Model 2657A-LIM-3 LO Interconnect Module
PA-1063 Rev. A / March 2012
5
Safety interlock and test enclosure for DUT
The test system uses the Model 2657A High Power System SourceMeter
Instrument, which requires the use of
the safety interlock. A properly configured safety interlock disables power from the source-measure units (SMUs)
when the lid or door of a test enclosure for the device under test (DUT) is opened. Power is enabled when the lid or
door is closed.
A user-supplied switch is required for the safety interlock. The normally-open switch must be used on a test fixture,
on the enclosure of a semiconductor prober or device handler, or on the doors of a test-equipment rack.
The switch must be installed as follows:
•
The switch must open when the lid or door of the test enclosure is opened.
•
The switch must close when the lid or door of the test enclosure is closed.
The following drawing shows the supplied interlock cable that is used to connect the switch to the Model
2657A-LIM-3 INTERLOCK OUT connector.
Figure 7: Supplied interlock cable
The interlocks of the SMUs in the test system must also be connected to the Model 2657A-LIM-3. The connection
drawings provided in the following topics show how to connect the interlocks to the Model 2657A-LIM-3.
The interlock circuit is powered from from the connected SMUs. Power is routed through the Model 2657-LIM-3 to
the the closed external switch to activate the interlock. The Interlock voltage from the Model 4200-SCS is +12 V
and the voltage from the other SMUs is +5 V.
Connections to device under test
The SMU terminals for connection to the device under test (DUT) are found at the following locations in the test
system:
•
The HI and SENSE HI terminals for the Model 2611A, 2612A, 2635A, 2636A, and 4200-SCS SMUs are
accessed at the Model 2657A-PM-200.
•
The HI and SENSE HI terminals for the Model 2657A are accessed at its rear panel.
•
The common LO and SENSE LO terminals for the SMUs are accessed at the Model 2657A-LIM-3.
Internal to the Model 2657A-LIM-3, the SENSE LO terminal is connected to the LO terminal with a 100 k
Ω
resistor.
This resistor permits access to LO and SENSE LO through a single connector (OUTPUT LO of the Model 2657A-
LIM-3). This can be useful in applications where 4-wire sense is desired but it may be troublesome to add a fourth
connection. Four-wire sense can be essentially achieved with three connections. Note that there may be some
voltage error due to lead resistance from the OUTPUT LO connector of the Model 2657A-LIM-3 to the DUT.
The connection drawings provided in the following topics show the cables required to connect the SMUs to the
DUT. The drawings show connections for 4-wire sensing. For 2-wire applications, the SH (sense HI) connectors of
the Model 2657A-PM-200 and the SENSE HI connector of the Model 2657A are not used.
