CMX7861 FirmCODEC® Programmable Baseband Interface
CMX7861
5
External Components
5.1 Xtal Interface
C1
C2
XTAL/CLK
XTALN
50
49
X1
DVSS
X1
For frequency range see
8.1.2 Operating Limits
22pF typical
C1
C2
22pF typical
Figure 3 Recommended External Components - Xtal Interface
Notes:
The clock circuit can operate with either a Xtal or external clock generator. If using an external clock
generator it should be connected to the XTAL/CLK pin and the Xtal and other components are not
required. For external clock generator frequency range see 8.1.2 Operating Limits. When using an
external clock generator the Xtal oscillator circuit may be disabled to save power, see 9.2.3 Program
Block 1 – Clock Control for details. Also refer to section 7.1 Xtal Frequency.
The tracks between the Xtal and the device pins should be as short as possible to achieve maximum
stability and best start up performance. It is also important to achieve a low impedance connection
between the Xtal capacitors and the ground plane.
The DVSS to the Xtal oscillator capacitors C1 and C2 should be of low impedance and preferably be part
of the DVSS ground plane to ensure reliable start up. For correct values of capacitors C1 and C2 refer to
the documentation of the Xtal used.
5.2 C-BUS Interface
DVDD
R2
IRQN
57
CSN
56
CDATA
55
RDATA
54
SCLK
53
R2
Figure 4 Recommended External Components - C-BUS Interface
10k - 100k
Note:
If the IRQN line is connected to other compatible pull-down devices only one pull-up resistor is required
on the IRQN node.
2012 CML Microsystems Plc
Page 11
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