MCP79521-I/SL 데이터 시트보기 (PDF) - Microchip Technology
부품명
상세내역
제조사
MCP79521-I/SL Datasheet PDF : 54 Pages
| |||
MCP795W1X/MCP795W2X
9.2 Crystal Specification and
Selection
The MCP795WXX has been designed to operate with
a standard 32.768 kHz tuning fork crystal. The on-
board oscillator has been characterized to operate with
a crystal of maximum ESR of 70K Ohms.
Crystals with a comparable specification are also
suitable for use with the MCP795WXX.
The table below is given as design guidance and a
starting point for crystal and capacitor selection.
Manufacturer
Part Number
Crystal
Capacitance
Micro Crystal
CM7V-T1A
7pF
Citizen
CM200S-32.768KDZB-UT
6pF
Please work with your crystal vendor.
CX1 Value
10pF
10pF
CX2 Value
12pF
8 pF
EQUATION 9-1:
Cload = C-C----XX----22----+------CC----XX----11-- + Cstray
The following must also be taken into consideration:
• Pin capacitance (to be included in Cx2 and Cx1)
• Stray Board Capacitance
The recommended board layout for the oscillator area
is shown in Figure 9-9. This actual board shows the
crystal and the load capacitors. In this example, C2 is
CX1, C1 is CX2 and the crystal is designated as Y1.
When calculating the effective load capacitance,
Equation 9-1 can be used.
Gerber files are available on request. Please contact
your Microchip Sales representative.
It is required that the final application should be tested
with the chosen crystal and capacitor combinations
across all operating and environmental conditions.
Please also consult with the crystal specification to
observe correct handling and reflow conditions and for
information on ideal capacitor values.
For more information please see the RTCC Best
Practices AN1365 (DS01365).
FIGURE 9-9:
BOARD LAYOUT
2011-2012 Microchip Technology Inc.
Preliminary
DS22280C-page 37
Share Link: 