CMX608 datasheet(11/70 Pages) CMLMICRO

11 / 70 page

RALCWI Vocoder

CMX608/CMX618/CMX638

 2014 CML Microsystems Plc

D/608_18_38/11

4.1.

PCB Layout Guidelines and Power Supply Decoupling

Figure 4 CMX618/CMX638 Power Supply and De-coupling

Component Values as per Figure 3.

Notes:

It is important to protect the analogue pins from extraneous inband noise and to minimise the impedance

between the CMX618/CMX638 and the power supply and bias de-coupling capacitors. The de-coupling

capacitors C4, C6, C7, C8, C9, C10, C12, C13 and C14 should be as close as possible to the

CMX618/CMX638. It is therefore recommended that the printed circuit board is laid out with separate

ground planes for the AVSS and (digital) VSS supplies in the area of the CMX618/CMX638, with provision

to make links between them close to the CMX618/CMX638. The use of a multi-layer printed circuit board

will facilitate the provision of ground planes on separate layers. The layout of a CMX608 printed circuit

board should make use of a single ground plane covering the whole chip area shown above.

On CMX618/CMX638, VBIAS is used as an internal reference for detecting and generating the various

analogue signals. It must be carefully decoupled, to ensure its integrity, so apart from the decoupling

capacitor shown, no other loads should be connected. If VBIAS needs to be used to set an external mid-

point reference, it must be buffered with a high input impedance buffer.

CMX608 数据表(PDF) 11 Page - CML Microcircuits