CN0029| Application Note
Circuit Note
CN0029
A
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8-16 Channels of Programmable Voltage with Excellent Temperature Drift Performance Using the AD5390/AD5391/AD5392 DACs
Contributed November 7, 2008 Devices connected in this Circuit Note: AD5390/1/2 3V/5V 16 bit / 14 bit / 12 bit DAC ADR421/31 Precision Voltage References
Circuit Function and Benefits
The circuit described in this document and shown in Figure 1 is a multi-channel DAC configuration with excellent temperature drift performance. It utilizes the AD5390/1/2 to provide between 8 and 16 DAC channels with 12-14 bits of resolution. The ADR421/31 precision voltage reference ensures that the temperature stability of the circuit is typically less than 3ppm/C.
Circuit Description
The AD5390/AD5391 are complete single-supply, 16channel, 14-bit and 12-bit DACs, respectively. The AD5392 is a complete single-supply, 8-channel, 14-bit DAC. Devices are available both in 64-lead LFCSP and 52-lead LQFP packages. All channels have an on-chip output amplifier with rail-to-rail operation.
Figure 1: AD5390/1/2 Typical Configuration with External Reference
Figure 1 shows a typical configuration for the AD5390/1/2 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 AD5390/1/2 device. On power-up, the AD5390/1/2 defaults to external reference operation. This design uses two separate 5.0V power supplies one to power the voltage reference and the analog portion of the AD5390/1/2 (AVDD) and the other to power the digital portion of the AD5390/1/2 (DVDD). For best performance, a linear regulator should always be used to power the analog portion of the circuit. If a switching regulator is used to power the digital portion, care should be taken to minimize switching noise at the DVDD supply pins. The AD5390/1/2 digital (DVDD) power supply can operate off of a 3V or 5V supply which provides for maximum flexibility when interfacing to digital components. Both supplies can be tied together to a common 5V supply provided that suppl
y is derived from a linear regular. Refer to the ADIsimPower tool for guidance on the power supply designs. It is recommended to decouple close to the device with a 0.1 uF ceramic and a 10 uF tantalum capacitor. In this application, the reference for the AD5390/1/2 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. The reference should be decoupled at the REFOUT/REFIN pin of the device with a 0.1 uF capacitor.
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