Electronic circuit ni hta, crystal oscillator ni gaw, aten ladaw npawt nhpang langai mi rai nga ai. Crystal oscillator hpe hkrak hkrak hpaw hpang lu na matu hte ngang grin ai hku bungli galaw lu na matu, circuit kata na shinggan na n-gun n-gun (load capacitance) (CL) hte maren hkrak hkra galaw ra ai. Capacitor hpe n hkrak ai hku shingdaw ai majaw, oscillation hta yak hkak ai lam, frequency n bung ai lam law wa ai, system n ngang grin ai lam ni pyi byin wa chye ai.
Ndai laika hta, crystal oscillator load capacitance a lachyum, shinggan capacitor ni a matu sawn la ai ladat, circuit hkrang shapraw ai shaloi tatut galaw mai ai lam ni hpe hkrak tup sawk sagawn na re.
Ⅰ. Crystal oscillator a load capacitance (CL) gaw kade daram rai kun?
Crystal galaw ai ni gaw, 18pF, 20pF, 12pF, etc. zawn re ai, datasheet hta, n-gun n-gun (CL) hpe masat da ma ai.Ndai gaw, n-gun n-gun (nominal load) hpe madi madun nna, n-gun n-gun (nominal oscillation frequency) hpe lu la na matu, n-gun n-gun hpe shadawn shadang tawn da ai.
Tsun mayu ai gaw, crystal oscillator gaw, CL hte maren sha re ai load capacitance hte maren sha rai yang she, hkrak ai frequency hpe shapraw lu ai.
Ⅱ. Shinggan na Load Capacitor ni gaw Load Capacitor hpe gara hku hkra machyi shangun ai kun?
Kalang lang na kristal oscillator circuit gaw lawu na zawn re ai hkrang hpe hkam la ai:
C1 hte C2 gaw lamu ga hte matut da ai shinggan capacitor lahkawng re (ga shadawn SMD capacitor ni);
XTAL a terminal lahkawng hpe crystal oscillator a pin lahkawng hte matut da ai;
Tatut hta, n-gun atsam CL a bung ai n-gun atsam hpe C1 hte C2 hku nna series hku nna dawdan ai, PCB hte package kaw nna shalawm ai parasitic atsam Cp hte hpawn.
Ⅲ. Lahta na jahpan: CL hpe madung tawn nna shinggan na Capacitor manu hpe gara hku chye na lu na kun?
Dai zawn re ai n-gun atsam (CL) a matu formula gaw lawu na hte maren rai nga ai.
Gara kaw rai:
C1, C2: Shinggan na capacitor ni hpe ga hte matut da ai;
Cp: PCB a nsam, shinggyin la ai lam ni hku nna shang wa ai Parasitic capacitance (ga shadawn 2pF kaw nna 5pF du hkra, shingdaw ai lam (sh) mahkrum madup hku nna sawn la mai ai);
CL: Crystal oscillator datasheet hta tsun da ai n-gun atsam hpe n-gun jaw ai lam.
【Ga shadawn】
Crystal masat masa hpe CL=18pF ngu sawn la nna, PCB a parasitic n-gun Cp ≈ 5pF ngu sawn la ga. C1 hte C2 a matu htap htuk ai manu ni hpe sawn la na matu:
Shawng nnan, manu ni hpe formula de galai bang u:
C1=C2=C ngu sawn la yang, formula hpe asan sha galaw ai:
Mahtai gaw:
✅ Dai majaw, shinggan na capacitor ni hpe hpaji jaw ai gaw: C1=C2=re.27pF (Madang manu).
Ⅳ. Hpa Majaw N Htap Htuk Ai Shinggan Capacitor Ni A Matu Manghkang Byin Ai Kun?
Frequency n bung ai: Shinggan na capacitor ni grai kaji ai (sh) grai kaba ai rai yang, crystal gaw shi a nominal frequency kaw na n bung ai majaw, system clock shut mat na re.
Start-up yak hkak ai lam (sh) n ngang kang ai lam: Grai law hkra n-gun dat ai majaw gain hpe shayawm kau ya ai majaw, crystal hpe n-gun n-jaw lu ai (sh) frequency jitter hpe hkam sha lu ai.
