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Data Sheet

AD5602/AD5612/AD5622

Rev. E | Page 21 of 23

APPLICATIONS INFORMATION

CHOOSING A REFERENCE AS POWER SUPPLY

The AD5602/AD5612/AD5622 come in tiny LFCSP and SC70

packages with less than 100 µA supply current, thereby making

the choice of reference dependent upon the application

requirement. For space-saving applications, the ADR425 is

available in an SC70 package with excellent drift at 3ppm/°C. 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 AD5602/AD5612/

AD5622 DACs is extremely low, they are ideal for low supply

applications. The ADR293 voltage reference is recommended in

this case. This requires 15 µA of quiescent current and can

therefore drive multiple DACs in the one system, if required.

AD5602/

AD5612/

AD5622

SCL

SDA

VOUT = 0V TO 5V

ADR425

Figure 50. ADR425 as Power Supply

Examples of some recommended precision references for use as

supplies to the AD5602/AD5612/AD5622 are shown in Table 9.

Table 9. Recommended Precision References

Device

No.

Initial

Accuracy

(mV max)

Temperature

Drift

(ppm/°C max)

0.1 Hz to 10 Hz Noise

(µV p-p typ)

ADR435

±6

3.4

ADR425

±6

3.4

ADR02

±5

ADR395

±6

BIPOLAR OPERATION

The AD5602/AD5612/AD5622 are designed for single-supply

operation, but a bipolar output range is also possible using the

circuit in Figure 51. The circuit in Figure 51 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





















−

























where:

D represents the input code in decimal.

n represents the bit resolution of the DAC.

With VDD = 5 V, R1 = R2 = 10 kΩ.

−













This is an output voltage range of ±5 V with 0x000 corresponding

to a −5 V output, and 0xFFF corresponding to a +5 V output.

+5V

–5V

AD820/

OP295

+5V

AD5602/

AD5612/

AD5622

10µF

0.1µF

VDD

VOUT

10k

Ω

SDA SCL

10k

Ω

±5V OUT

Figure 51. Bipolar Operation with the AD5602/AD5612/AD5622

POWER SUPPLY BYPASSING AND GROUNDING

When accuracy is important in a circuit, it is helpful to carefully

consider the power supply and ground return layout on the board.

The printed circuit board containing the AD5602/AD5612/

AD5622 has separate analog and digital sections, each having its

own area of the board. If theAD5602, AD5612, or AD5622 is in

a system in which other devices require an AGND to DGND

connection, the connection is made at one point only. This ground

point must be as close as possible to the AD5602/AD5612/

AD5622.

The power supply to the AD5602/AD5612/AD5622 is bypassed

with 10 µF and 0.1 µF capacitors. The capacitors must be

physically as close as possible to the device with the 0.1 µF

capacitor ideally right up against the device. The 10 µF

capacitors are the tantalum bead type. It is important that the

0.1 µF capacitor has low effective series resistance (ESR) and

effective series inductance (ESI), such as common ceramic types.

This 0.1 µF capacitor provides a low impedance path to ground

for high frequencies caused by transient currents due to internal

logic switching.

The power supply line has as large a trace as possible to provide

a low impedance path and reduce glitch effects on the supply

line. Clocks and other fast switching digital signals must be

shielded from other devices of the board by digital ground.

Avoid crossover of digital and analog signals if possible. When

traces cross on opposite sides of the board, ensure they run at

right angles to each other to reduce feedthrough effects through the

board. The best board layout technique is the microstrip

technique where the component side of the board is dedicated

to the ground plane only and the signal traces are placed on the

solder side. However, the microstrip technique is not always

possible with a 2-layer board.

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