1 GSPS Quadrature Digital Upconverter with 18-Bit I/Q Data Path and 14-Bit DAC

The AD9957 functions as a universal I/Q modulator and agile upconverter for communications systems where cost, size, power consumption, and dynamic performance are critical. The AD9957 integrates a high speed, direct digital synthesizer (DDS), a high performance, high speed, 14-bit digital-to-analog converter (DAC), clock multiplier circuitry, digital filters, and other DSP functions onto a single chip. It provides baseband upconversion for data transmission in a wired or wireless communications system.

The AD9957 is the third offering in a family of quadrature digital upconverters (QDUCs) that includes the AD9857 and AD9856. It offers performance gains in operating speed, power consumption, and spectral performance. Unlike its predecessors, it supports a 16-bit serial input mode for I/Q baseband data. The device can alternatively be programmed to operate either as a single tone, sinusoidal source or as an interpolating DAC.

The reference clock input circuitry includes a crystal oscillator, a high speed, divide-by-two input, and a low noise PLL for multiplication of the reference clock frequency.

The user interface to the control functions includes a serial port easily configured to interface to the SPORT of the Blackfin® DSP and profile pins to enable fast and easy shift keying of any signal parameter (phase, frequency, or amplitude).

Applications

* HFC data, telephony, and video modems

* Wireless base station transmissions

* Broadband communications transmissions

* Internet telephony

* 1 GSPS internal clock speed (up to 400 MHz analog output)

* Integrated 1 GSPS 14-bit DAC

* 250 MSPS input data rate

* Phase noise ≤ −125 dBc/Hz (400 MHz carrier @ 1 kHz offset)

* Excellent dynamic performance >80 dB narrow-band SFDR

* 8 programmable profiles for shift keying

* Sin(x)/(x) correction (inverse sinc filter)

* Reference clock multiplier

* Internal oscillator for a single crystal operation

* Software and hardware controlled power-down

* Integrated RAM

* Phase modulation capability

* Multichip synchronization

* Easy interface to Blackfin SPORT

* Interpolation factors from 4× to 252×

* Interpolation DAC mode

* Gain control DAC

* Internal divider allows references up to 2 GHz

* 1.8 V and 3.3 V power supplies

* 100-lead TQFPEP package