DAC8420 Datasheet, PDF (12/16 Pages) Analog Devices – Quad 12-Bit Serial Voltage Output DAC

DAC8420
single supply operation is obtained with the output load
connected to ground, so the output stage does not have to sink
current.
Like all amplifiers, the DAC8420 output buffers do generate
voltage noise, 52 nV/√Hz typically. This is easily reduced by
adding a simple RC low-pass filter on each output.
Reference Configuration
The two reference inputs of the DAC8420 allow a great deal of
flexibility in circuit design. The user must take care, however, to
observe the minimum voltage input levels on VREFHI and
VREFLO to maintain the accuracy shown in the data sheet.
These input voltages can be set anywhere across a wide range
within the supplies, but must be a minimum of 2.5 V apart in
any case. See Figure 1. A wide output voltage range can be
obtained with ± 5 V references, which can be provided by the
AD588 as shown in Figure 28. Many applications utilize the
DACs to synthesize symmetric bipolar wave forms, which
requires an accurate, low drift bipolar reference. The AD588
provides both voltages and needs no external components. Ad-
ditionally, the part is trimmed in production for 12-bit accuracy
over the full temperature range without user calibration. Per-
forming a Clear with the reset select CLSEL HIGH allows the
user to easily reset the DAC outputs to midscale, or zero volts in
these applications.
When driving the reference inputs VREFHI and VREFLO, it is
important to note that VREFHI both sinks and sources current,
and that the input currents of both are code dependent. Many
voltage reference products have limited current sinking capabil-
ity and must be buffered with an amplifier to drive VREFHI, in
order to maintain overall system accuracy. The input VREFLO,
however, has no such requirement.
1µF
7
6
43
+15V SUPPLY
+5V
VREFHI
5
1
0.1µF
R_B
A1
R1
R2
R3
A2
5 96
10
AD588
R4
R5
A3
1
14
A4 15
R6
8 ¹² 11 13
+V_S ²
–V_S 16
0.1µF
0.1µF
+5V
–5V
+15V
SUPPLY
SYSTEM
GROUND
–15V
SUPPLY
DAC-8420
DAC A
DAC B
7
VOUTA
6
VOUTB
DIGITAL
CONTROL
DAC C
DAC D
3
VOUTC
2
VOUTD
10 11 12 14 15 16
DIGITAL INPUTS
9
4
8
GND ^VREFLO
–5V
0.1µF
Figure 28. ±10 V Bipolar Reference Configuration Using the AD588
–15V SUPPLY
–12–
REV. 0