AD5602 datasheet(21/24 Pages) AD

21 / 24 page

Data Sheet

AD5602/AD5612/AD5622

APPLICATIONS INFORMATION

analog.com

Rev. F | 21 of 24

CHOOSING A REFERENCE AS POWER

SUPPLY

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

ages 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 appli-

cations. 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.

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 oper-

ation, 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

úû

êë

(2)

where:

D represents the input code in decimal.

n represents the bit resolution of the DAC.

With VDD = 5 V, R1 = R2 = 10 kΩ.

æ ´

(3)

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.

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 the AD5602, 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.

AD5602 Datasheet(PDF) 21 Page - Analog Devices

AD5602 Datasheet(HTML) 21 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Datasheet Download

Link URL