Understanding the Specifications–AD589

VOLTAGE VARIATION VS. TEMPERATURE

Some confusion exists in the area of defining and specifying

reference voltage error over temperature. Historically, references

have been characterized using a maximum deviation per degree

Centigrade; i.e., 10 ppm/

°C. However, because of nonlinearities

in temperature characteristics, which originated in standard

Zener references (such as “S” type characteristics) most

manufacturers have begun to use a maximum limit error band

approach to specify devices. This technique involves measure-

ment of the output at 3, 5 or more different temperatures to

guarantee that the output voltage will fall within the given error

band. The temperature characteristics of the AD589 consis-

tently follows the curve shown in Figure 1. Three-point

measurement guarantees the error band over the specified

temperature range. The temperature coefficients specified on

the previous page represent the slopes of the diagonals of the

error band from +25

°C to T

1.2370

1.2345

+125

1.2360

1.2350

–25

1.2355

–50

1.2365

+100

+75

+50

+25

0

TEMPERATURE – °C

Figure 1. Typical AD589 Temperature Characteristics

1000

100

0

10

100

1M

100k

10k

1k

10

FREQUENCY – Hz

Figure 2. Noise Spectral Density

DYNAMIC PERFORMANCE

Many low power instrument manufacturers are becoming

increasingly concerned with the turn-on characteristics of the

components being used in their systems. Fast turn-on compo-

nents often enable the end user to keep power off when not

needed, and yet respond quickly when the power is turned on

for operation. Figure 3 displays the turn-on characteristics of the

AD589. This characteristic is generated from cold-start opera-

tion and represents the true turn-on waveform after an extended

period with the supplies off. The figure shows both the coarse

and fine transient characteristics of the device; the total settling

time to within

±1 millivolt is about 25 µs, and there is no long

thermal tail appearing after that point.

10

90

100

0%

200mV

10µs

10mV

Figure 3. Output Settling Characteristics

R1

R5

R6

R2

R7

C1

Q2

R4

Q1

R3

Q3

Q4

–V

+V

Q5

Q8

Q7

Q9

Figure 4. Schematic Diagram

REV.B

–3–