Appendix C: Application Information

CDCE421A

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CDCE421 User Information

The CDCE421A includes several device enhancements to the CDCE421.

• Device Startup

The CDCE421A includes an improved device startup circuit that enables the CDCE421A to be used in

stand-alone applications (for example, configurations in which the device is not connected to a host system).

This design operates over various power-supply ramp time scenarios. For proper operation of the startup

circuit, certain register bits must be programmed as specified in Table 15.

Table 15. CDCE421 vs. CDCE421A Register Settings

CDCE421A

DATA SHEET

REGISTER LOCATION

CDCE421

CDCE421A

REFERENCE

TITEST1 (must always

Word 0, Bit 10

Loop filter bias select

Table 7

be written '1')

TITEST2 (must always

Word 3, Bit 10

Not used

Table 10

be written '0')

space

• LVDS Output Buffer

The CDCE421A incorporates an improved LVDS output buffer. Therefore, the electrical characteristics of the

LVDS output buffer on the CDCE421A are different from those of the CDCE421. Refer to the Electrical

Characteristics table for the details of the CDCE421A LVDS output buffer.

• Product Revision Identification

For the product revision identifier bits (bits [2:0]), the value presented by the CDCE421A is '000'. See Table 6

for more details.

Copyright © 2009, Texas Instruments Incorporated

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