5

DAC80/80P

®

DISCUSSION OF

SPECIFICATIONS

DIGITAL INPUT CODES

The DAC80 accepts complementary binary digital input

codes. The CBI model may be connected by the user for any

one of three complementary codes: CSB, COB, or CTC (see

Table I).

ACCURACY

Linearity of a D/A converter is the true measure of its

performance. The linearity error of the DAC80 is specified

over its entire temperature range. This means that the analog

output will not vary by more than

±1/2LSB, maximum, from

an ideal straight line drawn between the end points (inputs

all “1”s and all “0”s) over the specified temperature range of

0

°C to +70°C.

Differential linearity error of a D/A converter is the devia-

tion from an ideal 1LSB voltage change from one adjacent

output state to the next. A differential linearity error speci-

fication of

±1/2LSB means that the output voltage step sizes

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

from one adjacent input state to the next.

Monotonicity over a 0

°C to +70°C range is guaranteed in the

DAC80 to insure that the analog output will increase or

remain the same for increasing input digital codes.

DRIFT

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

output over temperature expressed in parts per million per

°C (ppm/°C). Gain drift is established by: 1) testing the end

point differences for each DAC80 model at 0

°C, +25°C, and

+70

°C; 2) calculating the gain error with respect to the 25°C

value, and; 3) dividing by the temperature change. This

figure is expressed in ppm/

°C and is given in the electrical

specifications both with and without internal reference.

Offset Drift is a measure of the actual change in output with

all “1”s on the input over the specified temperature range.

The offset is measured at 0

°C, +25°C, and 70°C. The

maximum change in Offset is referenced to the Offset at

25

°C and is divided by the temperature range. This drift is

expressed in parts per million of full scale range per

°C (ppm

of FSR/

°C).

SETTLING TIME

Settling time for each DAC80 model is the total time

(including slew time) required for the output to settle within

an error band around its final value after a change in input

(see Figure 1).

Voltage Output Models

Three settling times are specified to

±0.01% of full scale

range (FSR); two for maximum full scale range changes of

20V, 10V and one for a 1LSB change. The 1LSB change is

measured at the major carry (0111...11 to 1000...00), the

point at which the worst case settling time occurs.

Current Output Models

Two settling times are specified to

±0.01% of FSR. Each is

given for current models connected with two different resis-

tive loads: 10

Ω to 100Ω and 1000Ω to 1875Ω. Internal

resistors are provided for connecting nominal load resis-

tances of approximately 1000

Ω to 1800Ω for output voltage

range of

±1V and 0 to –2V (see Figures 11 and 12).

COMPLIANCE

Compliance voltage is the maximum voltage swing allowed

on the current output node in order to maintain specified

accuracy. The maximum compliance voltage of all current

output models is

±2.5V. Maximum safe voltage range of

±1V and 0 to –2V (see Figures 11 and 12).

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 per percent of change in either

the positive or negative supplies about the nominal power

supply voltages (see Figure 2).

REFERENCE SUPPLY

All DAC80 models are supplied with an internal 6.3V

reference voltage supply. This voltage (pin 24) has a toler-

ance of

±1% and must be connected to the Reference Input

DIGITAL INPUT

ANALOG OUTPUT

CSB

COB

Complementary

Complementary Complementary

Straight

Offset

Two’s

MSB

LSB

Binary

Binary

Complement

↓↓

000000000000

+Full Scale

+Full Scale

–1LSB

011111111111

+1/2 Full Scale

Zero

–Full Scale

100000000000

1/2 Full Scale –1LSB

–1LSB

–Full Scale

111111111111

Zero

–Full Scale

Zero

NOTE: (1) Invert the MSB of the COB code with an external inverter to obtain

CTC code.

TABLE I. Digital Input Codes.

FIGURE 1. Full Scale Range Settling Time vs Accuracy.

0.1

Settling Time (µs)

1

10

100

1

0.3

0.1

0.03

0.01

0.003

0.001

R

10

Ω

to 100

Ω

R

1000

Ω

to 1875

Ω

10k

Ω

Feedback

5k

Ω

Feedback

V Models

I Models