DAC8420_07 Datasheet, PDF (18/24 Pages) Analog Devices – Quad 12-Bit Serial Voltage Output DAC

DAC8420
is 16 mV. Thus, the best 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 30). A wide output voltage range can be
obtained with ±5 V references, which can be provided by the
1µF
AD588 as shown in Figure 33. Many applications utilize the
DACs to synthesize symmetric bipolar waveforms, which
require an accurate, low drift bipolar reference. The AD588
provides both voltages and needs no external components.
Additionally, the part is trimmed in production for 12-bit
accuracy over the full temperature range without user calibra-
tion. Performing a clear with the reset select CLSEL high allows
the user to easily reset the DAC outputs to midscale, or 0 V 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 a limited current sinking
capability 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.
+15V SUPPLY
7
6
4
3
AD588
R_B
A1
R1
R4
R2
R5
A3
1
14
A4
15
R3
A2
5 9 10
R6
8 12 11 13
+V_S 2
–V_S 16
0.1µF
0.1µF
+5V
–5V
+15V
SUPPLY
SYSTEM
GROUND
–15V
SUPPLY
DAC8420
VREFHI
+5V
5
1
0.1µF
DAC A
7
VOUTA
DAC B
6
VOUTB
DIGITAL
CONTROLS
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 33. ±10 V Bipolar Reference Configuration Using the AD588
–15V SUPPLY
Rev. B | Page 18 of 24