Pierce Analyzer System (PAS) - Advanced Board Characterization Service EXPEDITED-PAS-SVC STANDARD-PAS-SVC Introduction The majority of electronic designs have some form of timing associated with them. Depending on the frequency accuracy requirements, some employ oscillators while others use off-the-shelf crystals in conjunction with the built-in oscillator circuit embedded in most controllers and processors. Most if not all embedded solutions use the Pierce Oscillator configuration, integrated as part of the SOC (system on chip). The obvious advantages include cost, size and power compared to a stand-alone oscillator while the key limitation is the proper matching of the quartz crystal with the on-board Pierce Oscillator. Figure (1) outlines the oscillator block and the key components that influence the overall performance of the timing loop. Effective Loaded Capacitance, as seen by the Crystal = CL CL = ((Cin+C1) x (C2+Cout)) / (Cin+C1+C2+Cout) + Board Strays For example Let C1 = C2 = 27 pF Cin = 5.0 pF & Cout = 10.0 pF and Board Strays = 0.50 pF then CL = ((27+5) x (27+10)) / (5+27+27+10) + 0.50 = 17.65 pF Therefore specifying a crystal with 18.0 pF plating load capacitance would be the closest match for frequency accuracy. Besides the frequency accuracy issue, while accounting for Quartz Crystals set tolerance the reactive impedance (Xc) of the loop capacitors, in combination with the Inverter Amplifiers transconductance (gm), the current limiting resistor Rs and the presence or absence of the AGC or ALC circuit as part of the oscillator loop determines the boundary condition of the design. This boundary condition, commonly referred to as the Safety Factor (SF), is an important parameter to ensure that the product design has sufficient margin to accommodate part-to-part and lot-to-lot variations as well as eliminating product performance uncertainty in production volume. 5101 Hidden Creek Ln Spicewood TX 78669 ABRACON IS Phone: 512-371-6159 Fax: 512-351-8858 REVISED: 08-7-19 ISO9001-2015 LLC For terms and conditions of sales, please visit: CERTIFIED www.abracon.comPierce Analyzer System (PAS) - Advanced Board Characterization Service EXPEDITED-PAS-SVC STANDARD-PAS-SVC Historically, design engineers have optimized their circuit performance via trial & error, at the expense of significant investment in time. Further, to properly determine the oscillator loop dynamics, there is no other choice but to break the oscillator loop and make key measurements using specialized equipment such as a Current Probe. Lastly, these measurements become increasingly sensitive if the timing loop is driven by a Tuning Fork (32.768kHz) crystal. These crystals are extremely sensitive to loading effects and to accurately determine the in-circuit behavior of these components, extreme care and accuracy is essential. For instance, Automotive, Medical and Consumer Electronics solutions typically utilize Tuning Fork Crystals for their Real-Time-Clocking (RTC) needs. If the selected SOC has inadequate gain margin, there is a high probability that some percentage of these Crystals will not properly start under adverse conditions, such as low operating temperature. Another example would be a Zigbee based design which has a hard boundary condition of 40 ppm relative to the carrier, for proper operation. If the oscillator loop is not optimized, most of the 40 ppm can be consumed by tolerance alone thereby causing significant fall out in the field. In summary, a typical product launch requires significant investment of capital and design resources. Making a very modest investment in characterizing the timing loop is a must have to protect this investment, as well as mitigate risk of field failures or warranty re-calls. Solution To overcome these barriers and provide an accurate assessment of the oscillator loop dynamics Abracons Advanced Engineering Team has developed a Proprietary Pierce Analyzer System (PAS) which is designed to analyze both the stand alone crystal, as well as the performance of that particular crystal in customers circuit. 5101 Hidden Creek Ln Spicewood TX 78669 ABRACON IS Phone: 512-371-6159 Fax: 512-351-8858 REVISED: 08-7-19 ISO9001-2015 LLC For terms and conditions of sales, please visit: CERTIFIED www.abracon.com