REV. 0

AD5332/AD5333/AD5342/AD5343

–18–

Coarse and Fine Adjustment Using the AD5332/AD5333/

AD5342/AD5343

The DACs in the AD5332/AD5333/AD5342/AD5343 can be

paired together to form a coarse and fine adjustment function,

as shown in Figure 39. DAC A is used to provide the coarse

adjustment while DAC B provides the fine adjustment. Varying

the ratio of R1 and R2 will change the relative effect of the coarse

and fine adjustments. With the resistor values shown the output

amplifier has unity gain for the DAC A output, so the output

range is 0 V to 2.5 V – 1 LSB. For DAC B the amplifier has a gain

of 7.6

The circuit is shown with a 2.5 V reference, but reference volt-

rail-to-rail output swing.

Note that the AD5343 has only a single reference input. If using

the AD5332, AD5333, or AD5342, both reference inputs must

be connected.

GND

EXT

REF

AD780/REF192

R2

51.2k

+5V

0.1 F

0.1 F10 F

AD5332/AD5333/

AD5342/AD5343

GND

R1

390

*NOT AD5343

R4

390

R3

51.2k

Figure 39. Coarse and Fine Adjustment

Power Supply Bypassing and Grounding

In any circuit where accuracy is important, careful consideration

of the power supply and ground return layout helps to ensure

the rated performance. The printed circuit board on which the

AD5332/AD5333/AD5342/AD5343 is mounted should be

designed so that the analog and digital sections are separated,

and confined to certain areas of the board. If the device is in a

system where multiple devices require an AGND-to-DGND

connection, the connection should be made at one point only.

The star ground point should be established as closely as pos-

sible to the device. The AD5332/AD5333/AD5342/AD5343

should have ample supply bypassing of 10

µF in parallel with

0.1

µF on the supply located as close to the package as pos-

sible, ideally right up against the device. The 10

µF capacitors

are the tantalum bead type. The 0.1

µF capacitor should have

low Effective Series Resistance (ESR) and Effective Series Induc-

tance (ESI), like the common ceramic types that provide a low

impedance path to ground at high frequencies to handle tran-

sient currents due to internal logic switching.

The power supply lines of the device should use as large a trace

as possible to provide low impedance paths and reduce the effects

of glitches on the power supply line. Fast switching signals such

as clocks should be shielded with digital ground to avoid radiat-

ing noise to other parts of the board, and should never be run

near the reference inputs. Avoid crossover of digital and ana-

log signals. Traces on opposite sides of the board should run

at right angles to each other. This reduces the effects of feed-

through through the board. A microstrip technique is by far

the best, but not always possible with a double-sided board. In

this technique, the component side of the board is dedicated to

ground plane while signal traces are placed on the solder side.