Datasheet

DAC101C081
V
OUT
0.1 PF
+
10 PF
+
-
+5V
R
1
R
2
-5V
+5V
±5V
10 pF
SDA
SCL
DAC101C081, DAC101C081Q, DAC101C085
www.ti.com SNVS801A –APRIL 2012–REVISED MARCH 2013
BIPOLAR OPERATION
The DAC101C081 is designed for single supply operation and thus has a unipolar output. However, a bipolar
output may be obtained with the circuit in Figure 34. 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 34. Bipolar Operation
The output voltage of this circuit for any code is found to be:
V
O
= (V
A
x (D / 1024) x ((R1 + R2) / R1) - V
A
x R2 / R1)
where
• D is the input code in decimal form. (6)
With V
A
= 5V and R1 = R2,
V
O
= (10 x D / 1024) - 5V (7)
A list of rail-to-rail amplifiers suitable for this application are indicated in Table 3.
Table 3. Some Rail-to-Rail Amplifiers
AMP PKGS Typ V
OS
Typ I
SUPPLY
LMP7701 SOT-23-5 37 uV 0.79 mA
LMV841 SC70-5 50 uV 1 mA
LMC7111 SOT-23-5 0.9 mV 25 µA
SO-8
LM7301 0.03 mV 620 µA
SOT-23-5
LM8261 SOT-23-5 0.7 mV 1 mA
DSP/MICROPROCESSOR INTERFACING
Interfacing the DAC101C081 to microprocessors and DSPs is quite simple. The following guidelines are offered
to simplify the design process.
Interfacing to the 2-wire Bus
Figure 35 shows a microcontroller interfacing to the DAC101C081 via the 2-wire bus. Pull-up resistors (Rp)
should be chosen to create an appropriate bus rise time and to limit the current that will be sunk by the open-
drain outputs of the devices on the bus. Please refer to the I
2
C™ Specification for further details. Typical pull-up
values to use in Standard-Fast mode bus applications are 2kΩ to 10kΩ. SCL and SDA series resisters (R
S
) near
the DAC101C081 are optional. If high-voltage spikes are expected on the 2-wire bus, series resistors should be
used to filter the voltage on SDA and SCL. The value of the series resistance must be picked to ensure the V
IL
threshold can be achieved. If used, R
S
is typically 51Ω.
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