Dual-Channel DACs Help Conserve Power

Dec. 16, 2011
This pair of dual-channel data converters supports a wide range of commercial and military applications with stable, noise-free output signals as a result of sampling rates to 500 MSamples/s.
Model DAC3162 is a dual-channel digital-to-analog converter with low power consumption at sampling rates to 500 MSamples/s.

Digital-to-analog converters (DACs) are useful in signal generation for a wide range of applications, from consumer electronic devices to advanced military systems. Of course, when it comes to portable systems, power consumption is critical. A new pair of high-speed DACs from Texas Instruments, models DAC3152 and DAC3162, provide dual-channel operation at sampling rates to 500 Msamples/s while using a fraction of the power of competing DACs. Model DAC3152 provides 10-b resolution on both channels while model DAC3162 offers 12-b resolution.

With its acquisition of integrated-circuit (IC) innovator national semiconductor, Texas Instruments now supplies about 25% of the worldwide market for data converters. With the new DAC3152 and DAC3162 models, designers can implement such circuits as direct-digital synthesizers (DDSs) without the usual penalty in power consumption. the higher-resolution DAC3162, for example, consumes just 135 mW power per channel to supply 20 mA output current per channel, and just 67 mA per channel to deliver 2 mA output current per channel. Both DACs can interface directly with additional signal-processing ICs (such as the firm's model TRF370333 analog quadrature modulator) for simple direct-upconversion applications.

Both DACs are supplied in a 48-pin, 7 x 7 mm QFN package (see figure) and feature a simplified interface that eliminates the need for a serial peripheral interface (SPI). In fact, the converters can be operated via simple control, without need of software. The digital data for both DAC channels is interleaved through a single LVDS data bus with on-chip termination. each DAC features an on-chip 1.2-V reference and operates with +1.8 and +3.3 vDc supplies. the on-chip reference only suffers drift of 8 ppm/C.

In terms of performance, both DACs offer clean output signals with very little distortion. For example, the lower-resolution 10-b model DAC3152 achieves typical differential nonlinearity (DNL) of 0.25 least significant bit (SB) and integral nonlinearity (INL) of 0.50 LSB. the spurious-free dynamic range (SFDR) for the DAC3152 is typically −76 dBc for a single tone of 10 MHz, typically −71 dBc for a single tone of 20 MHz, and typically −67 dBc for a single tone of 70 MHz. For the 10-b converter, the third-order intermodulation distortion (IMD3) is typically −86 dBc for two tones at 10 0.5 MHz, typically −81 dBc for two tones at 20 0.5 MHz, and typically −72 dBc for two tones at 70 0.5 MHz. the DAC features typical noise spectral density of −154 dBm/ Hz at 10 MHz and 500 Msamples/s and typically −153 dBm/Hz at 70 MHz and 500 Msamples/s.

The higher-resolution, 12-b model DAC3162 boasts typical DNL of 0.1 LSB and inl of 0.25 LSB. It delivers SFDR of typically −78 dBc for a single tone at 10 MHz, typically −73 dBc for single tone at 20 MHz, and typically −68 dBc for single tone at 70 MHz. It offers IMD3 performance of −86 dBc for two tones at 10 0.5 MHz, typically −83 dBc for two tones at 20 0.5 MHz, and typically −73 dBc for two tones at 70 0.5 MHz. The 12-b converter's noise spectral density is typically −157 dBm/Hz at 10 MHz and 500 Msamples/s sampling rate and typically −154 dBm/Hz at 70 MHz and 500 Msamples/s.

Both converters are specified for coarse-gain linearity of typically 0.04 LSB, gain error of 2% of full-scale reading (FSR), and gain-mismatch of 2% FSR. Each one is characterized by output resistance of 300 kΩ and output capacitance of typically 5 pF. In terms of the time domain, output signals achieve 10-ns settling time at a 500-MSamples/s sampling rate, with 220-ps typical rise/fall times for both converters. Both have low latency of 1.5 clock cycles. Both data converters can be used at operating temperatures from −40 to +85c. P&A: $12.60 (DAC3162) and $9.15 (DAC3152; 1000 qty.); stock.

About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

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