7

9/27/00

SPT5510

LONG-TERM STABILITY

VERSUS TEMPERATURE

As with all high-speed, high-resolution digital-to-analog con-

verters, the initial accuracy of the device will degrade with

both time and temperature. The graph shown in figure 7 can

be used to determine the expected change in linearity per-

formance over time when the device is operated at various

ambient temperatures. This graph shows how long it will

take for the SPT5510 linearity to change by 8 ppm (or 1/2

LSB) at any operating temperature. The top curve shown

represents integral nonlinearity (ILE) changes; the bottom

curve shows differential nonlinearity (DLE) changes.

Figure 7 – Linearity Performance over Time

Temperature (

°C)

Expected time required to produce an 8 ppm (1/2 LSB) linearity

(ILE or DLE) shift as a function of temperature.

0

20

40

60

80

100

120

1 month

1 year

100 years

1000 years

ILE

DLE

around 300 MHz, the amplifier’s phase crossover point. The

unity-gain bandwidth is roughly 700 MHz. Larger value

capacitors exhibit lower self-resonance frequency and thus

may not adequately compensate the reference amplifier.

Large capacitors may also introduce low frequency tails

which increase settling time. The DAC itself exhibits very

node, which can contribute to amplifier instability if not sup-

bypassed, as this will short all feedback to ground, leading

to severe oscillation.

Compensation must be optimized for each application. As

with any high-speed, high-resolution design, attention must

be paid to grounding, decoupling, and parasitic elements

that may cause instability. It may be wise to use a guard

ring, and/or clear the board ground, around the reference

amplifier’s inputs. All traces must be short, and capacitors

with high self-resonance must be used.

Compensation is perhaps the most challenging aspect of

setting up the SPT5510. By slowly switching a full-scale

data input (generating a low-frequency square wave), with

appropriate clock timing, the DAC’s output can be observed

using a suitable oscilloscope and spectrum analyzer to

observe and suppress any oscillations caused by board and

ther assistance if required.

PACKAGE OUTLINE

44-Lead MQFP

Index

A

B

C

D

Pin 1

E

F

G

H

I

J

K

INCHES

MILLIMETERS

SYMBOL

MIN

MAX

MIN

MAX

A

0.5098

0.5295

12.95

13.45

B

0.3917

0.3957

9.95

10.05

C

0.3917

0.3957

9.95

10.05

D

0.5098

0.5295

12.95

13.45

E

0.0311

0.0319

0.79

0.81

F

0.0118

0.0177

0.30

0.45

G

0.0768

0.0827

1.95

2.10

H

0.0039

0.0098

0.10

0.25

I

0.0287

0.0406

0.73

1.03

J

0.0630 REF

1.60 REF

K0

°

7

°

0

°

7

°

decoupling parasitics. Consult CADEKA Applications for fur-