Circuit functions and advantages
This circuit is a multi-channel DAC configuration with excellent temperature drift performance. It provides 40 independent output voltage channels with 12-bit resolution and temperature stability typically below 3 ppm/°C.
Figure 1 shows a typical configuration of the AD5381 with an external reference. In the circuit shown, all AGND, SIGNAL_GND, and DAC_GND pins are tied together and tied to a common AGND pin. On the AD5381 device, AGND and DGND are tied together. At power-up, the AD5381 operates with an external reference by default.
This design uses two separate 5.0 V supplies, one supplying the reference and the analog portion (AVDD) of the AD5381, and the other supplying the digital portion (DVDD) of the AD5381. For best performance, be sure to use a linear regulator to drive the analog portion of the circuit. If a switching regulator is used to drive the digital section, care should be taken to minimize switching noise on the DVDD supply pins. Additional decoupling with ferrite beads in series may also be required. The AD5381 digital (DVDD) power supply can take a 3 V or 5 V supply, which provides great flexibility when interfacing with digital components. If the power is obtained from a linear regulator, the two power pins can be tied together and connected to a common 5 V supply. Refer to the ADIsimPower™ Design Tool for guidelines on power supply design.
Figure 1. Typical AD5381 Configuration with External Reference (Simplified Schematic)
It is recommended to use 0.1 µF ceramic capacitors and 10 µF tantalum capacitors to decouple each power supply pin close to the device. In this circuit, the reference voltage for the AD5381 is obtained from an external 2.5 V reference, the ADR421 or ADR431. The low output voltage noise of the ADR431 makes it suitable for applications where this feature is particularly important. The reference should be decoupled with a 0.1 µF capacitor at the REFOUT/REFIN pins of the device.
A variation of this circuit uses the AD5381-3 (3 V device) and the ADR280 1.2 V reference, all other connections and components are the same as described above.
ADIsimPower Design Tool.
Kester, Walt. 2005. The Data Conversion Handbook. Analog Devices. Chapters 3 and 7.
MT-015 Tutorial, Basic DAC Architectures II: Binary DACs. Analog Devices.
MT-031 Tutorial, Grounding Data Converters and Solving the Mystery of AGND and DGND. Analog Devices.
MT-101 Tutorial, Decoupling Techniques. Analog Devices.
Voltage Reference Wizard Design Tool.
Datasheets and Evaluation Boards
AD5380/AD5381 Evaluation Board.
AD5381 Data Sheet.
ADR421 Data Sheet.
ADR431 Data Sheet.
5/09—Rev. 0 to Rev. A
Updated Format ……………………………………………………Universal
10/08—Revision 0: Initial Version