Keithley Instruments
Model 4225-RPM
PA-1086 Rev. B March 2023
1
28775 Aurora Road
Cleveland, Ohio 44139
1-800-833-9200
tek.com/keithley
Remote Pulse Module Instructions
Overview
The Keithley Instruments Model 4225-RPM Remote Preamplifier/Switch Module (RPM) is a remote amplifier
and automatic switch. It is a multiplexer switch that automatically switches between precision dc
source-measure units (SMUs), C-V, and the ultra-fast pulsed I-V ins tru ments .
The RPM also extends the low current measurement capability of the 4225-PMU Ultra-Fast Pulsed I-V
Instrument Module. This is especially important for devices like diodes or transistors that have I-V curves that
extend over several decades of current. The autorange feature of the 4225-RPM enables automatic range
selection while a pulsed I-V sweep is in progress. This feature provides optimal current measurement while the
device signal transitions through different current levels. The RPM adds the following current ranges to the
4225-PMU: 100 nA, 1 μA, 10 μA, 100 μA, 1 mA, and 10 mA.
Figure 1: 4225-RPM
*PPA-1086B*
Model 4225-RPM Remote Pulse Module Instructions
1
RPM interconnect cable, 2.4 m (8 ft)
CA-547-2.4
1 2 Triaxial to BNC adapter (guard removed)
CS-712
1 3 BNC-SMA female adapter
CS-1247
1 4 SMA to SMA cable, 20 cm (8 in.)
CA-452
1 5 Protective cap
CAP-47
2 6 Triaxial caps (for shielding, not shorting)
CA-31
4
Not shown
Support bracket
4200-322
1
Not shown
Captive panel screw (for support bracket)
FA-243-2
1
Not shown
Allen socket head capscrew, #4-40 x 5/16"
4-40x5/16SOHBLK
1
Not shown
Hex wrench, 3/32 in.
TL-32
1
Included accessor ies
The following cables, adapters, and accessories are included in the remote pulse module kit.
Figure 2: 4225-RPM included accessories
Item Description Keithley part number Quantity
Available cabl e kits
Model 4210-MMPC High Performance Triaxial Cable Kits (ordered separately) simplify RPM connections to a
prober, simplifying switching between dc I-V, C-V, and pulsed I-V testing configurations. These optional kits are
customized for specific probers. One kit is required for each pin of the device under test (DUT).
For additional information, refer to the 4200A-SCS Parameter Analyzer Datasheet, available from
tek.com/keithley
.
2 PA-1086 Rev. B March 2023
Model 4225-RPM Remote Pulse Module Instructions
Indicators
When the RPM is operational in a 4200A-SCS system, an LED on top of the RPM illuminates. The color of the
LED indicates which instrument is connected to the DUT during a test. Use the color codes in the following
figure to determine which instrument is connected. Note that the instrument indicator does not show that a test
is running or that the output of an instrument is active. To determine if a test is running, check the status
in Clarius.
Figure 3: Instrument indicator
Switching and connections
The 4225-RPM allows for automatic switching between dc I-V, C-V, and pulsed I-V measurements when
executed in ITM tests. The following topics describe typical connections for these measurements.
When properly installed, you can perform different electrical measurements on the device without having to
disconnect and reconnect cabling for each test. Optional multi-measurement performance cable kits
(Model 4210-MMPC) are available to connect the 4200A-SCS to a prober manipulator. In addition to eliminating
the need for recabling, these kits help maximize signal fidelity by eliminating the measurement errors that often
result from cabling errors.
Connecting the RPM to the PMU
Turn off the system and disconnect the power cord before connecting or disconnecting the
RPM to or from the PMU. Failure to do so may result in RPM or PMU damage, possibly
voiding the warranty.
The RPM is matched to a PMU card and channel. Make sure to connect the RPM only to that PMU
card and channel. Labels on top of the RPM indicate the specific connection channel and PMU. For
example, "PMU1-2" indicates PMU1, channel 2.
PA-1086 Rev. B March 2023 3
Model 4225-RPM Remote Pulse Module Instructions
With system power off, use the supplied RPM cable to connect a 4225-RPM to the matching RPM channel of
the 4225-PMU, as shown in the following figure.
Figure 4: 4225-PMU connection to an RPM
With an RPM installed, never make connections directly to any of the SMA connectors (CH1
and CH2) on the PMU. This may result in damage to the PMU or DUT. It may als o produce
corrupt data.
After connecting or removing an RPM, always perform the procedure “Update the RPM
configuration” in Model 4200A-SC S Set up and Ma inte nanc e to ensure that KCon accurately
represents the present 4200A-SCS hardware configuration.
