Datasheet

31.6kW
1 Fm 1 Fm
1 Fm
1 Fm
0.1 Fm
100 Fm
(2)
1nF
1nF
50W
OPA211
50W
OPA211
TLV3491
-2.5V
-2.5V
-2.5V
-2.5V
+2.5V
+2.5V
+3.3V
+2.5V
+2.5V
-2.5V
+2.8V
+3.3V
GAIN[2:0]
PWDN
DVDD
CLKCLK
TDATATDATA
SYNCSYNC
VREF AVDD
RREF
AVSS
IOUTP
IOUTN
PWDN
1MW
DAC1280
REF5050
R
2k
A
W
(1)
2kW
R
B
(1)
-2.5V
1 Fm
1kW
(2)
1MW
100W
(2)
1MW
20 to 50W W
C0G/Film
C0G/Film
(1)
GAIN2
GAIN1
GAIN0
Controller
V
N
V
P
DAC1280
SBAS432A –APRIL 2010–REVISED SEPTEMBER 2010 www.ti.com
Basic Connection reference bias resistor is a 31.6kΩ precision resistor.
Increasing the resistor value (from 30kΩ nominal)
Figure 35 shows a basic connection of the DAC1280,
reduces the DAC full-scale output by –0.5db, to avoid
with an external op amp current-to-voltage converter.
clipping of the ADC. The filter series resistance and
Bipolar analog supplies are shown (±2.5V).
the VREF input impedance interaction results in a
Single-supply operation (+5V) is also possible by
gain error of –0.5%
grounding AVSS; for single-supply operation, bias the
current-to-voltage converter noninverting terminals to Two OPA211s and R
A
, R
B
implement the
midsupply. current-to-voltage converter. R
A
and R
B
scale the
DAC current output to a voltage output. 1nF
A low-noise, low-drift, precision reference is
capacitors filter the DAC sampling noise, and 50Ω
recommended for operation with the DAC1280, such
resistors isolate the op amp from capacitive loads.
as the REF5050. The REF5045 or REF02 are also
Place the current-to-voltage converter circuit
suitable, depending on the end system SNR
components close to the DAC1280 using a
requirements. The REF5045 operates from a
symmetrical layout. A comparator, such as the
minimum 5V power supply; the REF5050 operates
TLV3491, translates the PWDN logic level signal to
from a minimum 5.3V power supply; and the REF02
the OPA211 level requirements.
operates from a minimum 8.5V power supply. The
optional reference RC filter reduces broadband
reference noise. Using the filter network, loading of
the VREF input results in –0.5% gain error. The
(1) Precision resistors.
(2) Optional reference noise filter.
Figure 35. Basic Connection
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