DAC8832 Datasheet, PDF (18/26 Pages) Texas Instruments – 16-Bit, Ultra-Low Power, Voltage-Output Digital-to-Analog Converter

DAC8832
SBAS380A – FEBRUARY 2006 – REVISED APRIL 2006
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BIPOLAR OUTPUT OPERATION
With the aid of an external operational amplifier, the DAC8832 may be configured to provide a bipolar voltage
output. A typical circuit of such an operation is shown in Figure 45. The matched bipolar offset resistors R_FB and
R_INV are connected to an external operational amplifier to achieve this bipolar output swing; typically, R_FB = R_INV
= 28 kΩ.
+5 V
+2.5 V
0.1 µF
+
0.1 µF
10 µF
LDAC
CS
SCLK
SDI
V_DD
V_REF−S V_REF−F
R_INV
R_FB
RFB
INV
Input
Register
DGND
DAC
DAC Latch
V_OUT
AGNDF
AGNDS
DAC8832
+V
V_O = −V_REF to +V_REF
OPA277
−V OPA704
OPA727
Figure 45. Bipolar Output Mode
Table 2 shows the transfer function for this output operating mode. The DAC8832 also provides a set of Kelvin
connections to the analog ground and external reference inputs.
Table 2. Bipolar Code
DAC LATCH CONTENTS
MSB
LSB
ANALOG OUTPUT
1111 1111 1111 1111
1000 0000 0000 0001
1000 0000 0000 0000
+V_REF × (32,767/32,768)
+V_REF × (1/32,768)
0V
0111 1111 1111 1111
0000 0000 0000 0000
–V_REF × (1/32,768)
–V_REF × (32,768/32,768) = –V_REF
Assuming a perfect reference, the worst-case output voltage may be calculated from the following equation:
Bipolar Mode Worst-Case Output:
ƪǒ Ǔ ƫ V_{OUT_UNI} ) V_OS (2 ) RD) * V_REF(1 ) RD)
V_{OUT_BIP} +
ǒ Ǔ _{1 )}
2)RD
A
Where:
V_OS = External operational amplifier input offset voltage
RD = R_FB and R_IN resistor matching error
A = Operational amplifier open-loop gain
18
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