AD5310

Data Sheet

Rev. B | Page 14 of 16

APPLICATIONS INFORMATION

USING REF19x AS A POWER SUPPLY FOR AD5310

Because the supply current required by the AD5310 is extremely

low, an alternative option is to use a REF19x voltage reference

(REF195 for 5 V or REF193 for 3 V) to supply the required voltage

to the part (see Figure 32). This is especially useful if the power

supply is quite noisy or if the system supply voltages are at some

value other than 5 V or 3 V (for example, 15 V). The REF19x

outputs a steady supply voltage for the AD5310. If the low dropout

REF195 is used, the current that it needs to supply to the AD5310

is 140 µA. This is with no load on the output of the DAC. When

the DAC output is loaded, the REF195 also needs to supply the

current to the load. The total current required (with a 5 kΩ load

on the DAC output) is

140 µA + (5 V/5 kΩ) = 1.14 mA

The load regulation of the REF195 is typically 2 ppm/mA, which

results in an error of 2.3 ppm (11.5 µV) for the 1.14 mA current

drawn from it. This corresponds to a 0.002 LSB error.

Figure 32. REF195 as Power Supply to AD5310

BIPOLAR OPERATION USING THE AD5310

The AD5310 is designed for single-supply operation but a bipolar

output range is also possible using the circuit shown in Figure 33.

This circuit results in an output voltage range of ±5 V. Rail-to-rail

operation at the amplifier output is achievable using an AD820

or an OP295 as the output amplifier. The output voltage for any

input code can be calculated as follows:





















×

−













+

×













×

=

R1

R2

V

R1

R2

R1

D

V

V

DD

DD

O

1024

where D represents the input code in decimal (0 to 1023).

V

5

1024

10

−











 ×

=

D

This is an output voltage range of ±5 V, with 000 hex corresponding

to a −5 V output and 3FF hex corresponding to a +5 V output.

Figure 33. Bipolar Operation with the AD5310

USING AD5310 WITH AN OPTO-ISOLATED

INTERFACE

In process control applications in industrial environments, it is

often necessary to use an opto-isolated interface to protect and

isolate the controlling circuitry from any hazardous common-

mode voltages that may occur in the area where the DAC is

functioning. Opto-isolators provide isolation in excess of 3 kV.

Because the AD5310 uses a 3-wire serial logic interface, it only

requires three opto-isolators to provide the required isolation

(see Figure 34). The power supply to the part also needs to be

isolated. This is done by using a transformer. On the DAC side

of the transformer, a 5 V regulator provides the 5 V supply required

for the AD5310.

Figure 34. AD5310 with an Opto-Isolated Interface