N-gun jai lang ai lam law wa ai: N kaja ai hku n-gun dat ai majaw, crystal oscillator circuit hta n-gun jai lang ai lam grau law wa ai.
EMI jat wa ai: N grin ai oscillations ni gaw n teng n man ai frequency ni hpe shabyin ya lu nna, system a wan n-gun n-gun (EMC) hpe hkra machyi shangun ai.
V. Design hpaji jaw ai lam ni hte Engineering galaw ai lam ni
Dai hpe atsawm sha bai maram yu u.
CL manu hpe dawdan u.
Hpaji jaw da ai circuit topology hpe chye na na.
Shinggan capacitor manu ni a range hpe hpaji jaw ai kun ngu ai hpe yu yu ga.
2. Board makau grup yin hpe teng sha myit yu ga .
PCB simulation (sh) mahkrum madup hpe lang nna Cp hpe sawn shapraw u.
-lawan ai (sh) hkrak ai ahkying ni a matu (ga shadawn, matut mahkai ladat ni, MCU main frequency > 100MHz), hkrak ai hku sawn la ai (sh) chyam dinglik ai lam hpe galaw na matu hpaji jaw da ai.
3. Hkrang bung ai capacitor ni hpe lang u
Madung hku nna C1=C2 hpe frequency hpe center galaw nna balance galaw na matu hpaji jaw da ai.
Asymmetrical design hpe laksan shingdaw ra ai lam ni a matu mung lang mai ai.
4. Debugging galaw na matu SMD capacitor array hpe lang u
SMD capacitor ni hpe (ga shadawn, 10pF, 15pF, 22pF, 27pF, etc.) chyam yu nna, hkrak ai hpe tam na;
Spectrum analyzer (sh) oscilloscope lang nna pru wa ai n-gun atsam hte n-gun atsam hkrak ai lam hpe jep yu u.
6,Law malawngFAQ
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Ga San ni |
Mahtai ni |
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CL=12pF rai yang, shinggan na capacitor ni gaw gara hku manu dan ra ai kun? |
Cp{0}}pF rai yang,C2≈14pF rai na re. |
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Hpa majaw MCU nkau mi hta shinggan na capacitor n ra ai kun? |
Nkau crystal oscillator circuit ni hta -load capacitor ni hpe bang da ai (ga shadawn, STM32), dai majaw shinggan na capacitor ni n ra ai. |
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N htap htuk ai shinggan capacitor ni gaw, kristal oscillator hpe hkra machyi shangun lu na kun? |
Kaja wa nga yang, shanhte gaw wan nat, n jahten kau na re, raitim, startup hkrat sum ai (sh) frequency error byin shangun chye ai. |
Daw dan lam
Crystal oscillator a matu shinggan load capacitor ni a hkrang shapraw ai lam gaw kaji tim ahkyak ai lam langai rai nna, aten ladaw masa a ngang grin ai lam hte hkrak ai lam hpe hkrak hkra hkra machyi shangun ai. CL hte C1/C2 lapran na jahpan matut mahkai lam hpe chye na nna, PCB parasitic capacitance majing hpe madung tawn nna parameter ni hpe gram lajang ai gaw, kam mai ai oscillation hte hkrak tup ai frequency hpe lu la na matu ahkyak ai lam rai nga ai.
Hpa majaw nga yang, grai lawan ai digital system ni, matut mahkai jak ni, shing nrai, grai ra kadawn ai aten ladaw ni hpe lang ai system ni hta, crystal oscillator a load capacitance hpe hkrak lata la nna, shingdaw ai lam gaw, grai ahkyak la ra ai engineering bungli langai rai nga ai.
HCIshaning jan mahkrum madup nga ai hpaji ninghkring laboratory hte application engineer hpung langai mi nga ai, manu jahpu n jaw ra ai sha hpaji ninghkring ni hpe shingdaw nna chyam dinglik ai lam ni hpe galaw ya nga ai. Ndai lam hte seng nna ra kadawn ai lam ni nga yang, anhte a dut mari (sh) hpaji ninghkring ni hpe matut mahkai mai ai.