AD9546SLASHPCBZ datasheet(80/205 Pages) AD

80 / 205 page

AD9546

Data Sheet

Rev. 0 | Page 80 of 205

REFERENCE DIVIDERS (R DIVIDERS)

Each reference input has a dedicated divider, Rx (where x

differentiates between the eight reference inputs: A, AA, B, BB,

or auxiliary REF0 to auxiliary REF3). The primary purpose of

the Rx dividers is to reduce the input reference frequency

(assuming it is greater than 200 kHz) to a value between 1 Hz

and 200 kHz to satisfy the input frequency bounds of the TDC.

The user programs Rx via the 30-bit unsigned bit fields per

Table 49. The divide ratio of Rx depends on the value, R, the user

programs in the bit fields. The user must program the bit field

with a value one less than the desired divide ratio. Thus, the Rx

dividers provide divide ratios from 1 to 1,073,741,824.

For example, for an input reference frequency of 125 MHz and

the desired Rx output frequency of 125 kHz, a divide ratio of

1000 is required. Thus, the required bit field value is 999

(0x000003E7 hexadecimal).

Table 49. Reference Divider Address Ranges

Rx Reference

REFA

0x0400 to 0x0403

REFAA

0x0420 to 0x0423

REFB

0x0440 to 0x0443

REFBB

0x0460 to 0x0463

Auxiliary REF0

0x0480 to 0x0483

Auxiliary REF1

0x04A0 to 0x04A3

Auxiliary REF2

0x04C0 to 0x04C3

Auxiliary REF3

0x04E0 to 0x04E3

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