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SMD Tuning Fork Crystal PSX1610 Features Ultra miniature SMD tuning fork crystal resonator A ceramic package with metal lid providing high precision and reliability. Metal lid connected to GND terminal to reduce EMI Suitable for mobile communications and consumer devices. Applications Mobile communications and consumer devices, etc. Smart card and Wearable devices More
SMD Tuning Fork Crystal PSX215 Features Ultra miniature SMD tuning fork crystal resonator A ceramic package with metal lid providing high precision and reliability. Metal lid connected to GND terminal to reduce EMI Suitable for mobile communications and consumer devices. Applications Mobile communications and consumer devices, etc. Smart card and Wearable devices More
3215mm with10ppm Features 3215 Size Miniature And Fork Crystal Resonator With A Low Profile Pf 0.75mm. A Ceramic Package Providing High Precision And Reliability. Metal Lid Connected To GND Terminal To Reduce EMI. Noise Resistance Application (Smart Meter Etc.) series resistance 50KΩ max available. AEC-Q200 Compliant Applications Mobile Communications, PDA, Wave Clock, Digital Appliance Auto Motive Applications Such As Multimedia Device More
SMD Tuning Fork Crystal PSX415 Features 4115 size miniature and fork crystal resonator with a low profile pf 0.75mm. a ceramic package providing high precision and reliability. metal lid connected to GND terminal to reduce EMI. Noise Resistance application (smart meter etc.) AEC-Q200 compliant Applications mobile Communications, PDA, wave clock, digital appliance auto motive applications such as multimedia device More
SMD Tuning Fork Crystal PMX145 Features Ultra Miniature SMD Tuning Fork Crystal Resonator Plastic molded SMD tuning fork crystal of heat-resistance Metal Lid Connected To GND Terminal To Reduce EMI Suitable For Mobile Communications And Consumer Devices. Applications Mobile Communications And Consumer Devices, Etc. Smart Card And Wearable Devices More
SMD Tuning Fork Crystal PMX206 Features Ultra Miniature SMD Tuning Fork Crystal Resonator Plastic molded SMD tuning fork crystal of heat-resistance Metal Lid Connected To GND Terminal To Reduce EMI Suitable For Mobile Communications And Consumer Devices. Applications Mobile Communications And Consumer Devices, Etc. Smart Card And Wearable Devices More
SMD Tuning Fork Crystal PMX405 Features Ultra Miniature SMD Tuning Fork Crystal Resonator Plastic molded SMD tuning fork crystal of heat-resistance Metal Lid Connected To GND Terminal To Reduce EMI Suitable For Mobile Communications And Consumer Devices. Applications Mobile Communications And Consumer Devices, Etc. Smart Card And Wearable Devices More
SMD Tuning Fork Crystal PMX406 Features Ultra Miniature SMD Tuning Fork Crystal Resonator Plastic molded SMD tuning fork crystal of heat-resistance Metal Lid Connected To GND Terminal To Reduce EMI Suitable For Mobile Communications And Consumer Devices. Applications Mobile Communications And Consumer Devices, Etc. Smart Card And Wearable Devices More
Test Method to Measure Oscillator's Performances
Oscillation Allowance (OA) from “MICRO CRYSTAL”
Test-Methode to measure the Oscillator-Performance
-Resistor Rx is placed in series to the crystal.
-Increase Rx until oscillation stops / starts.
Oscillation Allowance (OA) from “MICRO CRYSTAL”
|
. The OA value describes the performance of the active part of the oscillator (inverter). .Rx value is increased until the oscillation starts / stops. .OA= RXstart+ESRxTAL .Safety margin: The maximal crystal ESR(Rs1,R1) must be 5 times smaller than the OA, in order to have enough safety margin for lC's production tolerances and negative influence of increasing ambient temperature on lC and crystal .ESRTYP≤OA/ 5 |
Why a Safety Margin is Needed?
Crystal ESR vs Temperature
Effective Load Capacitance
|
·CG and CD are the load capacitors of the oscillator circuit (regarded in series). They are integrated into the lC or external as SMD components. · Cstray is equal to the board layout stray(parasitic) capacitance. ·CLoadis equal to CG and CD in series + Cstray . CL of the crystal is the capacitance CLoad the crystal needs to“see”from the oscillator circuit, it is not the capacitance of the crystal itself. CLoad=CD*CG/(CD+CG))+Cstray |
Chart of△FL,Dependant on CL
Load Capacitance / pF
Load Capacitance / pF
Defining CLoad
FL: 32.768 kHz
CL:12.5 pF
Tol.:+/- 30 ppm
Always start with a known crystal!
R1 |
Fs |
C1 |
∆ FL |
C0 |
P |
㏀ |
KHz |
fF |
ppm |
pF |
㎼ |
39.684 |
32.76557 |
2.25 |
+9.9 |
0.86 |
1.037 |
|
Using a high impedance probe (0.1 pF).√ Using a standard probe (8-12 pF).Ⅹ
observation on a display over several days.√
The result represents the design offset + the crystal's tolerance (∆FL). |
Frequency vs Temperature
Conventional Tuning Fork
T: 25+/-5℃
Frequency Accuracy
Time Deviation of a 32.768 kHz Crystal
|
Deviation ppm |
Per day seconds |
Per 3days seconds |
Per month seconds |
Per year minutes |
Specified Tolerance |
+100 |
8.64 |
25.9 | 259 | 51.8 |
Specified Tolerance |
+30 |
2.59 |
7.8 | 78 | 15.6 |
Specified Tolerance |
+20 |
1.73 |
5.2 | 52 | 10.4 |
Specified Tolerance |
+10 |
0.86 |
2.6 | 26 | 5.2 |
Nominal Frequency |
0 |
0.00 | 0 | 0 | 0 |
Specified Tolerance |
-10 |
-0.86 |
-2.6 | -26 | -5.2 |
Specified Tolerance |
-20 |
-1.73 |
-5.2 | -52 | -10.4 |
Specified Tolerance |
-30 |
-2.59 |
-7.8 | -78 | -15.6 |
Specified Tolerance |
-100 |
-8.64 |
-25.9 | -259 | -51.8 |
Frequency Accuracy
Additionally to the specified tolerance,the following factors influence the total time deviation:
. The aging of the crystal as a permanent frequency shift.
. The design offset: mismatch between the crystal CL specification and the effective load capacitance of the oscillator design.
- The frequency vs temperature characteristic as a temporary frequency shift.
Example of Calculation
Crystal Tolerance |
+8.0 ppm |
crystal Aging |
-1.0 ppm |
Design Offset |
+5.8 ppm |
Temperature Drift at 35℃ |
-3.5 ppm |
Total |
+9.3 ppm |
Overtone Mode Suppression
. The overtone is the 1st harmonic mode. For Tuning Fork crystals, it's about 6.1 x higher than the fundamental mode.AT-Cut crystals have 3rd, 5th and 7th harmonics.
. Overtone suppression: the need of adding the RD resistor depends on the phase shift characteristics of the used inverter at fundamental and overtone mode frequencies.
. The resistor RD together with load capacitor CD, forms a low pass filter. Usually 220KΩ is safe.
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