16.257 MHz — ±10ppm stability in the ECX-32 surface-mount family
The ECS-162.57-20-33-CKM-TR: For a communication MCU generating a UART baud rate at this frequency, ±10ppm means the accumulated timing error stays below the baud-rate tolerance threshold over the expected frame length. The ESR is 80 Ω; this value governs the drive level the oscillator IC must source to start the part — an oscillator with insufficient negative-resistance margin relative to 80 Ω ESR will exhibit intermittent cold-start failures that are easy to misdiagnose as a bad crystal rather than a matching problem.
Load capacitance, package footprint, and the matching question
The 20pF load capacitance specification means the oscillator circuit must present 20 pF to the crystal terminals for the part to oscillate at its nominal 16.257 MHz. The two external load capacitors that most reference designs add to ground — one on each crystal pin — combine with the oscillator input capacitance and PCB parasitic capacitance to form the total load. If the actual total is lower than 20 pF the crystal runs sharp; if higher it runs flat, and either case degrades the accuracy budget.
Listed as Active by ECS Inc. The 16.257 MHz frequency is a specific timing value — confirm the exact frequency tolerance the downstream oscillator requires before committing to the ±10ppm figure on this part, since tighter tolerance crystals in the same ECX-32 package are available if the application demands it.