DAC8830-EP_16 Datasheet, PDF (21/32 Pages) Texas Instruments – 16-Bit, Ultra-Low Power, Voltage-Output Digital-to-Analog Converters

DAC8830-EP
DAC8831-EP
www.ti.com
SGLS334C – AUGUST 2006 – REVISED APRIL 2007
Bipolar Output Operation
With the aid of an external operational amplifier, the DAC8831 may be configured to provide a bipolar voltage
output. A typical circuit of such an operation is shown in Figure 48. 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.
Table 2 shows the transfer function for this output operating mode. The DAC8831 also provides a set of Kelvin
connections to the analog ground and external reference inputs.
Table 2. Bipolar Code
DAC Latch Contents
MSB
LSB
1111 1111 1111 1111
1000 0000 0000 0000
0111 1111 1111 1111
0000 0000 0000 0001
0000 0000 0000 0000
Analog Output
V_REF × (32,767/32,768)
V_REF × (1/32,768)
0V
–V_REF × (1/32,768)
–V_REF × (32,767/32,768) = –V_REF
+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
DAC8831
+V
V_O = −V_REF to +V_REF
OPA277
−V OPA704
OPA727
Figure 48. Bipolar Output Mode of DAC8831
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
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