33.10 Oscillators and Clocks

Operating conditions:
  • VDD = 3V, unless otherwise specified
  • Oscillator frequencies above speed specification must be divided, so the CPU clock is always within specification
Table 33-12. 20 MHz Internal Oscillator (OSC20M) Characteristics
SymbolDescriptionConditionMin.Typ.Max.Unit
fOSC20MFactory calibration frequencyFREQSEL = 0x01TA = 25°C, 3.0V-16-MHz
FREQSEL = 0x02-20-
fCALFrequency calibration rangeOSC20M FREQSEL = 0x0114.5-17.5MHz
OSC20M FREQSEL = 0x0218.5-21.5MHz
ETOTALTotal error with 16 MHz and 20 MHz frequency selectionFrom target frequency TA = 25°C, 3.0V-1.5-1.5%
TA = [0, 70]°C, VDD = [1.8, 3.6]V-2.0(1)-2.0(1)%
Full operation range-3.5-3.5
ΔfOSC20MCalibration step size -0.75-%
DOSC20MDuty cycle -50-%
tstartupStart-up timeWithin 2% accuracy-12-µs
Note:
  1. These values are based on characterization and are not covered by production test limits.
Table 33-13. 32.768 kHz Internal Oscillator (OSCULP32K) Characteristics
SymbolDescriptionConditionMin.Typ.Max.Unit
fOSCULP32KFactory calibration frequency-32.768-kHz
Factory calibration accuracyTA = 25°C, 3.0V-3-3%
ETOTALTotal error from target frequencyTA = [0, 70]°C, VDD = [1.8, 3.6]V-10(1)-+10(1)%
Full operation range-20-+20
DOSCULP32KDuty cycle-50-%
tstartupStart-up time-250-µs
Note:
  1. These values are based on characterization and are not covered by production test limits.
Table 33-14. 32.768 kHz External Crystal Oscillator (XOSC32K) Characteristics
SymbolDescriptionConditionMin.Typ.Max.Unit
foutFrequency -32.768-kHz
tstartupStart-up timeCL = 7.5 pF-300-ms
CLCrystal load capacitance 7.5(1)-12.5(1)pF
ESREquivalent Series Resistance - Safety Factor=3CL = 7.5 pF--80(1)kΩ
CL = 12.5 pF--40(1)
Note:
  1. This parameter is for design guidance only. Not production tested.
Figure 33-4. External Clock Waveform Characteristics
Table 33-15. External Clock Characteristics
SymbolDescriptionConditionVDD=[1.8, 5.5]VVDD=[2.7, 5.5]VVDD=[4.5, 5.5]VUnit
Min.Max.Min.Max.Min.Max.
fCLCLFrequency 05.00.010.00.020.0MHz
tCLCLClock Period 200-100-50-ns
tCHCX(1)High Time 80-40-20-ns
tCLCX(1)Low Time 80-40-20-ns
tCLCH(1)Rise Time (for maximum frequency) -40-20-10ns
tCHCL(1)Fall Time (for maximum frequency) -40-20-10ns
ΔtCLCL(1)Change in period from one clock cycle to the next -20-20-20%
Note:
  1. This parameter is for design guidance only. Not production tested.