AD680

Rev. H | Page 8 of 12

AD680

0V

249

Ω

0.1

μF

1000pF

Figure 12. Capacitive Load Transient Response Test Circuit

Figure 13 displays the output amplifier characteristics driving a

1,000 pF, 0 mA to 10 mA load.

100

90

0%

10

5

μs

5mV

2V

Figure 13. Output Response with Capacitive Load

LOAD REGULATION

Figure 14 depicts the load regulation characteristics of

the AD680.

100

90

0%

10

100

μs

1mV

1V

Figure 14. Typical Load Regulation Characteristics

TEMPERATURE PERFORMANCE

The AD680 is designed for reference applications where tem-

perature performance is important. Extensive temperature

testing and characterization ensure that the device’s performance

is maintained over the specified temperature range.

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, that is, ppm/°C. However, because of nonlinearities

in temperature characteristics that originated in standard Zener

references (such as “S” type characteristics), most manufac-

turers now use a maximum limit error band approach to specify

devices. This technique involves measuring the output at three

or more different temperatures to specify an output voltage

error band.

2.501

2.500

2.498

TEMPERATURE (

°C)

–50

60

020

40

2.499

–10

–30

80

100

SLOPE = TC

=

=

2.501 – 2.498

(85

°C – (–40°C))

= 9.6ppm/

°C

Figure 15. Typical AD680AN/AD680AR Temperature Drift

Figure 15 shows a typical output voltage drift for the AD680AN/

AD680AR and illustrates the test methodology. The box in

Figure 15 is bounded on the left and right sides by the operat-

ing temperature extremes, and on the top and bottom by the

maximum and minimum output voltages measured over the

operating temperature range.

The maximum height of the box for the appropriate temperature

range and device grade is shown in Table 4. Duplication of these

results requires a combination of high accuracy and stable tem-

perature control in a test system. Evaluation of the AD680 will

produce a curve similar to that in Figure 15, but output readings

could vary depending upon the test equipment used.

Table 4. Maximum Output Change in mV

Maximum Output Change (mV)

Device Grade

0°C to 70°C

−40°C to +85°C

AD680JN/AD680JR

4.375

Not applicable

AD680JT

5.250

Not applicable

AD680AN

Not applicable

6.250