Texas Instruments DAC8574, Руководство пользователя

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The Output Op-Amp
3-4
3.4.1 Unity Gain Output
The buffered output configuration can be used to prevent loading the
DAC8574, though it may present some slight distortion because of the
feedback resistor and capacitor. Users can tailor the feedback circuit to closely
match their desired wave shape by simply desoldering R7 and C11 and
replacing it with the desired values. You can also simply get rid of R7 and C11
altogether, and just solder a 0-
Ω
resistor in replacement of R7, if desired.
Table 3 - 3 shows the jumper setting for the unity gain configuration of the DAC
external output buffer in unipolar or bipolar mode.
Table 3 - 3. Unity Gain Output Jumper Settings
Jumper Setting
Reference
Unipolar Bipolar
Function
W3 OPEN OPEN Disconnect V
REF
H from the inverting input of the op-amp.
W5 2 - 3 1 - 2 Supplies V
SS
to the negative rail of op-amp or ties it to AGND.
W15 OPEN OPEN Disconnect negative input of op-amp from AGND.
3.4.2 Output Gain of Two
There are two types of configurations that yield a gain of two output depending
on the setup of the jumpers W3 and W15. These configurations allow the user
to choose whether the DAC output has V
REF
H as an offset or not.
Table 3 - 4 shows the proper jumper settings of the EVM for the 2
×
gain output
of the DAC.
Table 3 - 4. Gain of Two Output Jumper Settings
Jumper Setting
Reference
Unipolar Bipolar
Function
Close Close
Inverting input of the output op-amp, U2, is connected to V
REF
H for use
as its offset voltage with a gain of 2. W15 jumper must be open.
W3
Open Open
V
REF
H is disconnected from the inverting input of the output op-amp,
U2. W15 jumper must be close.
W5 2 - 3 1 - 2
Supplies power, V
SS
, to the negative rail of op-amp, U2, for bipolar
mode, or ties it to AGND for unipolar mode.
Close Close
Configures op-amp, U2, for a gain of 2 output without a voltage offset.
W3 jumper must be open.
W15
Open Open
Inverting input of the op-amp, U2, is disconnected from AGND. W3
jumper must be close.
3.4.3 Capacitive Load Drive
Another output configuration option is to drive a wide range of capacitive load
requirement. However, all op-amps under certain conditions may become
unstable depending on the op-amp configuration, gain, and load value. These
are just few factors that can affect op-amps stability performance and must be
considered when implementing.