Analog's AD9122 DAC supports high data rates

An Analog Devices product story
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Edited by the Electronicstalk editorial team Sep 29, 2009

Analog Devices has launched the AD9122, a dual-channel, 1.2GSPS (giga-sample-per-second), 16-bit digital-to-analogue converter (DAC).

The AD9122 DAC is designed to support the high data rates and complex modulation schemes required for advanced multi-carrier wireless and broadband communications equipment.

Analog Devices said the AD9122 DAC features an on-chip 32-bit numerically controlled oscillator (NCO) that allows flexible placement of the intermediate frequency (IF) to help optimise system performance.

It added that the AD9122 satisfies requirements for multi-standard cellular base stations and other applications that use digital pre-distortion (DPD) techniques demanding broad signal widths.

The wireless communications standards that the AD9122 supports include GSM, WCDMA, TD-SCDMA, CDMA2000, WiMAX, and LTE.

The combination of the AD9122 dual DAC and ADI's ADL5375 quadrature modulator and AD9516 14-output clock generator meets or exceeds six multi-carrier GSM specifications for intermodulation distortion and signal-to-noise ratio.

This signal chain is available as an evaluation board.

Other complementary parts include the ADRF6702 quadrature modulator and ADRF6602 Rx mixer.

The AD9122 low-voltage differential signalling (LVDS) interface with an eight-word-deep FIFO (first-in, first-out) memory supports a maximum sample-data-input-rate of 1.2GSPS and 600MSPS (mega samples per second) per DAC to support signal bandwidths up to 400MHz in advanced DPD transmitter architectures.

The data interface supports word, byte, and nibble load allowing customers to reduce input pins on lower data rates to save board space, power and cost.

The AD9122 includes an improved on-chip phased-locked loop (PLL) with lower jitter and phase noise.

Operating with the on-chip PLL at a DAC output frequency of 150MHz, the AD9122 delivers a 76-dB adjacent-channel leakage ratio for single-carrier WCDMA applications.

For demanding wireless communications applications, the AD9122 can achieve 83-dBc ACLR using an external PLL.

The combination of input data rates, high DAC sample rates, and fine modulation with the integrated NCO gives system designers flexibility when selecting DAC output frequencies.

This is said to be helpful in meeting four- to six-carrier GSM transmission specifications and other communications standards.

The AD9122 includes integrated interpolation filters with selectable interpolation factors of two, four, and eight.

The dual DAC also integrates 32-bit NCOs and is available in a 72-pin LFCSP (lead-frame chip-scale package) that is 50 per cent smaller than previous-generation DACs.

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