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INTEGRAL AND DIFFERENTIAL LINEARITY

GLITCH ENERGY

CHANNEL-TO-CHANNEL CROSSTALK

APPLICATION INFORMATION

Waveform Generation

Generating ±5-V, ±10-V, and ± 12-V Outputs For

DAC7553

VREFH

DAC7553

Vdac

REF3140

VREF

Vtail

VOUT

OPA130

DAC7553

SLAS477 – SEPTEMBER 2005

each DAC step determines the minimum incremental

change the loop can generate. A DNL error less than

The DAC7553 uses precision thin-film resistors

–1 LSB (non-monotonicity) can create loop instability.

providing

exceptional

linearity

and

monotonicity.

DNL

error

greater

than

LSB

implies

Integral linearity error is typically within (+/-) 0.35

unnecessarily large voltage steps and missed voltage

LSBs, and differential linearity error is typically within

targets. With high DNL errors, the loop loses its

(+/-) 0.08 LSBs.

stability, resolution, and accuracy. Offering 12-bit

ensured monotonicity and ± 0.08 LSB typical DNL

error, 755X DACs are great choices for precision

control loops.

The DAC7553 uses a proprietary architecture that

minimizes glitch energy. The code-to-code glitches

Loop Speed:

are so low, they are usually buried within the

Many factors determine control loop speed. Typically,

wide-band noise and cannot be easily detected. The

the conversion time of the ADC and the computation

DAC7553 glitch is typically well under 0.1 nV-s. Such

time of the MCU are the two major factors that

low

glitch

energy

provides

than

10X

dominate the time constant of the loop. DAC settling

improvement over industry alternatives.

time is rarely a dominant factor because ADC

conversion times usually exceed DAC conversion

times. DAC offset, gain, and linearity errors can slow

The DAC7553 architecture is designed to minimize

the loop down only during the start-up. Once the loop

channel-to-channel crosstalk. The voltage change in

reaches its steady-state operation, these errors do

one channel does not affect the voltage output in

not affect loop speed any further. Depending on the

another channel. The DC crosstalk is in the order of a

ringing characteristics of the loop's transfer function,

few microvolts. AC crosstalk is also less than –100

DAC glitches can also slow the loop down. With its 1

dBs. This provides orders of magnitude improvement

MSPS (small-signal) maximum data update rate,

over certain competing architectures.

DAC7553 can support high-speed control loops.

Ultralow glitch energy of the DAC7553 significantly

improves loop stability and loop settling time.

Generating Industrial Voltage Ranges:

For control loop applications, DAC gain and offset

Due to its exceptional linearity, low glitch, and low

errors are not important parameters. This could be

crosstalk, the DAC7553 is well suited for waveform

exploited to lower trim and calibration costs in a

generation (from DC to 10 kHz). The DAC7553

high-voltage

control

circuit

design.

Using

large-signal settling time is 5 µs, supporting an

operational

amplifier

(OPA130),

and

voltage

update rate of 200 KSPS. However, the update rates

reference (REF3140), the DAC7553 can generate the

can exceed 1 MSPS if the waveform to be generated

wide voltage swings required by the control loop.

consists of small voltage steps between consecutive

DAC updates. To obtain a high dynamic range,

REF3140

(4.096

REF02

are

recommended for reference voltage generation.

Precision Industrial Control

Industrial control applications can require multiple

feedback loops consisting of sensors, ADCs, MCUs,

DACs, and actuators. Loop accuracy and loop speed

are the two important parameters of such control

loops.

Figure 31. Low-cost, Wide-swing Voltage

Generator for Control Loop Applications

Loop Accuracy:

In a control loop, the ADC has to be accurate. Offset,

The output voltage of the configuration is given by:

gain, and the integral linearity errors of the DAC are

not factors in determining the accuracy of the loop.

As long as a voltage exists in the transfer curve of a

monotonic DAC, the loop can find it and settle to it.

On the other hand, DAC resolution and differential

linearity do determine the loop accuracy, because

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