Keithley 2657A-PM-200 User manual

Model 2657A-PM-200 Protection Module
Keithley Instruments, Inc. User's Guide
28775 Aurora Road
Cleveland, Ohio 44139
1-888-KEITHLEY
http://www.keithley.com
PA-1055 Rev. A / February 2012 1
Description
The Model 2657A-PM-200 Protection Module (PM) is a stand-alone module that protects certain lower-voltage
source-measure units (SMUs) that are part of a testing configuration from damage by voltage sources that are
greater than 220 V.
Figure 1: Model 2657A-PM-200
The protection module is designed for use with the following lower voltage SMUs:
•Model 2611A Single-Channel System SourceMeter Instrument
•Model 2612A Dual-Channel System SourceMeter Instrument
•Model 2635A Single-Channel System SourceMeter Instrument
•Model 2636A Dual-Channel System SourceMeter Instrument
•Model 4200-SCS Semiconductor Characterization System SMUs:
•Model 4200-SMU Medium Power Source-Measure Unit (with or without the Model 4200-PA Remote
PreAmp Option)
•Model 4210-SMU High Power Source-Measure Unit (with or without the Model 4200-PA Remote PreAmp
Option)
The protection module is intended for use in applications where a device breakdown or other potential failure could
connect the high-voltage output of the Model 2657A High Power System SourceMeter Instrument to a lower
voltage SMU.
The Model 2657A-PM-200 does not protect the Model 2601A Single-Channel System
SourceMeter Instrument or the Model 2602A Dual-Channel System SourceMeter Instrument. Do
not use the protection module with these source-measure instruments.

Model 2657A-PM-200 Protection Module
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To prevent damage to the Model 2657A-PM-200 in the case of device failure, the current from the
high-voltage source should be limited to 120 mA or less.
The Model 2657A-PM-200 protection module must be connected to protective earth (safety
ground) using the the supplied green-yellow ground cables (Model CA-568). Connection of
both ground cables to protective earth are necessary for safety.
Figure 2: Model 2657A-PM-200 grounding
The standard triaxial IN connectors are used for connection to the SMU. Maximum clamped voltage on the IN
connectors is 240 VDC. The high voltage triaxial connectors are used for connection to the device under test. Do
not exceed 3280 V on the OUT connectors.
•The center conductor of the LO,SL connectors is sense LO and the inner shield is LO. The outer shield (shell)
is chassis ground.
•The center conductor of the HI connectors is HI and the inner shield is guard. The outer shield (shell) is chassis
ground.
•The center conductor of the SH connectors is sense HI and the inner shield is guard. The outer shield (shell) is
chassis ground.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 3
Electrical characteristics
•Leakage: < 10 pA at 200 V typical
•DC current carrying capability: 1.5 A maximum in unclamped condition
•Pulsed current carrying capability: 10 A maximum at 1% duty cycle in unclamped condition
•Maximum protection active current: User must limit current to <120 mA in clamped condition (~230 V)
•Protection voltage:
•Minimum: 220 VDC
•Typical: 230 VDC
•Maximum: 240 VDC
•LO to GND voltage: 30 VDC typical
Mechanical dimensions
Figure 3: Model 2657A-PM-200 dimensions

Model 2657A-PM-200 Protection Module
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Connections using a Model 2611A or 2612A SMU
Required accessories:
•One Model 2600-TRIAX adapter per channel
•Two or three standard triaxial cables (either Model 7078-TRX or 4200-TRX) per channel
•Two or three high-voltage (HV) triaxial cables (Model CA-553 or CA-554) per channel
Connection summary
Use the connection drawing below to connect source-measure unit (SMU) channels of the Model 2611A or 2612A
to the Model 2657A-PM-200. For each channel, make sure to use the IN connectors of the the Model 2657A-PM-
200 for connection to the Model 2600-TRIAX and use the OUT connectors for connection to the device under test
(DUT).
The drawing shows connections for 4-wire sensing. For 2-wire applications, the SH (sense HI) connectors of the
Model 2657A-PM-200 are not used.
Connecting the Model 2600-TRIAX to the Model 2657A-PM-200 connects the LO terminal of the
Model 2611A or 2612A to protective earth (safety ground).
Do not convert triaxial cables to BNC cables. Using BNC cables removes protection from the Model
2611A or 2612A and may result in damage to the SMU. You must use triaxial cables to connect to the
lower-voltage SMU.
When using the 2657A-PM-200, HI and SH (sense HI) should be connected together at the device
under test. A potential difference between the two circuits in excess of 100 mV may result in
compromised measurements.
Large potential differences can be created when there is significant lead resistance and current
flowing in the HI lead. To minimize lead resistance, minimize the distance between the Model 2657A-
PM-200 and the device under test.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 5
Figure 4: Connections for a Model 2611A or 2612A

