AS1504 Datasheet, PDF (13/17 Pages) ams AG – Octal 8-Bit Programmable Low-Power DACs with Shutdown and Mid-Scale Reset

AS1504, AS1505
Data Sheet
Figure 20. Output Buffering
+5V
VREFH
VDD
VREFL
VH
DAC1
VL
VH
DAC2
VL
VH
DAC3
VL
AS1504/
AS1505
GND
R1
100kΩ
Amplifier
+
–
+
–
austriamicrosystems
Increasing Output Voltage Swing
Simple Buffer
0 to 5V
Summer Circuit with
Fine Trim Adjustment
Increasing Output Voltage Swing
An external amplifier can be used to extend the output voltage swing beyond the power supply rails of the AS1504/
AS1505. This design allows for a simple digital interface to the DAC, while expanding the output swing to take advan-
tage of higher voltage external power supplies (e.g., DAC 1 of Figure 21 is configured to swing from -5 to +5V). The
actual output voltage is given by:
VOUT = (1+ (RF/RS))((D/256)5V) - 5V
(EQ 3)
Where:
D is the DAC input value (i.e., 0 to 255).
This design can be combined with the circuit in Figure 20 if very accurate adjustments around 0V are required.
Figure 21. Increasing Output Voltage Swing
+5V
RS
100kΩ
RF
100kΩ
VDD
VREFH
DAC1
AS1504/
AS1505
DAC2
OUT1
OUT2
GND
VREFL
AS1505
Only
+5V
–
+
-5V
+12V
+
–
100kΩ
100kΩ
-5 to +4.98V
0 to +10V
DAC 2 (non-inverting AV = 2 configuration) of Figure 21 increases the available output swing to +10V. The feedback
resistors can be adjusted to provide scaling of the output voltage, within the limits of the external operational amplifier
power supplies.
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Revision 1.0
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