Datasheet


SLAS353 − DECEMBER 2001
18
www.ti.com
APPLICATION INFORMATION
16 Bits
D[15:0]
CS
R/W
LDAC
V
REF
L
DGND
AV
DD
DV
DD
V
OUT
SENSE
V
OUT
V
REF
H
AGND
(Other Connections Omitted for Clarity)
0.1 µF 1 to 10 µF
0.1 µF 10 µF
0.1 µF 10 µF
AV
DD
DV
DD
V
OUT
V
REF
D[15:0]
A[23:0]
IOSTRB
R/W
XF(I/O)
TMS320C5402
DAC8541
Address
Decoder
EN
Figure 33. DAC8541 to TMS320 DSP
bipolar operation using the DAC8541
The DAC8541 has been designed for single-supply operation but a bipolar output range is also possible using
the circuit shown in Figure 34. The circuit allows the DAC8541 to achieve an analog output range of ±5 V.
Rail-to-rail operation at the amplifier output is achievable using an OPA703 as the output amplifier.
Setting BTC/USB
= 1, sets the DAC into binary 2s complement I/O format for the bipolar V
OUT
configuration.
When operated with BTC/USB
set high, the output voltage for any input code can be calculated as follows:
V
OUT
+
ƪ
V
REF
H
ǒ
D
65536
Ǔ ǒ
R1 ) R2
R1
Ǔ
* V
REF
H
ǒ
R2
R1
Ǔ
ƫ
where D represents the input code in decimal, unipolar straight binary (0–65535) and V
REF
L = AGND.
With V
REF
H = 5 V, R
1
= R
2
= 10 kΩ:
V
OUT
+
ǒ
10 D
65536
Ǔ
* 5V
This is an output voltage range of ±5 V with 8000h corresponding to a –5 V output and 7FFFh corresponding
to a 5 V output. Bipolar zero is given by 0000h applied to the DAC.
V
OUT
V
OUT
Sense
V
REF
H
V
REF
L
R1 = 10 kΩ
5 V
−5 V
R2 = 10 kΩ
±5 V
DAC8541
0.1 µF
10 µF
5 V
(Other Pins Omitted for Clarity)
OPA703
−
+
Figure 34. Bipolar Operation With the DAC8541