Datasheet

AD5641 Data Sheet
Rev. D | Page 16 of 20
APPLICATIONS
CHOOSING A REFERENCE AS POWER SUPPLY FOR
THE AD5641
The AD5641 comes in tiny LFCSP and SC70 packages with less
than 100 μA supply current. Because of this, the choice of refer-
ence depends on the application requirement. For space-saving
applications, the ADR02 is available in an SC70 package and
has excellent drift at 9 ppm/°C (3 ppm/°C in the R-8 package).
It also provides very good noise performance at 3.4 μV p-p in
the 0.1 Hz to 10 Hz range.
Because the supply current required by the AD5641 is
extremely low, the parts are ideal for low supply applications.
The ADR395 voltage reference is recommended in this case.
It requires less than 100 μA of quiescent current and can,
therefore, drive multiple DACs in one system, if required. It
also provides very good noise performance at 8 μV p-p in the
0.1 Hz to 10 Hz range.
AD5641
3-WIRE
SERIAL
INTERFACE
SYNC
SCLK
SDIN
7V
5V
V
OUT
= 0V TO 5V
ADR395
04611-041
Figure 43. ADR395 as Power Supply to AD5641
Table 7 lists some recommended precision references for use as
supplies to the AD5641.
Table 7. Precision References for Use with AD5641
Part No.
Initial
Accuracy
(mV max)
Temperature
Drift
(ppm/°C max)
0.1 Hz to 10 Hz
Noise (μV p-p typ)
ADR435 ±2 3 (R-8) 8
ADR425 ±2 3 (R-8) 3.4
ADR02 ±3 3 (R-8) 10
ADR02 ±3 3 (SC70) 10
ADR395 ±5 9 (TSOT-23) 8
BIPOLAR OPERATION USING THE AD5641
The AD5641 has been designed for single-supply operation,
but a bipolar output range is also possible using the circuit in
Figure 44. The circuit in Figure 44 gives an output voltage
range of ±5 V. Rail-to-rail operation at the amplifier output is
achievable using an AD820 or OP295 as the output amplifier.
R2 = 10k
04611-042

+5V
–5V
AD820/
OP295
3-WIRE
SERIAL
INTERFACE
+5V
AD5641
10F
0.1F
V
DD
V
OUT
R1 = 10k
+5V
Figure 44. Bipolar Operation with the AD5641
The output voltage for any input code can be calculated as
































R1
R2
V
R1
R2R1D
VV
DDDD
OUT
384,16
where
D represents the input code in decimal (0 – 16384).
With V
DD
= 5 V, R1 = R2 = 10 kΩ,
V5
384,16
10











D
V
OUT
This is an output voltage range of ±5 V with 0x0000 corre-
sponding to a –5 V output, and 0x3FFF corresponding to a
+5 V output.