ATXMEGA256A3BU Datasheet, PDF (86/143 Pages) ATMEL Corporation – 8/16-bit Atmel XMEGA A3BUMicrocontroller

37.15.8 External 32.768kHz crystal oscillator and TOSC characteristics
Table 37-31. External 32.768kHz crystal oscillator and TOSC characteristics.
Symbol Parameter
ESR/R1
Recommended crystal equivalent
series resistance (ESR)
C_TOSC1
C_TOSC2
C_L
Parasitic capacitance TOSC1 pin
Parasitic capacitance TOSC2 pin
Parasitic capacitance load
Recommended safety factor
Condition
Crystal load capacitance 6.5pF
Crystal load capacitance 9.0pF
capacitance load matched to
crystal specification
Note:
1. See Figure 37-4 for definition.
Figure 37-4. TOSC input capacitance.
Min.
Typ.
Max. Units
60
k
35
3.0
2.9
pF
2.0
3.0
TOSC1
C_L1
C_L2
Device internal
External
TOSC2
32.768kHz crystal
The parasitic capacitance between the TOSC pins is C_L1 + C_L2 in series as seen from the crystal when oscillating without
external capacitors.
XMEGA A3BU [DATASHEET]
86
8362F–AVR–02/2013