Datasheet

AD5560 Data Sheet
Rev. D | Page 32 of 68
Master in FV Mode, Slaves in Force Current (FI) Mode
The master device is placed into FV mode, and all slave devices
into force current (FI) mode. The measured current of the
master device (MASTER_OUT) is applied to the input of all
slave devices (SLAVE_IN), and the slaves act as followers. All
channels work to share the current equally among all devices
in the gang. Because the slaves force current, matching the
DUT paths is not so critical. Settings for DPS Register 2 are
master = 0x0200, slave = 0x0600. Clamps should be disabled in
the slave devices.
EXTMEASIL
MASTER DPS
EXTMEASIH1
SW5-a
FIN
DAC
MEASOUT
BUFFER
AND GAIN
I
SENSE
AMP
SENSE
SW5-a
SW16
SW5-b
SW6
MASTER OUT
EXTFORCE1
EXTFORCE2
SLAVE IN
EXTMEASIL
SLAVE DPS 1
EXTMEASIH1
SW5-a
FIN
DAC
MEASOUT
BUFFER
AND GAIN
I
SENSE
AMP
SENSE
SW5-a
SW16
SW5-b
SW6
MASTER OUT
EXTFORCE1
EXTFORCE2
SLAVE IN
EXTMEASIL
SLAVE DPS 2
EXTMEASIH1
SW5-a
FIN
DAC
MEASOUT
BUFFER
AND GAIN
I
SENSE
AMP
SENSE
SW5-a
SW16
SW5-b
SW6
MASTER OUT
EXTFORCE1
EXTFORCE2
SLAVE IN
DUT
DUTGND
×20
×20
×20
07779-008
R
SENSE
R
SENSE
R
SENSE
Figure 55. Simplified Block Diagram of Gang Mode,
Using an FV/FI Combination
The EXTFORCE1, EXTFORCE2, or ±25 mA ranges can be
used for the gang mode. Therefore, it is possible to gang devices
to get a high voltage/high current combination, or a low
voltage/high current combination.
For example, ganging five 25 V/25 mA devices using the 25 mA
range achieves a 25 V/625 mA range, whereas five 15 V/200 mA
devices using the EXTFORCE2 path can achieve a 15 V/1 A
range. Similarly, ganging four 3.5 V/1.2 A devices using the
EXTFORCE1 path results in a 3.5 V/4.8 A DPS.
IDEAL SEQUENCE FOR GANG MODE
Use the following steps to bring devices into and out of gang mode:
1. Choose the master device and force 0 V output, corres-
ponding to zero current.
2. Select slave DPS 1 and place it in slave mode (keep slaves in
high-Z mode via
SW-INH
or
HW_INH
until ready to gang).
3. Select to gang in either current or voltage mode.
4. Repeat Step 2 and Step 3 one at a time through the chain of
slaves.
5. Load the required voltage to the master device. The other
devices copy either voltage or current as programmed.
To remove devices from the gang, the master device should
be programmed to force 0 V out again. The procedure for
removing devices should be the reverse of Step 1 through Step 5.
Note that this may not always be possible in practice; therefore,
it is also possible to gang and ungang while driving a load. Just
ensure that the slave devices are in high-Z mode while confi-
guring them into the required range and gang setting.
Gang mode extends only to the ±25 mA range and the two high
current ranges, EXTFORCE1 and EXTFORCE2. Therefore, where
an accurate measurement is required at a low current, the user
should remove slaves from the gang to move to the appropriate
lower current range to make the measurement. Similarly, slaves
can be brought back into the gang if needed.
COMPENSATION FOR GANG MODE
When ganging, the slave devices should be set to the fastest
response.
When slaves are in FI mode, the AD5560 force amplifier over-
rides other compensation settings to enforce C
Fx
= 0, R
Z
= 0,
and g
mx
≤ 1. This is done internally to the force amplifier;
therefore, readback will not show that the signals inside the
force amplifier actually change.
SYSTEM FORCE/SENSE SWITCHES
System force/sense switches allow easy connection of a central
or system parametric measurement unit (PMU) for calibration
or additional measurement purposes.
The system device under test ground (SYS_DUTGND) switch
is shared with the GUARD/SYS_DUTGND pin (Pin 43). See
the DPS Register 2 in Table 19 for addressing details.