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 4 equation formating, typo edited Jun 6 '17 at 12:19 analogsystemsrf 19.6k22 gold badges99 silver badges2727 bronze badges Given $$Tjitter = Vnoise / SlewRate$$ and $$SlewRate = 2*pi*16MHz*1volt = 100 volts/uS$$, you need to identify the toleratabletolerable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SwitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz may be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT,$$Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT$$ the induced Vnoise is 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6)$$Vnoise = 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6)$$ Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126e-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before Tj = Vnoise/SLewRate$$Tj = Vnoise/SlewRate$$ = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? At 16MHz, period 66ns, the 1.3 ns jitter is 2%. Given $$Tjitter = Vnoise / SlewRate$$ and $$SlewRate = 2*pi*16MHz*1volt = 100 volts/uS$$, you need to identify the toleratable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SwitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz may be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT, the induced Vnoise is 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6) Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126e-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before Tj = Vnoise/SLewRate = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? At 16MHz, period 66ns, the 1.3 ns jitter is 2%. Given $$Tjitter = Vnoise / SlewRate$$ and $$SlewRate = 2*pi*16MHz*1volt = 100 volts/uS$$ you need to identify the tolerable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SwitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz may be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using $$Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT$$ the induced $$Vnoise = 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6)$$ Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126e-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before $$Tj = Vnoise/SlewRate$$ = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? At 16MHz, period 66ns, the 1.3 ns jitter is 2%. 3 typos, mathjax edited Jun 3 '17 at 6:41 analogsystemsrf 19.6k22 gold badges99 silver badges2727 bronze badges Given Tjitter = Vnoise / SlewRate,$$Tjitter = Vnoise / SlewRate$$ and SlewRate is 2*pi*16MHz*1volt = 100 volts/uS$$SlewRate = 2*pi*16MHz*1volt = 100 volts/uS$$, you need to identify the toleratable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SWitchingRegSwitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz willmay be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT, the induced Vnoise is 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6) Vnoise Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126ee126e-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before Tj = Vnoise/SLewRate = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? At 16MHz, period 66ns, the 1.3 ns jitter is 2%. Given Tjitter = Vnoise / SlewRate, and SlewRate is 2*pi*16MHz*1volt = 100 volts/uS, you need to identify the toleratable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SWitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz will be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT, the induced Vnoise is 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6) Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126ee-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before Tj = Vnoise/SLewRate = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? At 16MHz, period 66ns, the 1.3 ns jitter is 2%. Given $$Tjitter = Vnoise / SlewRate$$ and $$SlewRate = 2*pi*16MHz*1volt = 100 volts/uS$$, you need to identify the toleratable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SwitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz may be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT, the induced Vnoise is 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6) Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126e-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before Tj = Vnoise/SLewRate = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? At 16MHz, period 66ns, the 1.3 ns jitter is 2%. 2 added 51 characters in body edited Jun 2 '17 at 6:36 analogsystemsrf 19.6k22 gold badges99 silver badges2727 bronze badges Given Tjitter = Vnoise / SlewRate, and SlewRate is 2*pi*16MHz*1volt = 100 volts/uS, you need to identify the toleratable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SWitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz will be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT, the induced Vnoise is 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6) Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126ee-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before Tj = Vnoise/SLewRate = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? At 16MHz, period 66ns, the 1.3 ns jitter is 2%. Given Tjitter = Vnoise / SlewRate, and SlewRate is 2*pi*16MHz*1volt = 100 volts/uS, you need to identify the toleratable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SWitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz will be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT, the induced Vnoise is 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6) Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126ee-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before Tj = Vnoise/SLewRate = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? Given Tjitter = Vnoise / SlewRate, and SlewRate is 2*pi*16MHz*1volt = 100 volts/uS, you need to identify the toleratable Tjitter and be realistic about the dB/dT (change in magnetic interference near the XTAL/Cpi1/Cpi2/ MCUGND/MCUVDD/XTALin/XTALout). Suppose your PCB has SWitchingReg with 100MHz discontinuous ringing of amplitude 0.1 amps, 1cm from the XTAL/Cpi. 100MHz will be seriously attenuated by SkinDepth, depending on direction of arrival at 1cm by 1cm XTAL/Xpi area. Using Vinduce = MU0 * MUr * Area / (2 *pi * distance) * dI/dT, the induced Vnoise is 2e-7 * 1cm * 1cm / 1cm * (0.1 * 628e+6) Vnoise is 2e-7 * 0.01 * 63e+6 = 126 e-7-2+6 = 126ee-3 = 0.126 volts. The resultant XTAL Jitter, out of the onchip sin-to-square circuit is as before Tj = Vnoise/SLewRate = 0.126 volts/10^+8volt/sec = 10 nanoseconds * 0.126 = 1.26 nanoseconds. Can your system tolerate 1.26 nanoseconds of jitter, caused by the nearby SwitchReg upsetting the XTAL voltages? At 16MHz, period 66ns, the 1.3 ns jitter is 2%. 1 answered Jun 2 '17 at 3:55 analogsystemsrf 19.6k22 gold badges99 silver badges2727 bronze badges