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SPRS717F –OCTOBER 2011–REVISED APRIL 2013
Table 4-5. OSC1 Crystal Circuit Requirements
NAME
DESCRIPTION
MIN
TYP
MAX
UNIT
fxtal
Crystal parallel resonance
frequency
Fundamental mode oscillation only
32.768
kHz
Crystal frequency stability
and tolerance
Maximum RTC error = 10.512 minutes
per year
-20.0
-50.0
20.0
50.0
ppm
ppm
Maximum RTC error = 26.28 minutes per
year
CC1
C1 capacitance
C2 capacitance
Shunt capacitance
12.0
12.0
24.0
24.0
1.5
pF
pF
pF
kΩ
CC2
Cshunt
ESR
Crystal effective series
resistance
fxtal = 32.768 kHz, oscillator has nominal
negative resistance of 725 kΩ and worst-
case negative resistance of 250 kΩ
80
Table 4-6. OSC1 Crystal Circuit Characteristics
NAME
DESCRIPTION
MIN
TYP
0.17
0.01
MAX
UNIT
pF
Cpkg
Shunt capacitance of
package
ZCE package
ZCZ package
pF
Pxtal
The actual values of the ESR, fxtal, and CL should be used to yield a
typical crystal power dissipation value. Using the maximum values
specified for ESR, fxtal, and CL parameters yields a maximum power
dissipation value.
Pxtal = 0.5 ESR (2 π fxtal
CL VDDS_RTC)2
tsX
Start-up time
2
s
CAP_VDD_RTC (min.)
CAP_VDD_RTC
VSS_RTC
VDDS_RTC (min.)
VDDS_RTC
RTC_XTALOUT
VSS_RTC
tsX
Time
Figure 4-13. OSC1 Start-up Time
Copyright © 2011–2013, Texas Instruments Incorporated
Power and Clocking
111
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