Replacing the AD9764 with the GX9764 Single-Channel 14-Bit 125MSPS ADC for Communication Transmit Channels

The communication transmit channel is the complete signal chain in a communication system responsible for converting digital information into RF electromagnetic waves and transmitting them. The signal passes sequentially through digital baseband processing - DAC conversion - analog filtering - upconversion/modulation - power amplification - antenna radiation. The DAC is the digital-to-analog interface point in the transmit channel, and its dynamic performance determines the "noise floor" of the signal spectrum. Insufficient SFDR means spurs will appear directly in the RF spectrum; poor IMD means that multicarrier intermodulation products cannot be removed by subsequent filtering.

The ADC in the receive channel pursues the ability to capture weak signals in a noisy spectrum, while the DAC in the transmit channel faces a completely different challenge. The digital signal at the transmit end is modulated, filtered, and upconverted before being fed into the power amplifier, and its spectral purity directly determines the system‘s level of interference to adjacent channels.

The GX9764 single-channel 14-bit 125MSPS digital-to-analog converter has excellent SFDR and IMD performance and is specifically optimized for the transmit signal path of communication systems. The GX9764 provides excellent AC and DC performance while supporting update rates up to 125MSPS. It is manufactured using an advanced CMOS process and a segmented current source architecture, which reduces spurious components and improves dynamic performance. The GX9764 integrates an edge-triggered input latch and a 1.25V temperature-compensated bandgap reference to provide a complete monolithic DAC solution.

GX9764 Product Features:

• Single-channel 14-bit 125MSPS DAC

• Power consumption: 88mW (@3.3V)

• Single 3.3V power supply

• On-chip 1.25V reference

• Edge-triggered latch

• Differential current output: 2mA to 20mA

• Static performance: DNL -1.5/+1.5LSB, INL -2.5/+2.5LSB

• Dynamic performance:

fclock=25MSPS, fout=1.00MHz SFDR=72dBc

fclock=50MSPS, fout=1.00MHz SFDR=65dBc

fclock=50MSPS, fout=2.51MHz SFDR=70dBc

fclock=50MSPS, fout=5.02MHz SFDR=74dBc

fclock=50MSPS, fout=20.2MHz SFDR=65dBc