For customers designing Mircochip (Former Atmel)

Contents

We are pleased to introduce you to our crystal unit.
Crystal Recommendations for Mircochip (Former Atmel) Corporation "AVR RF chips".

Items to Confirm (designing of oscillation circuit)

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

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

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.

Epson Crystal Product Lineup

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

Clock solution recommendations for Mircochip (Former Atmel) AVR RF chips

Worldwide ATmega
256RFR2
ATmega
128RFA1		 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, CL=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 Mircochip (Former Atmel) AVR RF chips manual for designing.
*ZigBee is a registered trademark of Koninklijke Philips Electronics N.V.

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

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
WxDxH
[mm]
Cg
[pF]		 Cd
[pF]
ATmega256RFR2 FA-20H 16M 9.0 10 Q24FA20H00352** 12 12 2.5 x 2.0 x 0.55
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.