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

User Connections

Auto-Parallel Programming. Program only the first ("master") supply in the series; the "slave" supplies automatically

track the master’s output. However, the voltage and OVP settings of the slave supplies must be set higher than the operating

voltage of the master supply. This ensures that the slave supplies will operate in CC mode. Functions such as status, voltage

readback, and current readback can still be read back individually for each supply.

If a "slave" supply experiences a desired shutdown condition (such as overtemperature or overcurrent), it will not

automatically shut down all other supplies. You must first enable remote inhibit (RI) and discrete fault indicator (DFI)

operation. See "Fault/Inhibit Operation" in Appendix D for wiring information and "Questionable Status Group" in

Chapter 4 of the Programming Guide for programming information.

Follow the following operating precautions if you are connecting three of these models in auto-parallel.

You must use caution when connecting three Series 664xA or 665xA power supplies for auto-parallel operation. That is

because of the OVP crowbar circuits within these supplies. If the OVP circuit of the second "slave" trips, its crowbar circuit

will draw current from the other two supplies. Although some models can withstand this current, the higher-current models

in each series (particularly the Agilent 6651A) may be damaged in this situation. Use any of the following operating

techniques to avoid possible problems.

1. Program Slave 2 OVP to the Maximum Level

The following technique minimizes the chance that the slave 2 OVP circuit will trip.

a. Program the OVP level of the master and of slave 1 to the desired protection level (below the maximum level

specified in Table 1-2).

b. Program the OV protection level of slave 2 to its maximum value.

2. Enable OCP on the Master

You can do this if the combination of all three supplies is being used in the CV mode and the CC mode is only being used as

a current limit. Enable OCP on the master supply. If the OVP on either slave trips it will drive the master into CC mode,

thereby tripping its OCP. This will shut down all three supplies. This technique will work unless the system is programmed

for very low (0.5 to 1.5) output voltages.

3. Insert Protection Diodes

If you connect the slave 2 supply to the load through a series diode (see Figure 4-3e), its OVP circuit will not draw current

from other supplies. Be certain to increase the programmed CV level of slave 2 by at least 0.7 V to compensate for the

voltage drop in the diode.

Figure 4-3e. Using Series Diodes with Series 664xA & 665xA Auto-Parallel Operation

Note Removing or disabling the power supply OVP crowbar SCR is another possibility. For further

information, contact a Agilent Service Engineer through your local Agilent Sales and Support Offices.