AD5263BRUZ200-R7 datasheet(22/28 Pages) AD

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AD5263

Data Sheet

Rev. F | Page 22 of 28

VLOGIC POWER SUPPLY

The AD5263 is capable of operating at high voltages beyond the

internal logic levels, which are limited to operation at 5 V. As a

result, VL always needs to be tied to a separate 2.7 V to 5.5 V source

to ensure proper digital signal levels. Logic levels must be limited to

VL, regardless of VDD. In addition, VL should always be less than

or equal to VDD.

LAYOUT AND POWER SUPPLY BYPASSING

It is a good practice to employ compact, minimum-lead length

layout design. The leads to the input should be as direct as possible

with a minimum conductor length. Ground paths should have

low resistance and low inductance.

Similarly, it is also a good practice to bypass the power supplies

with quality capacitors for optimum stability. Supply leads to

the device should be bypassed with 0.01 µF to 0.1 µF ceramic

disc or chip capacitors. Low ESR 1 µF to 10 µF tantalum or

electrolytic capacitors should also be applied at the supplies to

minimize any transient disturbance and low frequency ripple

(see Figure 55). Notice the digital ground should also be joined

remotely to the analog ground at one point to minimize the

ground bounce.

GND

VSS

VDD

AD5263

VSS

VDD

0.1µF

10µF

Figure 55. Power Supply Bypassing

RDAC CIRCUIT SIMULATION MODEL

The internal parasitic capacitances and the external capacitive loads

dominate the ac characteristics of the RDACs. Configured as a

potentiometer divider, the –3 dB bandwidth of the AD5263 (20 kΩ

resistor) measures 300 kHz at half scale. Figure 22 provides the

large signal BODE plot characteristics of the three available

resistor versions: 20 kΩ, 50 kΩ, and 200 kΩ. A parasitic simulation

model is shown in Figure 56. The following code provides a

macro model net list for the 20 kΩ RDAC.

20kΩ

25pF

RDAC

25pF

55pF

Figure 56. RDAC Circuit Simulation Model for RDAC = 20 kΩ

Listing 1. Macro Model Net List for RDAC

.PARAM D=256, RDAC=20E3

.SUBCKT DPOT (A,W,B)

25E-12

RWA

{(1-D/256)*RDAC+60}

55E-12

RWB

{D/256*RDAC+60}

25E-12

.ENDS DPOT

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