herunterladen
AN-1224
APPLICATION NOTE
One Technology Way • P. O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com
40 Channels of Programmable Voltage with Excellent Temperature Drift
Performance Using the AD5381 DAC
Rev. B | Page 1 of 2
CIRCUIT FUNCTION AND BENEFITS
This circuit is a multichannel digital-to-analog converter (DAC)
configuration with excellent temperature drift performance. It
provides 40 individual output voltage channels with 12 bits of
resolution and a temperature stability of typically less than
3 ppm/°C.
CIRCUIT DESCRIPTION
Table 1. Devices Connected/Referenced
Product Description
AD5381 40-channel 12-bit 3 V/5 V single-supply DAC
ADR421 Low noise, 2.500 V XFET® voltage references
ADR431 Ultralow noise XFET voltage references
Figure 1 shows a typical configuration for the AD5381 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 AD5381 device. On power-up, the
AD5381 defaults to external reference operation.
This design uses two separate 5.0 V power supplies: one to power
the voltage reference and the analog portion of the AD5381
(AVDD), and the other to power the digital portion of the
AD5381 (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, taken care to
minimize switching noise at the DVDD supply pins. Additional
decoupling using a series connected ferrite bead may be required.
The AD5381 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 each power pin close to the device
with a 0.1 µF ceramic and a 10 µF tantalum capacitor. In this
circuit, the reference for the AD5380 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 uses the AD5381-3 (3 V device) with
the ADR280 1.2 V reference where all other connections and
components are the same as those previously outlined.
08196-001
ADR431/
ADR421
AD5381-5
AVDD
2.5V
5.0V 5.0V
DVDD
SIGNAL_GNDDAC_GND
DGND
VOUT39
VOUT0
AGND
REFOUT/REFIN
REFGND
0.1µF
10µF 0.1µF
0.1µF
Figure 1. AD5381 Typical Configuration with External Reference (Simplified Schematic)
