For customers designing Atmel Corporation

We are pleased to introduce you to our crystal unit

Crystal Recommendations for Atmel Corporation "AVR RF chips".

Clock solution recommendations for Atmel Corporation AVR RF chips

In realizing low power consumption RF designs, the following factors should be taken into consideration.

  1. Oscillation start-up time
  2. Frequency tuning
  3. Lower BER(Bit Error Rate) over operating temperature
No. Oscillation Circuit Factor 2.4 GHz
< AT crystal unit spec.>
1 Quick oscillation start-up time
*High oscillation allowance
*Boost inverter
*Lower ESR(R1)
*High drive level
2 Easy frequency control
*inner frequency tuning capacitor
*proper frequency sensitivity
*low parameters' variation
3 Lower BER
*temperature compensation
*High frequency stability

IC Inside

MHz Crystal equivalent circuit MHz Crystal equivalent circuit
Rapid Oscillation start-up time
→ Lower ESR (R1) , Higher C1
→ Higher drive level
Rapid Oscillation start-up time
Suitable Frequency Tuning
→ Lower parameters variation(C0,C1,L1,ESR)
Suitable Frequency Tuning
Suitable Frequency Tuning
→ Proper Sensitivity (CL,C0)
Suitable Frequency Tuning
Higher Frequency Stability
→ Stable fSTA
Higher Frequency Stability
QMEMS Technology

Clock solution recommendations for Atmel Corporation AVR RF chips

Worldwide ATmega256RFR2
ATmega128RFA1
AT86RF233
AT86RF231
AT86RF212B
AT86RF212
US Europe Japan Asia
ZigBee
IEEE802.15.4
2400 to 2483.5 MHz 700/800/900 MHz
Recommendable
Clock Devices
FA-20H
16MHz,9pF

Notes: Above recommendations are based on actual evaluation results and intended to support users in picking the right components. As the actual board layout and choice of external components influences the best suitable crystal load capacitance, We does not assume any responsibility and grant warranty for above recommendations. Users design must be verified and decided by own and individual evaluation.
Please refer to Atmel Corporation AVR RF chips manual for designing.

*ZigBee is a registered trademark of Koninklijke Philips Electronics N.V.

Items to Confirm (designing of oscillation circuit)

Please note: to design oscillation circuit, you need to confirm the electronic characteristics as follows:

Oscillation allowance and Negative resistance (-R):
You need to confirm oscillation capability.
We recommend the condition: (-R) / ESR > 5
* -R: Negative resistance, ESR: Equivalent Series Resistance
Please refer to our web site:
http://www5.epsondevice.com/en/information/precaution/design.html
Support information > Precautions in Designing oscillation circuits > 2. Allowance for oscillation

Drive Level:
You need to confirm if oscillation is stable, and if the drive level is within the specification.
Please refer to our web site:
http://www5.epsondevice.com/en/information/precaution/design.html
Support information > Precautions in Designing oscillation circuits > 1. Drive level

Load Capacitance:
Load capacitance affects frequency stability, oscillation allowance, negative resistance, and start-up time of oscillation.
In addition the load capacitance is determinative factor of crystal unit's load capacitance (CL value) directly.
Please refer to our web site:
http://www5.epsondevice.com/en/information/precaution/design.html
Support information > Precautions in Designing oscillation circuits > 3. Load capacitance

* frequency stability: frequency deviation out of circuit conditions.

Selection Guidance for crystal unit

When Customer selects crystal unit, load capacitance (CL value) is an important factor of the selection.
For instance, crystal with small CL(7.0 pF) makes larger oscillation allowance, smaller current consumption and worse frequency stability, like below table.
Oppositely, crystal with large CL(12.5 pF) makes smaller oscillation allowance, larger current consumption and better frequency stability.
Please select it in consideration of these characteristics.

Selection Guidance for crystal unit

Epson Crystal Product Lineup

Product Size [mm] Applications Images
FA-20H
2.5×2.0×0.55t -Mobile phone,Bluetooth,W-LAN
-ISM band,Clock for MPU
FA238.A233V

Oscillation Circuit and Selection Guidance of Crystal Unit for AVR RF chips

AVR RF

Pin number of XTAL1/XTAL2

XTAL1 XTAL2
ATmega256RFR2 57 56
ATmega128RFA1 57 56
AT86RF23x, 212/212B 26 25

Internal trimming capacitors of AVR RF chips (Default)

Ctrim (XTAL_TRIM) 0 pF
IC
name
product
name
Freq.
[Hz]
CL
*1
[pF]
f_tol
*2
[ppm]
Product
Code*3
External parts *4 Package
size[mm]
WxDxH
Cg
[pF]
Cd
[pF]
ATmega256RFR2 FA-20H 16M 9.0 10 Q24FA20H00352** 12 12 2.5x2.0x0.55
ATmega128RFA1
AT86RF233 20 Q24FA20H00053** 12 12
AT86RF231
AT86RF212B
AT86RF212

Notes:*

  1. Load capacitance.
  2. Frequency tolerance (standard)
  3. Two digits of the product code is packing specification, please refer here for the detail.
  4. Above recommendations are based on actual evaluation results and intended to support users in picking the right components. And the results are only according to the sample set that received from our customers, so it is not including the dispersion trend of IC and the external parts.
    As the actual board layout and choice of external components influences the best suitable crystal load capacitance, We do not assume any responsibility and grant warranty for above recommendations. Users design must be verified and decided by own and individual evaluation.
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