AD5520 Analog Devices, AD5520 Datasheet - Page 13

• Manufacturer Part Number: AD5520
• Description: Per Pin Parametric Measurement Unit/Source Measure Unit
• Manufacturer: Analog Devices

CIRCUIT OPERATION
Force Voltage
Most PMU measurements are performed while in force voltage
and measure current modes, for example, when the device is
used as a device power supply, or in continuity or leakage
testing. In the force voltage mode, the voltage at analog input
FIN is mapped directly to the voltage forced at the DUT.
When in force voltage and measure current modes, the maxi-
mum voltage applied to the input corresponds to the maximum
current outputs. Figure 4 shows the transfer function when forcing
a voltage.
Measure Current
Figure 5 shows a simplified diagram of the PMU when in force
voltage mode. The control loop consists of the force amplifier
with the voltage sense amplifier making up the feedback path.
Current flowing through the DUT is measured by sensing the
current flowing through a selectable sense resistor, which is in
series with the DUT. The current sense amplifier (Gain = 16)
generates a voltage at its output, which is proportional to the
current flowing through the DUT. This voltage is compared to
REV. A
Figure 4. Voltage Force Transfer Function
V
CLH
R
V
V
S
CLH
CLH
R
16
R
S
DUT
16
V
I
DUT
DUT
V
R
CLL
V
S
CLL
16
R
R
S
DUT
V
CLH
16
V
V
FIN
FIN
–13–
VFIN
the CLL and CLH levels to ensure the clamp voltages have not
been exceeded. Strobing CPCK and STB will provide information
about the voltage level with respect to the comparator levels,
CPH and CPL.
VFIN
Force Current
In the force current mode, the voltage at FIN is now converted
to a current through the following relationship:
Figure 6 shows a simplified diagram of the PMU when in
force current mode. The control loop consists of the force
amplifier with the current sense amplifier making up the feed-
back path. In this case, voltage at the DUT is sensed across
the voltage measure amplifier (Gain = 1) and presented at
the MEASVOUT output.
CONDITION
OUTPUT
Figure 5. Voltage Force, Measure Current Mode
Figure 6. Current Force, Voltage Measure Mode
VCLH
VCLH
CONDITION
V
V
OUTPUT
CLH
CLL
V
> I
< I
VCLL
VCLL
DUT
DUT
DUT
Force Current V
V
V
V
= V
V
FIN
VMEASIOUT
FIN
VMEASIOUT
VMEASVOUT
CLH
CLL
REFGNDI/V
FIN
CLH
REFGNDI/V
VMEASVOUT
R
R
CLL
V
V
I
DUT
CLH
S
S
CLL
=
> V
< V
16
16
V
R
FIN
DUT
DUT
S
V
V
CLH
CLL
=
V
V
I
V
DUT
< I
< I
CLH
CLL
DUT
DUT
DUT
FIN
=
< V
< V
= V
V
R
CLH
/
DUT
DUT
CLH
G = 16
G = 16
R
G = 1
R
R
S
G = 1
S
S
SENSE
16
16
V
V
I
DUT
CLH
CLL
V
=
V
> V
> V
AD5520
CLH
CLL
V
DUT
DUT
R
MEASIHx
CLL
MEASVH
MEASIHx
MEASVH
MEASVL
MEASVL
MEASIL
S
MEASIL
V
> I
> I
DUT
FOHx
FOHx
DUT
DUT
= V
CLL
R
R
S
S
R
R
16
16
R
R
S
DUT
S
DUT