BC41B143A-ds-003Pc CSR, BC41B143A-ds-003Pc Datasheet - Page 50

• Manufacturer Part Number: BC41B143A-ds-003Pc
• Description: Blue Core ROM Plug-n-Go
• Manufacturer: CSR

The BlueCore4-ROM Plug-n-Go driver circuit is a transconductance amplifier. A voltage at XTAL_IN generates a
current at XTAL_OUT. The value of transconductance is variable and may be set for optimum performance.
10.3.2 Load Capacitance
For resonance at the correct frequency the crystal should be loaded with its specified load capacitance, which is
defined for the crystal. This is the total capacitance across the crystal viewed from its terminals. BlueCore4-ROM
Plug-n-Go provides some of this load with the capacitors C
capacitors labelled C
the signal swing, hence, slew rate at XTAL_IN (to which all on-chip clocks are referred). Crystal load capacitance, C
is calculated with Equation 10.1:
Where:
Note:
BC41B143A-ds-003Pc
Frequency
Initial Tolerance
Pullability
C
C
C
trim
int
int
= 1.5pF
does not include the crystal internal self capacitance; it is the driver self capacitance.
= 3.4pF nominal (mid-range setting)
t1
and C
t2
. C
t1
8MHz
Min
should be three times the value of C
-
-
© Cambridge Silicon Radio Limited 2005
Equation 10.1: Load Capacitance
Table 10.3: Crystal Specification
C
I
=
Advance Information
C
int
+
C
trim
2
trim
+
C
and C
C
±20ppm/pF
1 t
±25ppm
1 t
16MHz
+
•
C
Typ
C
2 t
int
2 t
. The remainder should be from the external
t2
for best noise performance. This maximises
Device Terminal Descriptions
32MHz
Max
-
-
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