Mounting the RPM
When mounting the 4225-RPM, make sure that there is a minimum of 5 cm (2 in.) of space
between multiple RPM base assemblies. Spacing multiple 4225-RPM or 4200-PA instruments
closer than 5 cm (2 in.) from the 4200-MAG-BASE can cause the internal relays
to malfunction.
4 PA-1086 Rev. B March 2023
Model 4225-RPM Remote Pulse Module Instructions
Connections to a 4-terminal device
The following illustrates the connection to a 4-terminal device using the cabling and adapters that are included
with either RPM or the 4225-PMU.
Figure 5: RPM output connection to 4-terminal device
PA-1086 Rev. B March 2023 5
Model 4225-RPM Remote Pulse Module Instructions
Typical 2-terminal connections
The following figure illustrates the connections to 2-termin al dev ices using the opt ion al MM PC cab ling. This
figure shows two RPMs and two 4210-MMPC cable kits.
Figure 6: Typical diode connections
6 PA-1086 Rev. B March 2023
Model 4225-RPM Remote Pulse Module Instructions
Typical 4-terminal device connections
The following figure shows RPM connections to a 4-terminal device using three optional MMPC cable kits.
Figure 7: Typical MOSFET connection
Load-line effect
The load-line effect causes voltage across the DUT to be lower than the programmed source voltage. The
output resistance of a pulsing instrument causes this effect. This resistance causes a reduction in output
voltage at the test device when current flows. By design, pulse instruments such as the 4225-PMU typically
have 50 Ω of resistance when placed in series with the output. The resistance causes a voltage drop
proportional to the current flow and is called the load-line effect.
The following figure shows the result of the load-line effect when measuring standard transistor V
with the 4225-PMU on its 200 mA range. Even though the user specified a source voltage of 6 V with a current
of about 25 mA (the blue curve at around 25E−3, I
), about 4.8 V is applied to the DUT, while about 1.2 V
DS
(marked A) is dropped inside the 4225-PMU and is not applied to the DUT. The difference between the actual
voltage sourced at the load line and the sourced voltage is caused by the load-line effect. The amount shown at
A is more than 1 V of loss. Increasing the amperage of the curve increases this effect. The amount shown at B
is more than 2 V of loss.
DS-IDS
curves
PA-1086 Rev. B March 2023 7
Model 4225-RPM Remote Pulse Module Instructions
The load line is defined by V
and the resistance of the pulse instrument. The output resistance of the
SRC
4225-PMU entirely determines its slope. The 4225-PMU programmed source voltage determines its horizontal
position. Larger voltages shift the line to the right. Smaller voltages shift it to the left. For a given programmed
source voltage, the actual DUT voltage cannot go beyond this line.
The slope is defined by the equation:
slope = −1/R
SRC
Figure 8: VDS-IDS curves for a MOSFET showing the load-line effect at high currents
The 4225-RPM has resistance in series with its output (typically between 20 Ω and 50 Ω). It also exhibits the
load-line effect.
8 PA-1086 Rev. B March 2023
Safety precaut ions
The following safety precautio ns should be observed before using this product and any associa t ed inst rum enta tion. Although
some instruments and accessories would normally be used with nonhazardous voltages, there are situations where hazardous
conditions may be present.
This product is intended for use by personnel who recognize shock hazards and are familiar with the safety precautions required
to avoid possible injury. Read and follow all installation, operation, and maintenance information carefully before using the
product. Refer to the user documentation for complete product specifications.
If the product is used in a manner not specified, the protection provided by the product warranty may be impaired.
The types of product users are:
Responsible body is the individual or group responsible for the use and maintenance of equipment, for ensuring that the
equipment is operated within its specifications and operating limits, and for ensuring that operators are adequately trained.
Operators use the product for its intended function. They must be trained in electrical safety procedures and proper use of the
instrument. They must be protected from electric shock and contact with hazardous live circuits.
Maintenance personnel perform routine procedures on the product to keep it operating properly, for example, setting the line
voltage or replacing consumable materials. Maintenance procedures are described in the user documentation. The procedures
explicitly state if the operator may perform them. Otherwise, they should be performed only by service personnel.
Service personnel are trained to work on live circuits, perform safe installations, and repair products. Only properly trained
service personnel may perform installation and service procedures.
Keithley products are designed for use with electrical signals that are measurement, control, and data I/O connections, with low
transient overvoltages, and must not be directly connected to mains voltage or to voltage sources with high transient
overvoltages. Measurement Category II (as referenced in IEC 60664) connections require protection for high transient
overvoltages often associated with local AC mains connections. Certain Keithley measuring instruments may be connected to
mains. These instruments will be marked as category II or higher.
Unless explicitly allowed in the specifications, operating manual, and instrument labels, do not connect any instrument to mains.
