XE8000EV108 Semtech, XE8000EV108 Datasheet - Page 46

• Manufacturer Part Number: XE8000EV108
• Description: EVAL BOARD FOR XE8806/XE8807
• Manufacturer: Semtech
• Type: MCUr

Specifications of XE8000EV108

• Contents: Fully Assembled Evaluation Board
• For Use With/related Products: XE88LC06AMI026
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

7.7
7.7.1
The Xtal operates with an external crystal of 32’768 Hz. During Xtal oscillator start-up, the first 32768 cycles are
masked. The two bits EnableXtal and ColdXtal in register RegSysClock control the oscillator.
At power-on reset, a pad NRESET pulse or during sleep mode, EnableXtal is reset and ColdXtal is set (Xtal
oscillator is not selected at start-up). The user can start Xtal oscillator by setting EnableXtal. When the Xtal
oscillator starts, bit ColdXtal is reset after 32768 cycles. Before ColdXtal is reset by the system, the Xtal
frequency precision is not guaranteed. The Xtal oscillator can be stopped by the user by resetting bit EnableXtal.
When the user enters into sleep mode, the Xtal is stopped.
7.7.2
The crystal oscillator has been designed for a crystal with the specifications given in Table 7-9. The oscillator
precision can only be guaranteed for this crystal.
Table 7-9. Crystal specifications.
For safe operation, low power consumption and to meet the specified precision, careful board layout is required:
Table 7-10. Board layout specifications.
© Semtech 2006
Symbol
Fs
CL
Rm
Cm
C0
Rmp
Q
Symbol
Rh_xin
Rh_xout
Rh_xin_xout
Cp_xin
Cp_xout
Cp_xin_xout
Xtal oscillator
Keep lines XIN and XOUT short and insert a VSS line in between them.
Connect the crystal package to VSS.
No noisy or digital lines near XIN or XOUT.
Insert guards where needed.
Respect the board specifications of Table 7-10.
Xtal configuration
Xtal oscillator specifications
Description
Resonance frequency
CL for nominal
frequency
Motional resistance
Motional capacitance
Shunt capacitance
Motional resistance of
6
Quality factor
th
overtone (parasitic)
Description
Resistance XIN-VSS
Resistance XOUT-
VSS
Resistance XIN-
XOUT
Capacitance XIN-
VSS
Capacitance XOUT-
VSS
Capacitance XIN-
XOUT
Min
Min
30k
1.8
0.7
0.5
0.5
0.2
10
10
50
4
32768
Typ
Typ
50k
8.2
2.5
1.1
40
7-7
8
400k
Max
Max
100
3.2
2.0
3.0
3.0
1.0
15
Unit
Hz
pF
kΩ
fF
pF
kΩ
-
Unit
MΩ
MΩ
MΩ
pF
pF
pF
XE8806A/XE8807A
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