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| PT7C43390 Datasheet, PDF (7/38 Pages) Pericom Semiconductor Corporation – Real-time Clock Module | |||
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Recommended Layout for Crystal (for PT7C43390)
PT7C43390/43390C
Real-time Clock Module
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Built-in Capacitors Specifications and Recommended External Capacitors
Parameter
Symbol
Typ.
Unit
Build in capacitors
XIN to GND
CG
XOUT to GND
CD
Recommended External capacitors for crystal
XIN to GND
C1
CL=12.5pF
XOUT to GND
C2
5
pF
5
pF
18
pF
18
pF
Recommended External capacitors for crystal
XIN to GND
C1
CL=6pF
XOUT to GND
C2
7
pF
7
pF
Note: The frequency of crystal can be optimized by external capacitor C1 and C2, for frequency=32.768 kHz, C1 and C2 should
meet the equation as below: Cpar + [(C1+CG)*(C2+CD)]/ [(C1+CG) + (C2+CD)] =CL
Cpar is all parasitical capacitor between X1 and X2.
CL is crystalâs load capacitance.
Crystal Specifications
Parameter
Nominal frequency
Serial resistance
Load capacitance
Symbol
fO
ESR
CL
Min.
-
-
-
Typ.
32.768
-
6/12.5
Max.
Unit
-
kHz
70
kΩ
-
pF
2015-12-0001
PT0280-8 12/11/15
7
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