ALLGEMEINE BESCHREIBUNG

The AD9744 is a 14-bit resolution, wideband, third generation member of the TxDAC series of high performance, low power CMOS digital-to-analog converters (DACs). The TxDAC family, consisting of pin-compatible 8-, 10-, 12-, and 14-bit DACs, is specifically optimized for the transmit signal path of communication systems. All of the devices share the same interface options, small outline package, and pinout, providing an upward or downward component selection path based on performance, resolution, and cost. The AD9744 offers exceptional ac and dc performance while supporting update rates up to 210 MSPS.
The AD9744’s low power dissipation makes it well suited for portable and low power applications. Its power dissipation can be further reduced to a mere 60 mW with a slight degradation in performance by lowering the full-scale current output. Also, a power-down mode reduces the standby power dissipation to approximately 15 mW. A segmented current source architecture is combined with a proprietary switching technique to reduce spurious components and enhance dynamic performance.
Edge-triggered input latches and a 1.2 V temperature compensated band gap reference have been integrated to provide a complete monolithic DAC solution. The digital inputs support 3 V CMOS logic families.

 

PRODUKT-HIGHLIGHTS

1. The AD9744 is the 14-bit member of the pin compatible TxDAC family, which offers excellent INL and DNL performance.
2. Data input supports twos complement or straight binary data coding.
3. High speed, single-ended CMOS clock input supports 210 MSPS conversion rate.
4. Low power: Complete CMOS DAC function operates on 135 mW from a 2.7 V to 3.6 V single supply. The DAC fullscale current can be reduced for lower power operation, and a sleep mode is provided for low power idle periods.
5. On-chip voltage reference: The AD9744 includes a 1.2 V temperature compensated band gap voltage reference.
6. Industry-standard 28-lead SOIC, 28-lead TSSOP, and 32-lead LFCSP packages.

 

FEATURES

High performance member of pin-compatible TxDAC product family
Excellent spurious-free dynamic range performance
SFDR to Nyquist
83 dBc at 5 MHz output
80 dBc at 10 MHz output
73 dBc at 20 MHz output
SNR at 5 MHz output, 125 MSPS: 77 dB
Twos complement or straight binary data format
Differential current outputs: 2 mA to 20 mA
Power dissipation: 135 mW at 3.3 V
Power-down mode: 15 mW at 3.3 V
On-chip 1.2 V reference
CMOS-compatible digital interface
28-lead SOIC, 28-lead TSSOP, and 32-lead LFCSP packages
Edge-triggered latches

 

ANWENDUNGEN

Wideband communication transmit channel Direct IFs
Base stations
Wireless local loops
Digital radio links
Direct digital synthesis (DDS)
Instrumentierung

 

TERMINOLOGIE

Linearitätsfehler (auch Integrale Nichtlinearität oder INL genannt)

It is defined as the maximum deviation of the actual analog output from the ideal output, determined by a straight line drawn from zero to full scale.

Differential Nonlinearity (or DNL)

DNL ist das Maß für die Veränderung des Analogwerts, normiert auf den vollen Skalenwert, die mit einer Änderung des digitalen Eingangscodes um 1 LSB einhergeht.

Monotonie

A DAC is monotonic if the output either increases or remains constant as the digital input increases.

Offset-Fehler

The deviation of the output current from the ideal of zero is called the offset error. For IOUTA, 0 mA output is expected when the inputs are all 0s. For IOUTB, 0 mA output is expected when all inputs are set to 1s.

Verstärkungsfehler

The difference between the actual and ideal output span. The actual span is determined by the output when all inputs are set to 1s minus the output when all inputs are set to 0s.

Output Compliance Bereich

The range of allowable voltage at the output of a current output DAC. Operation beyond the maximum compliance limits may cause either output stage saturation or breakdown, resulting in nonlinear performance.

Temperaturdrift

It is specified as the maximum change from the ambient (25°C) value to the value at either TMIN or TMAX. For offset and gain drift, the drift is reported in ppm of full-scale range (FSR) per °C. For reference drift, the drift is reported in ppm per °C.