AM7968-125JC datasheet(102/127 Pages) AMD

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AMD

TAXIchip Integrated Circuits Technical Manual

TAXI Technical Information Publication #89-04

Subject: TAXI PLL Lock-Up During Power-On!

Question:

Is there a recommended power-on sequence for the TAXIchips to prevent PLL lock-up?

Answer:

Early versions of the -70 TAXIchips did have some sensitivities associated with hot-

plug-in lock-up, fast VCC rise time, and/or power supply sequencing during power-on

causing occasional PLL lock-up. These potential problems were addressed in the -125

TAXIchips with an improved circuit design. The -125 TAXIchips do not exhibit any

known power-on problems, but a PLL Reset function is available on a package pin and

may be used to restart the PLL if problems occur.

Use of the external PLL Reset pin should not be necessary with the -125 TAXIchips, but

there may be specific situations where its use may be helpful with the TAXI Receiver.

There are possible situations where large amounts of noise may occur on the Receiver

serial data inputs. Under these conditions the Rx-PLL may attempt to track the noise to

an indeterminate frequency. This deviation in frequency may adversely affect data

recovery when a good data stream reappears. System requirements may also place a

restriction on the allowed clock frequency deviation. Use of the PLL Reset function on

the Receiver may assist in the containment of some of these effects.

All VCCs may be powered-on simultaneously with a common supply. It is only recom-

mended that the TAXI GND pins be connected to a common Ground and the VCC pins

be separately filtered and decoupled to that Ground. Variations in power-on times due to

separate VCC filtering and decoupling are not a problem. Use of a common VCC supply is

sufficient as long as noise filtering of the supply at the TAXI VCC pins is adequate,

therefore use of separate power supplies for the VCCs is usually not necessary.

Refer to Section 6.1, for more information concerning power supply layout and decoupling. Further

information is also available in TAXI TIP #89-02,

TAXI Receiver RESET Pin Function.

AM7968-125JC Datenblatt(PDF) 102 Page - Advanced Micro Devices