Crystal Recommendations

Table 2 shows a selection of crystals that have been tested and found suitable for various AVR microcontrollers.
Important: Since many microcontrollers share oscillator modules, only a selection of representative microcontroller products have been tested by crystal vendors. See the files distributed with the application note to see the original crystal test reports. See section Oscillator Module Overview for an overview of which microcontroller product uses which oscillator module.
Using crystal-MCU combinations from the table below will ensure good compatibility and is highly recommended for users with little or limited crystal expertise. Even though the crystal-MCU combinations are tested by highly experienced crystal oscillator experts at the various crystal vendors, we still recommend testing your design as described in Section 3, Testing Crystal Oscillation Robustness, to ensure that no issues have been introduced during layout, soldering, etc.

Table 1 shows a list of the different oscillator modules. Section 6, Oscillator Module Overview, has a list of devices where these modules are included.

Table 1. Overview of Oscillators in AVR® Devices
# Oscillator Module Description
1 X32K_2v7 2.7-5.5V oscillator used in megaAVR® devices(1)
2 X32K_1v8 1.8-5.5V oscillator used in megaAVR/tinyAVR® devices(1)
3 X32K_1v8_ULP 1.8-3.6V ultra-low power oscillator used in megaAVR/tinyAVR picoPower® devices
4 X32K_XMEGA (normal mode) 1.6-3.6V ultra-low power oscillator used in XMEGA® devices. Oscillator configured to normal mode.
5 X32K_XMEGA (low-power mode) 1.6-3.6V ultra-low power oscillator used in XMEGA devices. Oscillator configured to low-power mode.
6 X32K_XRTC32 1.6-3.6V ultra-low power RTC oscillator used in XMEGA devices with battery backup
7 X32K_1v8_5v5_ULP 1.8-5.5V ultra-low power oscillator used in tinyAVR 0-, 1- and 2-series and megaAVR 0-series devices
8 OSC_LP_v10 (normal mode) 1.8-5.5V ultra-low power oscillator used in AVR Dx series devices. Oscillator configured to normal mode.
9 OSC_LP_v10 (low-power mode) 1.8-5.5V ultra-low power oscillator used in AVR Dx series devices. Oscillator configured to low-power mode.
Note:
  1. 1.Not used with the megaAVR® 0-series or tinyAVR® 0-, 1- and 2-series.
Table 2. Recommended 32.768 kHz Crystals
Vendor Type Mount Oscillator Modules Tested and Approved (See Table 1) Frequency Tolerance [±ppm] Load Capacitance

[pF]

Equivalent Series Resistance (ESR) [kΩ]
Microcrystal CC7V-T1A SMD 1, 2, 3, 4, 5 20/100 7.0/9.0/12.5 50/70
Abracon ABS06 SMD 2 20 12.5 90
Cardinal CPFB SMD 2, 3, 4, 5 20 12.5 50
Cardinal CTF6 TH 2, 3, 4, 5 20 12.5 50
Cardinal CTF8 TH 2, 3, 4, 5 20 12.5 50
Endrich Citizen CFS206 TH 1, 2, 3, 4 20 12.5 35
Endrich Citizen CM315 SMD 1, 2, 3, 4 20 12.5 70
Epson Tyocom MC-306 SMD 1, 2, 3 20/50 12.5 50
Fox FSXLF SMD 2, 3, 4, 5 20 12.5 65
Fox FX135 SMD 2, 3, 4, 5 20 12.5 70
Fox FX122 SMD 2, 3, 4 20 12.5 90
Fox FSRLF SMD 1, 2, 3, 4, 5 20 12.5 50
NDK NX3215SA SMD 1, 2 ,3 20 12.5 80
Seiko Instruments SSP-T7-FL SMD 2, 3, 5 20 4.4/6/12.5 65
Seiko Instruments SSP-T7-F SMD 1, 2, 4, 6, 7, 8, 9 20 7/12.5 65
Seiko Instruments SC-32S SMD 1, 2, 4, 6, 7, 8, 9 20 7 70
Seiko Instruments SC-32L SMD 4 20 7 40
Seiko Instruments SC-20S SMD 1, 2, 4, 6, 7, 8, 9 20 7 70
Seiko Instruments SC-12S SMD 1, 2, 6, 7, 8, 9 20 7 90
Note:
  1. 1.Crystals may be available with multiple load capacitance and frequency tolerance options. Contact the crystal vendor for more information.