®

DAC811

4

TIMING DIAGRAMS

DISCUSSION OF

SPECIFICATIONS

INPUT CODES

The DAC811 accepts positive-true binary input codes.

DAC811 may be connected by the user for any one of the

following codes: USB (unipolar straight binary), BOB (bi-

polar offset binary) or, using an external inverter on the

MSB line, BTC (binary two’s complement). See Table I.

DRIFT

Gain drift is a measure of the change in the full scale range

(FSR) output over the specification temperature range. Drift is

expressed in parts per million per degree centigrade

(ppm/

°C). Gain drift is established by testing the full scale

range value (e.g., +FS minus –FS) at high temperature, +25

°C,

and low temperature, calculating the error with respect to the

+25

°C value, and dividing by the temperature change.

Unipolar offset drift is a measure of the change in output

with all 0s on the input over the specification temperature

range. Offset is measured at high temperature, +25

°C, and

low temperature. The offset drift is the maximum change in

offset referred to the +25

°C value, divided by the tempera-

ture change. It is expressed in parts per million of full scale

range per degree centigrade (ppm of FSR/

°C).

code that gives zero volts output for bipolar operation.

SETTLING TIME

Settling time is the total time (including slew time) for the

output to settle within an error band around its final value

after a change in input. Three settling times are specified to

±0.01% of full scale range (FSR): two for maximum full

scale range changes of 20V and 10V, and one for a 1LSB

change. The 1LSB change is measured at the major carry

which worst-case settling time occurs.

REFERENCE SUPPLY

DAC811 contains an on-chip 6.3V reference. This voltage

(pin 28) has a tolerance of

±0.1V. The reference output may

be used to drive external loads, sourcing at least 2mA. This

current should be constant for best performance of the D/A

converter.

POWER SUPPLY SENSITIVITY

Power supply sensitivity is a measure of the effect of a

power supply change on the D/A converter output. It is

defined as a percent of FSR output change per percent of

change in either the positive, negative, or logic supply

voltages about the nominal voltages. Figure 1 shows typical

power supply rejection versus power supply ripple frequency.

DIGITAL INPUT

ANALOG OUTPUT

USB

BOB

Unipolar

Bipolar

Binary

Straight

Offset

Two’s

Binary

Binary

Complement

111111111111

+ Full Scale

+ Full Scale

–1LSB

100000000000

+ 1/2 Full Scale

Zero

– Full Scale

011111111111

+ 1/2 Full Scale – 1LSB

–1LSB

+ Full Scale

000000000000

Zero

– Full Scale

Zero

NOTE: (1) Invert MSB of the BOB code with external inverter to obtain BTC code.

MSB

LSB

↓↓

TABLE I. Digital Input Codes.

LINEARITY ERROR

Linearity error as used in D/A converter specifications by

Burr-Brown is the deviation of the analog output from a

straight line drawn between the end points (inputs all 1s and

all 0s). The DAC811 linearity error is specified at

±1/4LSB

(max) at +25

°C for B and K grades, and ±1/2LSB (max) for

A, J, and R grades.

DIFFERENTIAL LINEARITY ERROR

Differential linearity error (DLE) is the deviation from a

1LSB output change from one adjacent state to the next. A

DLE specification of 1/2LSB means that the output step size

can range from 1/2LSB to 3/2LSB when the input changes

from one state to the next. Monotonicity requires that DLE

be less than 1LSB over the temperature range of interest.

MONOTONICITY

A D/A converter is monotonic if the output either increases

or remains the same for increasing digital inputs. All grades

of DAC811 are monotonic over their specification tempera-

ture range.

Load first rank from Data Bus: LDAC = 1

WR

N

t

AW

t

DW

t

DH

t

WP

DB

Write Cycle #1

t

SET

WR

±1/2LSB

LDAC

t

AW

t

WP

Load second rank from first rank: N

B

= 1

Write Cycle #2