CMX860 データシートの表示（PDF） - CML Microsystems Plc

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CMX860

Telephone Signalling Transceiver

CML Microsystems Plc 

Telephone Signalling Transceiver / Least Cost Router

1.4 External Components

CMX860

C1, C2

R1

X1

22pF

100kΩ

11.0592MHz

or 12.288MHz

C3, C4, C6

C5, C7

L1, L2

100nF

10uF

100nH

(optional)

Resistors ±5%, capacitors and inductors ±20% unless otherwise stated.

Figure 2a Recommended External Components for a Typical Application

This device is capable of detecting and decoding small amplitude signals. To achieve this DVDD, AVDD

and VBIAS should be decoupled and the receive path protected from extraneous in-band signals. It is

recommended that the printed circuit board is laid out with both AVSS and DVSS ground planes in the

CMX860 area, as shown in Figure 2b, with provision to make a link between them close to the CMX860.

To provide a low impedance connection to ground, the decoupling capacitors (C3 – C7) must be mounted

as close to the CMX860 as possible and connected directly to their respective ground plane. This will be

achieved more easily by using surface mounted capacitors.

VBIAS is used as an internal reference for detecting and generating the various analogue signals. It must

be carefully decoupled, to ensure its integrity. Apart from the decoupling capacitor shown (C3), no other

loads are allowed. If VBIAS needs to be used to set external analogue levels, it must be buffered with a

high input impedance buffer.

The DVSS connections to the Xtal oscillator capacitors C1 and C2 should also be of low impedance and

preferably be part of the DVSS ground plane to ensure reliable start up of the oscillator.

© 2002 Consumer Microcircuits Limited

8

D/860/5

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