Model 2657A-PM-200 Protection Module
6 PA-1055 Rev. A / February 2012
Connections using a Model 2635A or 2636A SMU
Required accessories:
•Two or three standard triaxial cables (either Model 7078-TRX or 4200-TRX) per source-measure unit (SMU)
channel
•Two or three high-voltage (HV) triaxial cables (Model CA-553 or CA-554) per SMU channel
Connection summary
Use the connection drawing below to connect source-measure unit (SMU) channels of the Model 2635A or 2636A
to the Model 2657A-PM-200. For each channel, make sure to use the IN connectors of the Model 2657A-PM-200
for connection to the Model 2635A or 2636A and use the OUT connectors for connection to the device under test
(DUT).
The drawing shows connections for 4-wire sensing. For 2-wire applications, the SH (sense HI) connectors of the
Model 2657A-PM-200 are not used.
Do not convert triaxial cables to BNC cables. Using BNC cables removes protection from the Model
2635A or 2636A and may result in damage to the SMU. You must use triaxial cables to connect to the
lower-voltage SMU.
When using the 2657A-PM-200, HI and SH (sense HI) should be connected together at the device
under test. A potential difference between the two circuits in excess of 100 mV may result in
compromised measurements.
Large potential differences can be created when there is significant lead resistance and current
flowing in the HI lead. To minimize lead resistance, minimize the distance between the Model 2657A-
PM-200 and the device under test.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 7
Figure 5: Connections for a Model 2635A or 2636A

Model 2657A-PM-200 Protection Module
8 PA-1055 Rev. A / February 2012
Connections using a Model 4200-SCS SMU (with Model 4200-PA)
If ordered, a Model 4200-PA remote preamplifier (preamp) for a source-measure unit (SMU) is installed at the
factory when the Model 4200-SCS is ordered.
Required accessories to connect one Model 4200-SMU or 4210-SMU (with the Model 4200-PA):
•Two or three Model 4200-TRX cables
•Two or three high-voltage (HV) triaxial cables (Model CA-553 or CA-554)
Connection summary
Use the connection drawing below to connect a Model 4200-PA preamp and the GNDU (ground unit) to the Model
2657A-PM-200. Make sure to use the IN connectors of the Model 2657A-PM-200 for connection to the Model 4200-
SCS and use the OUT connectors for connection to the device under test (DUT).
The drawing shows connections for 4-wire sensing. For 2-wire applications, the SH (sense HI) connectors of the
Model 2657A-PM-200 are not used.
When using multiple SMUs that are installed in the Model 4200-SCS, each SMU needs its own
protection module. To achieve adequate voltage protection, connect the GNDU Sense terminal to the
LO,SL (LO and sense LO) connector of each protection module using triax tees (such as the Keithley
Model 237-TRX-T) and additional triaxial cables (Model 4200-TRX).
Connecting the Model 4200-SMU or 4210-SMU to the Model 2657A-PM-200 connects the LO
terminal of the SMU to protective earth (safety ground).
Do not convert triaxial cables to BNC cables. Using BNC cables removes protection from the Model
4200-SCS SMU and may result in damage to the SMU. You must use triaxial cables to connect to the
lower-voltage SMU.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 9
When using the Model 2657A-PM-200, HI and SH (sense HI) should be connected together at the
device under test. A potential difference between the two circuits in excess of 100 mV may result in
compromised measurements.
Large potential differences can be created when there is significant lead resistance and current
flowing in the HI lead. To minimize lead resistance, minimize the distance between the Model 2657A-
PM-200 and the device under test.
Figure 6: Connections for a Model 4200-SCS SMU (with preamp)

Model 2657A-PM-200 Protection Module
10 PA-1055 Rev. A / February 2012
Connections using a Model 4200-SCS SMU
Required accessories to connect one Model 4200-SMU or 4210-SMU (without the Model 4200-PA Remote
PreAmp):
•One Model 4200-TRX cable
•One or two Model 4200-MTRX cables
•Two or three high-voltage (HV) triaxial cables (Model CA-553 or CA-554)
Connection summary
Use the connection drawing below to connect a Model 4200-SMU or 4210-SMU and the GNDU (ground unit) to the
Model 2657A-PM-200. Make sure to use the IN connectors of the Model 2657A-PM-200 for connection to the
Model 4200-SCS and use the OUT connectors for connection to the device under test (DUT).
The drawing shows connections for 4-wire sensing. For 2-wire applications, the SH (sense HI) connectors of the
Model 2657A-PM-200 are not used.
When using multiple SMUs that are installed in the Model 4200-SCS, each SMU needs its own
protection module. To achieve adequate voltage protection, connect the GNDU Sense terminal to the
LO,SL (LO and sense LO) connector of each protection module using triax tees (such as the Keithley
Model 237-TRX-T) and additional triaxial cables (Model 4200-TRX).
Connecting the Model 4200-SMU or 4210-SMU to the Model 2657A-PM-200 connects the LO
terminal of the SMU to protective earth (safety ground).
When using the 2657A-PM-200, HI and SH (sense HI) should be connected together at the device
under test. A potential difference between the two circuits in excess of 100 mV may result in
compromised measurements.
Large potential differences can be created when there is significant lead resistance and current
flowing in the HI lead.To minimize lead resistance, minimize the distance between the Model 2657A-
PM-200 and the device under test.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 11
Figure 7: Connections for a Model 4200-SCS SMU

