Section 14: TSP command reference
2470 High Voltage SourceMeter Instrument Reference Manual
14-108
2470-901-01 Rev. A /
May
2019
Details
In some tests, the limited bandwidth of the SMU may cause current to exceed either the programmed
current or the limit current value. To prevent this from occurring, you can turn on the breakdown
protection function. This adds a 500
Ω resistor in series with the SMU force lead. This resistor limits
,
at a wide bandwidth, the breakdown current to a maximum value of V
OUTPUT
/500.
When the breakdown protection is set for AUTO operation, the resistor is in place for the 200 V and
1000 V ranges and current ranges less than or equal to the 10 mA range. Above the 10 mA range or
on lower voltage ranges, the breakdown protection resistor is automatically taken out of series with
the SMU force lead.
An example of when breakdown protection is appropriate is when you are testing components to
specify the DUT breakdown voltage. One method is to test the component at the specified breakdown
voltage and determine if the leakage current has exceeded a threshold level. For example, if you are
testing a 1000 V rated MOSFET, you can short the gate to the source and apply 1050 V from the
drain to the source while measuring the actual drain current. Testing at 1050 V instead of 1000 V
provides some assurance that the component both meets and exceeds the breakdown requirement
by some user-specified margin. In this test, if the breakdown protection is off, you may find that at the
exact moment of component breakdown, the current may exceed the limit current value. With the
breakdown function on, the peak current is limited to V
OUTPUT
/500.
A more comprehensive method of testing components to specify the DUT breakdown voltage is to
measure the actual component breakdown voltage. To do this on a 1000 V rated MOSFET, you need
to switch the sourcing method to current and the limit voltage to 1100 V (higher than the highest
expected breakdown voltage). Sourcing the value of the breakdown current permits the SMU to
measure the actual breakdown voltage of the component, which occurs precisely when the SMU
reaches the programmed source current. When this operating point is reached, a voltage
measurement records the actual breakdown voltage of the component, after which the small source
current used to find this breakdown voltage can be reduced to zero while waiting for the next
component to test. The entire test should be done quickly with the lowest possible breakdown current
to limit device self-heating. When performing this test, if the breakdown protection is off, you may find
that at the exact moment of component breakdown, the current may exceed the limit current
value. With the breakdown function on, the peak current is limited to V
OUTPUT
/500.
Example
selection = display.input.option("Breakdown Control", "Auto", "Always On", "Always
Off")
if selection ~= nil then
if selection == display.BUTTON_OPTION1 then
smu.breakdownprotection = smu.BREAKDOWN_AUTO
elseif selection == display.BUTTON_OPTION2 then
smu.breakdownprotection = smu.BREAKDOWN_ON
elseif selection == display.BUTTON_OPTION3 then
smu.breakdownprotection = smu.BREAKDOWN_OFF
end
end
Display a prompt that allows the user to select which type of breakdown protection to set.
Also see
None
