Agilent Technologies 664xA, 665xA, 667xA, 668xA, AGILENT Model 6653A: 3145A-00551, Model 6641A: 3217A-00111, Model 6645A: 3215A-00111, Model 6651A: 3130A-00171, Model 6652A: 3201A-00381, Model 6654A: 3148A-00391, Model 6655A: 3152A-00176, Model 6671A: 3129A-00218, Model 6672A: 3138A-00101, Model 6673A: 3138A-00101, Model 6674A: 3133A-00161, Model 6675A: 3138A-00101, Model 6680A: 3302A-00101, Model 6681A: 3250A-00101, Model 6682A: 3339A-00101, Model 6683A: 3339A-00161, Model 6684A: 3339A-00101

Current Loop Compensation (Series 668xA Only) 125

Current Loop Compensation (Series 668xA Only)

This section describes how you may use current loop compensation to optimize for inductive loads or for fast CV/CC mode

crossover. A 7-position compensation switch for this purpose is located under the cover on the rear of the power supply.

Function Of Loop Compensation

Figure E-1 shows the switch settings for specific combinations of load inductance and resistance. Two sets of curves show

the small-signal response for each model. The dashed curves represent programming performance of no more than 10%

current overshoot. The solid curves represent operating conditions with 25% overshoot. The curve obtained with all

switches open gives the fastest CC mode crossover response time. However, as shown by these curves, the loop will not

tolerate larger inductances unless the load resistance is increased. The curve described when all switch positions are closed

shows the as-shipped performance curve. This position provides 10% overshoot and fast CV/CC crossover performance for

load inductances that are specific for each model. (For Models 6680A and 6681A, this curve ranges from 100 µohms at

15 µhenries to about 100 milliohms at 40 millihenries.). You can select a different compensation curve by opening a

specific switch or combination of switches.

Table E-1 shows some specific L ÷ R ratios and the switch positions required for these ratios. Table E-1 is valid only for

Models 6680A and 6681A - you must use the curves for the remaining models. The corresponding 10% overshoot

curves are shown in Figure E-1. As operation moves along the curves from left to right, the switch positions must be

changed as shown along the X-axis.

Table E-1.

Settings For CC Loop Compensation Switch (Models 6680A and 6681A Only)

Load Characteristic (L/R) 1Switch Setting

7654321

1 µH/3 mΩ0000000

215 µH/100 µΩ 1111111

30 µH/100 µΩ 0000001

100 µH/100 µΩ 1111110

150 µH/100 µΩ 0000010

600 µH/100 µΩ 1111100

1.2 mH/100 µΩ 0000100

4 mH/100 µΩ 1111000

10 mH/100 µΩ 0001000

40 mH/100µΩ 1110000

100 mH/100 µΩ 0010000

380 mH/100 µΩ 1100000

650 mH/100 µΩ 0100000

7 H/100 µΩ 1000000

1 "1" = switch closed; "0" = switch open. 2 Factory setting.

For example, examine Figure E-l for the Model 6680A/6681A. The chart shows that a load comprised of about