.
①Iluphu yokushintsha emfushane
I-LOOP1 ebomvu emfanekisweni ongezansi yindlela yokugeleza kwamanje lapho ipayipi le-DC-DC high-side livuliwe futhi ipayipi elihlangothini eliphansi livaliwe. I-LOOP2 eluhlaza iyisiqondiso sokugeleza kwamanje lapho ipayipi lehlangothini eliphezulu livaliwe futhi ipayipi elihlangothini eliphansi livuliwe;
Ukuze wenze amalophu amabili abe mancane ngangokunokwenzeka futhi wethule ukuphazamiseka okuncane, le migomo elandelayo idinga ukulandelwa:
●I-inductance eseduze nephinikhodi ye-SW ngangokunokwenzeka;
● Amandla okufaka aseduze nephinikhodi ye-VIN ngangokunokwenzeka;
●Umhlabathi wama-capacitor okokufaka nawokukhipha kufanele ube seduze nephinikhodi ye-PGND.
●Sebenzisa indlela yokubeka ucingo lwethusi;
Kungani ungenza lokho?
● Ulayini omuhle kakhulu futhi omude kakhulu uzokhuphula i-impedance, futhi i-current enkulu izokhiqiza i-voltage ephezulu kakhulu ye-ripple kule impedance enkulu;
●Intambo encane kakhulu futhi ende kakhulu izokhuphula i-parasitic inductance, futhi umsindo weswishi yokuhlanganisa ku-inductance uzothinta ukuzinza kwe-DC-DC futhi kubangele izinkinga ze-EMI.
● Amandla e-parasitic kanye ne-impedance kuzokhuphula ukulahleka kokushintsha kanye nokulahleka kokuvala futhi kuthinte ukusebenza kahle kwe-DC-DC
②ukubekwa phansi kwephoyinti elilodwa
Isisekelo sephoyinti elilodwa sibhekisela endaweni eyodwa phakathi kwesignali nendawo yamandla. Kuzoba nomsindo omkhulu uma kuqhathaniswa endaweni yamandla, ngakho-ke kuyadingeka ukugwema ukubangela ukuphazamiseka kumasignali amancane azwelayo, njengephinikhodi yempendulo ye-FB.
● Umhlabathi wamanje: L, Cin, Cout, Cboot xhuma kunethiwekhi yendawo yamanje ephezulu;
● Indawo yamanje ephansi: I-Css, i-Rfb1, i-Rfb2 ixhumeke ngokuhlukene kunethiwekhi yesignali yomhlabathi;
Okulandelayo ukwakheka kwebhodi lokuthuthukisa le-TI. Okubomvu kuyindlela yamanje lapho kuvulwa ithubhu eliphezulu, futhi indlela eluhlaza okwesibhakabhaka yindlela yamanje lapho kuvulwa ithubhu eliphansi. Isakhiwo esilandelayo sinezinzuzo ezilandelayo:
●I-GND ye-input capacitor ne-output capacitor ixhunywe ngethusi. Lapho ufaka izingcezu, umhlabathi walokhu kokubili kufanele uhlanganiswe ngangokunokwenzeka.
● Indlela yamanje ye-Dc-Dc-ton ne-Toff imfushane kakhulu;
●Isiginali encane engakwesokudla iyiphoyinti elilodwa eliphansi, elikude kakhulu nethonya lomsindo omkhulu weswishi wamanje kwesokunxele;
3. Izibonelo
Isakhiwo sesekhethi ye-DC-DC BUCK evamile inikezwe ngezansi, futhi amaphuzu alandelayo anikezwe ku-SPEC:
● Ama-capacitor okokufaka, amashubhu e-MOS anomkhawulo ophezulu, nama-diode akha ama-loop ashintshayo amancane futhi amafushane ngangokunokwenzeka;
●Ikhono lokokufaka eliseduze ngangokunokwenzeka kuphinikhodi ye-Vin;
●Qinisekisa ukuthi lonke uxhumo lwempendulo lufushane futhi luqondile, nokuthi izinqamuleli zempendulo nezinto ezinxephezelayo ziseduze ne-chip ngangokunokwenzeka;
●SW kude namasiginali azwelayo afana ne-FB;
●Xhuma i-VIN, SW, futhi ikakhulukazi i-GND ngokuhlukana endaweni enkulu yethusi ukuze upholise chip futhi uthuthukise ukusebenza okushisayo nokuthembeka kwesikhathi eside;
4. Fingqa
ukwakheka kwesekethe ye-DC-DC kubaluleke kakhulu, okuthinta ngqo ukuzinza nokusebenza kwe-DC-DC. Ngokuvamile, i-SPEC ye-DC-DC chip izonikeza isiqondiso sesakhiwo, esingabhekiselwa kuso ukuze siklanywe.