Model 2657A-PM-200 Protection Module
12 PA-1055 Rev. A / February 2012
Verify Model 2657A-PM-200 operation
A simplified block diagram of the Model 2657A-PM-200 is shown below.
Figure 8: Simplified diagram of the Model 2657A-PM-200
The voltage protection device is connected between Guard and LO. Low-leakage diodes are used to connect both
HI and Sense HI to the Guard terminal. This enables the protection module to protect a SMU connected to the IN
terminals from overvoltage.
The Zener diodes between LO and chassis and Sense LO and chassis limit the maximum voltage between LO and
chassis ground to 30 V to 40 V.
Use the following procedures to verify that the Model 2657A-PM-200 is operating properly.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 13
Verify diodes between HI / sense HI and guard
A Keithley SourceMeter instrument capable of sourcing 10 mA at 10 V is required for verification procedures A
and B.
Verification procedure A
Verify the operation of the diodes between Sense HI and Guard of the Model 2657A-PM-200:
1. As shown in the connection drawing below, connect the source-measure unit (SMU) to the SH triaxial
connector of the protection module:
a. Connect the SMU Force HI terminal to the center conductor of the SH IN triaxial connector of the Model
2657A-PM-200.
b. Connect the SMU Force LO terminal to the inner shield of the SH IN triaxial connector of the Model
2657A-PM-200.
Figure 9: Connections for verification procedure A
2. Configure the SMU to source current and measure voltage.
3. Program the current source level to 10 mA.
4. Set the voltage limit to 10 V.
5. Turn on the SMU output.
6. Verify that the voltage measured by the SMU is between 0.6 V and 1.0 V.
7. Program the SMU current source level to -10 mA.
8. Verify that the voltage measured is between -0.6 V and -1.0 V.

Model 2657A-PM-200 Protection Module
14 PA-1055 Rev. A / February 2012
Verification procedure B
Verify the operation of the diodes between HI and Guard of the Model 2657A-PM-200:
1. As shown in the connection drawing below, connect the source-measure unit (SMU) to the HI triaxial connector
of the protection module:
a. Connect the SMU Force HI terminal to the center conductor of the HI OUT triaxial connector of the
Model 2657A-PM-200.
b. Connect the SMU Force LO terminal to the inner shield of the HI OUT triaxial connector of the Model
2657A-PM-200.
Figure 10: Connections for verification procedure B
2. Configure the SMU to source current and measure voltage.
3. Program the current source level to 10 mA.
4. Set the voltage limit to 10 V.
5. Turn on the SMU output.
6. Verify that the voltage measured is between 0.6 V and 1.0 V.
7. Program the current source level to -10 mA.
8. Verify that the voltage measured is between -0.6 V and -1.0 V.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 15
Verify diodes between LO / sense LO and chassis
A Keithley SourceMeter instrument capable of sourcing 10 mA at 50 V is required for verification procedures C
and D.
A safety shield must be used whenever hazardous voltages (>30 V RMS, 42 V peak) will be
present in the test circuit. To prevent electrical shock that could cause injury or death, never
use a Keithley SourceMeter®instrument in a test circuit that may contain hazardous voltages
without a properly installed and configured safety shield. The following procedures show the
use of a metal safety shield. Connect the enclosure of the metal test fixture to protective earth
(safety ground).
If using a nonconductive test fixture, it must be rated to double the maximum capability of the
test equipment in the system and the two green-yellow ground cables for the Model 2657A-
PM-200 must be connected to protective earth (safety ground). Failure to attach the ground
wires to a known protective earth may result in electric shock.
Verification procedure C
Verify the operation of the diodes between Sense LO and the chassis of the Model 2657A-PM-200:
1. As shown in the connection drawing below, connect the source-measure unit (SMU) to the SL triaxial connector
of the protection module:
a. Connect the SMU force HI terminal to the center conductor of the SL OUT triaxial connector of the
Model 2657A-PM-200.
b. Connect the SMU force LO terminal to the outer shield (chassis) of the SL OUT triaxial connector of the
Model 2657A-PM-200. The chassis is available at the outer shield of any of the triaxial connectors on
the Model 2657A-PM-200.
Figure 11: Connections for verification procedure C

