DAC8420QBC AD [Analog Devices], DAC8420QBC Datasheet - Page 12

• Manufacturer Part Number: DAC8420QBC
• Description: Quad 12-Bit Serial Voltage Output DAC
• Manufacturer: AD [Analog Devices]

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
R3
5
1µF
R
B
9
6
A2
7
7
R2
A1
R1
10
8
6
R4
R5
Figure 28.
12
AD588
R6
4
11
3
13
A3
A4
10 V Bipolar Reference Configuration Using the AD588
+V
–V
S
S
16
14
15
1
2
0.1µF
0.1µF
+5V
–5V
+15V
SUPPLY
–15V
SUPPLY
SYSTEM
GROUND
–12–
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.
10
DIGITAL INPUTS
11
DAC-8420
12
CONTROL
DIGITAL
14
15 16
9
GND
DAC B
DAC C
DAC A
DAC D
5
+5V
VREFHI
4
VREFLO
–5V
–15V SUPPLY
+15V SUPPLY
8
1
7
6
3
2
0.1µF
VOUTC
VOUTA
VOUTB
VOUTD
0.1µF
REV. 0