Post Go back to editing

ADV7282A 28.636MHz Quartz Specification

Category: Datasheet/Specs
Product Number: ADV7282A

How critical is the ESR value for the 28.63636MHz for this product, I am having a few issues with suppliers.

I have various suppliers with different ESR Max values, 35ohms another with 40 ohms and another with 50ohms on their datasheets for this 28.63636MHz quartz in this package size.

How will this affect or not affect my setup.

Also I would like clarification on the total frequency tolerance required for this product, on page 6 of the datasheet is states 

,Frequency Stability ±50 ppm

But then in the table on page 16 it states,

Frequency Calibration (at 25°C) ±20 ppm
Frequency Temperature StabilityTolerance ±50 ppm

Aging per Year ±3 ppm

So does that mean that to get the total tolerance I have 20ppm + 50ppm + aging?

Parents
  • PDF

    The original oscillator design was based on a 30 Ohm crystal.  This application note shows that you can change the load capacitors to work with other crystal impedances.  The goal is to get the crystal to spin at the right frequency at room temp.

    The 50+-ppm is for total tolerance over temperature.  What is important is the initial frequency at 25C.  For load caps use COG(NPO) caps.  They have the best temperature stability.

Reply
  • PDF

    The original oscillator design was based on a 30 Ohm crystal.  This application note shows that you can change the load capacitors to work with other crystal impedances.  The goal is to get the crystal to spin at the right frequency at room temp.

    The 50+-ppm is for total tolerance over temperature.  What is important is the initial frequency at 25C.  For load caps use COG(NPO) caps.  They have the best temperature stability.

Children
  • Thank you for your quick response, I just need to confirm clearly the official specification for this 28.636MHz quartz.

    You write total tolerance over temperature of 50+/-ppm, but how many ppm is the initial tolerance..

    What I need is the breakdown for the total ppm.

    Initial tolerance = ?

    Tolerance over temperature = ?

    Aging = ?

    With this I get the total tolerance of everything added together at the end to give to the supplier.

  • The crystal used to design the original oscillator is attached.  The basic design has changed very little over the years.  See the attached pdf.  This part is hard to get now but readily available from other vendors.

    PDF

    Initial tolerance += 30 ppm

    Over temp +- 50 ppm

    ageing +- 3ppm/year.

    Depending on the circuit this crystal is used to generate the color burst frequency,  Other circuits use it for timing measurement.