AD5662ARM datasheet(16/20 Pages) AD

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AD5662

Preliminary Technical Data

Rev. PrA | Page 16 of 20

APPLICATIONS

USING REF19x AS A POWER SUPPLY FOR AD5662

Because the supply current required by the AD5662 is

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

reference (REF195 for 5 V, REF193 for 3 V) to supply the

required voltage to the part—see Figure 36. 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 AD5662.

If the low dropout REF195 is used, it must supply 250 µA of

current to the AD5662. 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

250 µA + (5 V/5 kΩ) = 1.25 mA

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

which results in a 2.5 ppm (12.5 µV) error for the 1.25 mA

current drawn from it. This corresponds to a 0.164 LSB error.

AD5662

THREE-WIRE

SERIAL

INTERFACE

SYNC

SCLK

DIN

+15V

+5V

250

µA

VOUT = 0V TO 5V

REF195

Figure 36. REF195 as Power Supply to AD5662

BIPOLAR OPERATION USING THE AD5662

The AD5662 has been designed for single-supply operation but

a bipolar output range is also possible using the circuit in

Figure 37. The circuit below gives 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:

⎥

⎦

⎤

⎢

⎣

⎡

⎟

⎠

⎞

⎜

⎝

⎛

−

⎟

⎠

⎞

⎜

⎝

⎛

⎟

⎠

⎞

⎜

⎝

⎛

536

where D represents the input code in decimal (0 to 65535).

With VDD = 5 V, R1 = R2 = 10 kΩ,

536

−

⎟

⎠

⎞

⎜

⎝

⎛

This is an output voltage range of ±5 V, with 0x0000 corre-

sponding to a −5 V output and 0xFFFF corresponding to a 5 V

output.

R2 = 10k

Ω

+5V

–5V

AD820/

OP295

THREE-WIRE

SERIAL

INTERFACE

+5V

AD5662

VDD

VOUT

R1 = 10k

Ω

±5V

0.1

µF

Figure 37. Bipolar Operation with the AD5662

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