Datasheet

DAC084S085
DIN
SCLK
SYNC
V
OUT
0.1 PF
+
10 PF
+
-
+5V
R
1
R
2
-5V
+5V
±5V
10 pF
LP2980
1 PF
Input
Voltage
ON /
OFF
V
IN
V
OUT
V
OUT
= 0V to 5V
DAC084S085
DIN
SCLK
SYNC
V
A
V
REFIN
0.1 PF
DAC084S085
SNAS363E –MAY 2006–REVISED MARCH 2013 www.ti.com
Figure 34. Using the LP2980 Regulator
Like any low dropout regulator, the LP2980 requires an output capacitor for loop stability. This output capacitor
must be at least 1.0µF over temperature, but values of 2.2µF or more will provide even better performance. The
ESR of this capacitor should be within the range specified in the LP2980 data sheet. Surface-mount solid
tantalum capacitors offer a good combination of small size and ESR. Ceramic capacitors are attractive due to
their small size but generally have ESR values that are too low for use with the LP2980. Aluminum electrolytic
capacitors are typically not a good choice due to their large size and have ESR values that may be too high at
low temperatures.
BIPOLAR OPERATION
The DAC084S085 is designed for single supply operation and thus has a unipolar output. However, a bipolar
output may be obtained with the circuit in Figure 35. This circuit will provide an output voltage range of ±5 Volts.
A rail-to-rail amplifier should be used if the amplifier supplies are limited to ±5V.
Figure 35. Bipolar Operation
The output voltage of this circuit for any code is found to be
V
O
= (V
A
x (D / 256) x ((R1 + R2) / R1) - V
A
x R2 / R1) (5)
where D is the input code in decimal form. With V
A
= 5V and R1 = R2,
V
O
= (10 x D / 256) - 5V (6)
A list of rail-to-rail amplifiers suitable for this application are indicated in Table 2.
Table 2. Some Rail-to-Rail Amplifiers
AMP PKGS Typ V
OS
Typ I
SUPPLY
DIP-8
LMC7111 0.9 mV 25 µA
SOT23-5
SO-8
LM7301 0.03 mV 620 µA
SOT23-5
LM8261 SOT23-5 0.7 mV 1 mA
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