AD9957SLASHPCBZ datasheet(21/62 Pages) AD

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AD9957

Data Sheet

Rev. E | Page 20 of 61

SINGLE TONE MODE

A block diagram of the AD9957 operating in single tone mode

is shown in Figure 29; grayed items are inactive. In this mode,

both I and Q data paths are disabled from the 18-bit parallel

data port up to, and including, the modulator. The internal

DDS core produces a single frequency signal based on the

programmed tuning word. The user may select either the

cosine or sine output of the DDS. The sinusoid at the DDS

output can be scaled using a 14-bit amplitude scale factor (ASF)

and optionally routed through the inverse sinc filter.

Single tone mode offers the output shift keying (OSK) function.

It provides the ability to ramp the amplitude scale factor between

zero and an arbitrary preset value over a programmable time

interval.

PDCLK

I/Q IN

DAC_RSET

IOUT

TxENABLE

FTW

DAC GAIN

CLOCK

SYSCLK

PLL

÷2

REF_CLK

REFCLK_OUT

XTAL_SEL

PARALLEL DATA

TIMING AND CONTROL

AD9957

cos (ωt+θ)

sin (ωt+θ)

DDS

AUX

DAC

8-BIT

POWER

DOWN

CONTROL

RAM

SERIAL I/O

PORT

PROGRAMMING

REGISTERS

I Q

IS QS

OSK

INTERNAL CLOCK TIMING AND CONTROL

DAC

14-BIT

OUTPUT

SCALE

FACTOR

Figure 29. Single Tone Mode

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