Exercise extreme caution when a shock hazard is present. Lethal voltage may be present on cable connector jacks or test
fixtures. The American National Standards Institute (ANSI) states that a shock hazard exists when voltage levels greater than
30 V RMS, 42.4 V peak, or 60 VDC are present. A good safety practice is to expect that hazardous voltage is present in any
unknown circuit before measuring.
Operators of this product must be protected from electric shock at all times. The responsible body must ensure that operators
are prevented access and/or insulated from every connection point. In some cases, connections must be exposed to potential
human contact. Product operators in these circumstances must be trained to protect themselves from the risk of electric shock. If
the circuit is capable of operating at or above 1000 V, no conductive part of the circuit may be exposed.
Do not connect switching cards directly to unlimited power circuits. They are intended to be used with impedance-limited
sources. NEVER connect switching cards directly to AC mains. When connecting sources to switching cards, inst all prot e ctiv e
devices to limit fault current and voltage to the card.
Before operating an instrument, ensure that the line cord is connected to a properly-grounded power receptacle. Inspect the
connecting cables, test leads, and jumpers for possible wear, cracks, or breaks before each use.
When installing equipment where access to the main power cord is restricted, such as rack mounting, a separate main input
power disconnect device must be provided in close proximity to the equipment and within easy reach of the operator.
For maximum safety, do not touch the product, test cables, or any other instruments while power is applied to the circuit under
test. ALWAYS remove power from the entire test system and discharge any capacitors before connecting or disconnecting
cables or jumpers, installing or removing switching cards, or making internal changes, such as installing or removing jumpers.
Do not touch any object that could provide a current path to the common side of the circuit under test or power line (earth)
ground. Always make measurements with dry hands while standing on a dry, insulated surface capable of withstanding the
voltage being measured.
PA-1086 Rev. B March 2023 9
For safety, instruments and accessories must be used in accordance with the operating instructions. If the instruments or
accessories are used in a manner not specified in the operating instructions, the protection provided by the equipment may be
impaired.
Do not exceed the maximum signal levels of the instruments and accessories. Maximum signal levels are defined in the
specifications and operating information and shown on the instrument panels, test fixture panels, and switching cards.
When fuses are used in a product, replace with the same type and rating for continued protection against fire hazard.
Chassis connect io n s mu st only be used as shield connections for measuring circuits, NOT as protective earth (safety ground)
connections.
If you are using a test fixture, keep the lid closed while power is applied to the device under test. Safe operation requires the use
of a lid interlock.
If a
The symbol on an instrument means caution, risk of hazard. The user must refer to the operating instructions located in the
user documentation in all cases where the symbol is mark ed on the instr u ment .
The
contact with these voltages.
The
The symbol indicates a connection terminal to the equipment frame.
If this symbol is on a product, it indicates that mercury is present in the display lamp. Please note that the lamp must be
properly disposed of according to federal, state, and local laws.
The WARNING heading in the user documentation explains hazards that might result in personal injury or death. Always read
the associated information very carefully before performing the indicated procedure.
The CAUTION heading in the user documentation explains h azard s that coul d dama ge the instrument. Such damage may
invalidate the warranty.
The CAUTION heading with the
injury or damage the instrument. Always read the associated information very carefully before performing the indicated
procedure. Damage to the instrument may invalidate the warranty.
Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and all test cables.
screw is present, connect it to protective earth (safety ground) using the wire recommended in the user documentation.
symbol on an instrument means warning, risk of electric shock. Use standard safety precautions to avoid personal
symbol on an instrum ent shows that the surface may be hot. Avoid personal contact to prevent burns.
symbol in the user documentation explains hazards that could result in moderate or minor
To maintain protection from electric shock and fire, replacement components in mains circuits — including the pow er
transformer, test leads, and input jacks — must be purchased from Keithley. Standard fuses with applicable national safety
approvals may be used if the rating and type are the same. The detachable mains power cord provided with the instrument may
only be replaced with a similarly rated power cord. Other components that are not safety-related may be purchased from other
suppliers as long as they are equivalent to the original component (note that selected parts should be purchased only through
Keithley to maintain accuracy and functionality of the product). If you are unsure about the applicability of a replacement
component, call a Keithley office for information.
Unless otherwise noted in product-specific literature, Keithley instruments are designed to operate indoors only, in the following
environment: Altitude at or below 2,000 m (6,562 ft); temperature 0 °C to 50 °C (32 °F to 122 °F); and pol luti on degree 1 or 2.
To clean an instrument, use a cloth dampened with deionized water or mild, water-based cleaner. Clean the exterior of the
instrument only. Do not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument. Products that
consist of a circuit board with no case or chassis (e.g., a data acquisition board for installation into a computer) should never
require cleaning if handled according to instructions. If the board becomes contaminated and operation is affected, the board
should be returned to the factory for proper cleaning/servicing.
Safety precaution revision as of June 2018.
10 PA-1086 Rev. B March 2023
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