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

Using Agilent 668xA Series Power Supplies in Autoparallel 129

Using Agilent 668xA Series Power Supplies in Autoparallel

This information is supplementary to the information on page 80.

A maximum of three Agilent 668xA series power supplies having the same model number, may be configured for

autoparallel operation. The Agilent 668xA power supplies were designed with an external programming offset so that the

master unit will output current before the slave units do. Therefore, slave supplies will always sink current when low output

current values are desired.

Autoparallel Procedure

1. Connect the Agilent 668xA power supplies with the Im terminal from the master connected to the +Ip terminal of each

slave. Connect the ÏP terminal of the master to the -Ip terminal of each slave (see Figure 4-5e on page 81).

2. Each load lead should be of the same wire gauge and length.

3. Turn on all power supplies.

4. Program each slave supply for zero (0) output current either by pressing [CURRENT ] [0] [ENTER] from the front panel

keypad or sending the command "CURR:LEV 0" via the GPIB (see notes 2 and 3 on the follwing page).

5. Program each slave’s output voltage at least 2 volts higher than the output voltage that the master supply will be

programmed to.

6. Program the master supply’s output current for a value slightly greater than one-half of the total desired output current if

there is one slave supply, or one-third of the total desired output current if there are two slave supplies.

7. Enable all power supplies by pressing the [Output On/Off ] key.

8. Increase the master supply’s output voltage. At low output currents, the master unit will be supplying all of the load

current and the slave supplies will be sinking current, which is normal. At maximum output current each supply will be

delivering an equal amount of output current. When operating at less than maximum current, it is normal to have unequal

current sharing between the master and slave supplies. Current sharing among the supplies only becomes equal at

maximum output current (see Figure F-1 ).

9. For remote sensing, connect only the master supply’s +S and -S lines. Slave supplies should be connected for local

sensing at the rear of their respective output terminals.

Note 1 The current division between the master and slaves can be determined as follows:

Iout=Im [ 1 +Ns ( 1 +0.127V/5V)] - Ns Ifs (0.127V/5V)

The amount of current the master unit must output before the slave units will output current can be determined as follows:

Ns * Ifs (0.127V/5V)

where Im = master current

Ns = number of slaves

Ifs = full scale current

Example: 1 master unit, 2 slave units, Agilent Models 6680A (5V, 875A)

Iout = Im ( 3.0508 ) - 44.4A