AN-1225: 32 Channels of Programmable Voltage with Excellent Temperature Drift Performance Using the AD5382 DAC

下载 PDF

Circuit Function and Benefits

This circuit is a multichannel digital-to-analog converter (DAC) configuration with excellent temperature drift performance. It provides 32 individual voltage channels with 14 bits of resolution and a temperature stability of typically less than 3 ppm/°C.

Circuit Description

Table 1. Devices Connected/Referenced
Product Description
AD5382 32-channel 14-bit 3 V/5 V single-supply DAC
ADR421 Low noise, 2.500 V XFET® voltage reference
ADR431 Ultralow noise XFET voltage reference

Figure 1 shows a typical configuration for the AD5382 when configured for use with an external reference. In the circuit shown, all AGND, SIGNAL_GND, and DAC_GND pins are tied together to a common AGND. AGND and DGND are connected together at the AD5382 device. On power-up, the AD5382 defaults to external reference operation.

Figure 1. AD5382 Typical Configuration with External Reference (Simplified Schematic)

Figure 1. AD5382 Typical Configuration with External Reference (Simplified Schematic)

This design uses two separate 5.0 V power supplies: one to power the voltage reference and the analog portion of the AD5382 (AVDD), and the other to power the digital portion of the AD5382 (DVDD). For best performance, always use a linear regulator to power the analog portion of the circuit. If a switching regulator is used to power the digital portion, take care to minimize switching noise at the DVDD supply pins. Additional decoupling using a series connected ferrite bead may be required. The AD5382 digital (DVDD) power supply can operate from a 3 V or 5 V supply, which provides for maximum flexibility when interfacing to digital components. Both supplies can be tied together to a common 5 V supply, provided that supply is derived from a linear regulator. Refer to the ADIsimPower design tool for guidance on the power supply designs.

It is recommended to decouple close to the device with a 0.1 µF ceramic and a 10 µF tantalum capacitor. In this circuit, the reference for the AD5382 is provided externally from either an ADR421 or ADR431 2.5 V reference. The ADR431 provides a lower output voltage noise specification for applications where that specification is important. Decouple the reference at the REFOUT/REFIN pin of the device with a 0.1 µF capacitor.

Common Variations

A variation of this circuit is the AD5382-3 with the ADR280 1.2 V reference where all other connections and components are the same as those previously outlined.