Texas Instruments DAC8881, User Manual, Page: 14 / 25

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EVM Operation
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3.4.2 Output Gain of Two Operation
The jumper settings in Table 5 configure the EVM to operate with an output gain of two.
Table 5. Gain of Two Output Jumper Settings
Reference Jumper Setting Function
W9 1-2 Connects DAC output (V
OUT
1) to the non-inverting input of the output op-amp, U2.
2-3 Connects DAC output (V
OUT
2) to the non-inverting input of the output op-amp, U2.
W3 OPEN Disconnects V
REF
H to the inverting input of the op-amp, U2.
W5 1-2 Supplies power (V
SS
) to the negative rail of the op-amp, U2, for a wider range of operation.
W12 CLOSE Connects the negative input of the op-amp, U2, to the gain resistor, R12.
3.4.3 Capacitive Load Drive
Another output configuration option is to drive a wide range of capacitive loads. 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-amp stability performance and should be considered
during implementation.
In unity gain, the OPA627 op-amp, U2, performs very well with very large capacitive loads. Increasing the
gain enhances the ability of the amplifier to drive even more capacitance and by adding a load resistor
even improves the capacitive load drive capability.
Table 6 shows the jumper setting configuration for a capacitive load drive.
Table 6. Capacitive Load Drive Output Jumper Settings
Jumper
Reference Function
Setting
W9 1-2 Connects DAC output (V
OUT
1) to the non-inverting input of the output op-amp, U2.
2-3 Connects DAC output (V
OUT
2) to the non-inverting input of the output op-amp, U2.
W3 OPEN Disconnects V
REF
H to the inverting input of the op-amp, U2.
W5 1-2 Supplies power (V
SS
) to the negative rail of the op-amp, U2, for a wider range of operation.
W12 CLOSE Connects the negative input of the op-amp, U2, to the gain resistor, R12.
3.5 Jumper Settings
Table 7 shows the function of each specific jumper setting of the EVM.
Table 7. Jumper Setting Functions
Jumper
Reference Function
Setting
5VA for AV
DD
and DV
DD
to power the analog and digital supplies of the DAC8881.
W1
3.3VA for AV
DD
and DV
DD
to power the analog and digital supplies of the DAC8881.
Routes V
OUT
to J4-2.
W2
Routes V
OUT
to J4-6.
14 DAC8881 Evaluation Module SLAU257A – September 2008 – Revised November 2009
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