User`s guide

3 - Installation

Output Compensation (High Mode/Low Mode)

High bandwidth performance and stability are achieved by using a software-switchable output

compensation circuit. This compensation circuit sets the remote sensing response of the dc source for the

capacitance of the cellular phones. The compensation function is set using either the front panel

TYPE:CAP command located in the Output menu (see chapter 5), or the OUTput:TYPE[:CAPacitance]

SCPI command as explained in chapter 8. The circuit covers the following capacitance ranges:

♦ Low Mode: 0 to 12,000 µF

♦ High Mode: 5 µF to 12,000 µF

The Agilent 66311B is shipped from the factory with the output compensation set to Low Mode. If you

do not know the input capacitance of the phone that you are testing, leave the input capacitance set to

Low Mode initially. This is because in Low Mode, the output of the dc source will be stable when testing

cellular phones that have virtually any input capacitance (from 0 µF to 12,000 µF). Low mode however,

has a slower transient response (see appendix A).

The High Mode output compensation setting provides faster transient response performance for most

phones. (Most phones have input capacitances greater than 5 µF.) In High Mode however, the operation

of the dc source may be momentarily unstable with phones that have input capacitances less than 5 µF.

If you are testing phones in High Mode and want to determine if the input capacitance of your phone is

less than 5 µF, perform the following test.

NOTE: It is important that this test is done with the dc source installed in the test system where it

will be used, since system stability is also dependent on wiring and the phone

impedance.

1. Connect the phone to the dc source and place it in standby mode.

2. Check the last two digits of the voltage reading on the front panel of the dc source.

3. If the last two digits are fluctuating, it is an indication that the phone capacitance may be less than

5 µF and the dc source is momentarily unstable.

4. Place the output compensation of the dc source in Low Mode.

5. If the last two digits of the voltage reading are now stable, your phone has an input capacitance less

than 5 µF.

Local Sensing

Remote sensing is preferred when connecting the output of the dc source to the load. However, you may

also connect the output to the load without remote sensing provided that you observe the following:

♦ Keep load leads as short as possible. Load leads cannot exceed 18 inches (per side) when local

sensing.

♦ Bundle or twist the leads tightly together to minimize inductance.

♦ Set the Sense switch on the back of the unit to Local by pushing it in.