AD9546SLASHPCBZ datasheet(162/205 Pages) AD

162 / 205 page

AD9546

Data Sheet

Rev. 0 | Page 162 of 205

AUXILIARY NCOS

AUXILIARY NCO OVERVIEW

The AD9546 has two auxiliary NCOs as shown in Figure 111. The

NCOs generate time stamps and/or physical output signals based

on a very precise programmable frequency specified by the user.

The auxiliary NCOs also provide a time scale to the UTSPs (see the

User Time Stamp Processor (UTSP) section). The NCOs have

frequency tuning resolution of 2−40 Hz, or approximately 1 pHz.

AUXILIARY NCO FREQUENCY

The user programs the output frequency of the auxiliary NCOs

(fAUX) by assigning a center frequency and an offset frequency.

By default, the offset frequency value is zero, which means the

default output frequency is the center frequency. Figure 110

details the relationship between the center frequency (56 bits) and

offset frequency (32 bits) register values.

The auxiliary NCO is effectively a direct digital synthesizer (DDS)

with a phase accumulator. The DDS accumulates a given phase

value, θ, at a prescribed rate, fACCUM.

fACCUM = fS/96

where fS is the system clock frequency (see the System Clock PLL

section). The auxiliary NCO calculates θ such that the

accumulator rolls over with a period of precisely 1/fAUX.

Auxiliary NCO Center Frequency

Center frequency assignment is via Bits[55:0] (unsigned) of

Bits[55:0] carry units of 2−40 Hz. Thus, the center frequency

value of Bits[55:0] relates to the center frequency, fCENTER, as

fCENTER = Center Frequency Value × 2−40

For example, given a desired center frequency of 10 kHz, find the

required 56-bit register value.

Center Frequency Value = fCENTER × 240

= 104 × 240

= 10,995,116,277,760,000

= 0x 27 1000 0000 0000 (hexadecimal)

The center frequency upper limit is 65,536 Hz (256 × 2−40 Hz).

CENTER

OFFSET

2–24 Hz

2–40 Hz

...

FRACTIONAL Hz

INTEGER Hz

OUTPUT = CENTER + OFFSET

56-BIT CENTER FREQUENCY

32-BIT OFFSET FREQUENCY

DECIMAL

POINT

Figure 110. Auxiliary NCO Frequency Tuning

AD9546/PCBZ データシート(PDF) 162 Page - Analog Devices

AD9546/PCBZ データシート(HTML) 162 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

データシートダウンロード