Model 2657A-PM-200 Protection Module
16 PA-1055 Rev. A / February 2012
2. Configure the SMU to source current and measure voltage.
3. Program the current source level to 10 mA.
4. Set the voltage limit to 50 V.
5. Turn on the SMU output.
6. Verify that the voltage measured is between 30 V and 40 V.
7. Program the current source level of the SMU to -10 mA.
8. Verify that the voltage measured is between -30 V and -40 V.
Verification procedure D
Verify the operation of the diodes between LO and the chassis of the Model 2657A-PM-200:
1. As shown below, connect the SMU to the LO,SL triaxial connector of the protection module:
a. Connect the SMU force HI terminal to the inner shield of the LO,SL IN triaxial connector of the Model
2657A-PM-200.
b. Connect the SMU force LO terminal to the outer shield (chassis) of the LO,SL IN triaxial connector of
the Model 2657A-PM-200. The chassis is available at the outer shield of any of the triaxial connectors
on the Model 2657A-PM-200.
Figure 12: Connections for verification procedure D
2. Configure the SMU to source current and measure voltage.
3. Program the current source level to 10 mA.
4. Set the voltage limit to 50 V.
5. Turn on the output.
6. Verify that the voltage measured is between 30 V and 40 V.
7. Program the current source level of the SMU to -10 mA.
8. Verify that the voltage measured is between -30 V and -40 V.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 17
Verify voltage protection device between Guard and Force LO
A Keithley SourceMeter instrument capable of sourcing 20 mA at 300 V is required for verfication procedures E
and F. The Model 2657A High Power System SourceMeter Instrument or Model 2410 High Voltage
SourceMeter Instrument is recommended. An oscilloscope capable of measuring up to 300 V is also
recommended.
A safety shield must be used whenever hazardous voltages (>30 V RMS, 42 V peak) will be
present in the test circuit. To prevent electrical shock that could cause injury or death, never
use a Keithley SourceMeter® instrument in a test circuit that may contain hazardous voltages
without a properly installed and configured safety shield. The following procedures show the
use of a metal safety shield. Connect the enclosure of the metal test fixture to protective earth
(safety ground).
If using a nonconductive test fixture, it must be rated to double the maximum capability of the
test equipment in the system and the two green-yellow ground cables for the Model 2657A-
PM-200 must be connected to protective earth (safety ground). Failure to attach the ground
wires to a known protective earth may result in electric shock.
Not shown in the simplified block diagram are redundant voltage protection devices between the inner shields
(guard) of the HI and SH (sense HI) terminals of the Model 2657A-PM-200. Verification procedures E and F checks
both of these devices.
Verification procedure E
Verify proper operation of the protection device between the inner shields of the Sense HI (SH) and LO terminals of
the Model 2657A-PM-200:
1. As shown in the connection drawing below, connect the high voltage source-measure unit (HV SMU) to the SH
and SL triaxial connectors of the protection module:
a. Connect the SMU Force HI terminal to the inner shield of the SH OUT triaxial connector of the Model
2657A-PM-200.
b. Connect the SMU Force LO terminal to the inner shield of the SL OUT triaxial connector of the Model
2657A-PM-200.

Model 2657A-PM-200 Protection Module
18 PA-1055 Rev. A / February 2012
Figure 13: Connections for verification procedure E
2. Configure the HV SMU to source current and measure voltage.
3. Program the current source level to 20 mA.
4. Program the voltage limit to 220 V.
5. Turn on the HV SMU output.
6. Verify that the voltage measured is 220 V.
7. Program the current source level to -20 mA.
8. Verify that the voltage measured is -220 V.
9. Turn off the HV SMU output.
10. Connect the scope across the output terminals of the HV SMU.
11. Configure the HV SMU to source voltage.
12. Program the voltage source level to +300 V.
13. Turn on the HV SMU output and trigger the scope.
14. Verify that the voltage waveform on the scope has a ramped waveform. The voltage should ramp up to at
least 150 V and then clamp to less than 50 V.
15. Turn off the HV SMU output.
16. Program the voltage source level to -300 V.
17. Turn on the HV SMU output.
18. Verify that the voltage waveform on the scope has a ramped waveform. The voltage should ramp down to
at least -150 V and then clamp to less than -50 V.

Model 2657A-PM-200 Protection Module
PA-1055 Rev. A / February 2012 19
Verification procedure F
Verify proper operation of the protection device between the inner shields of the HI and LO terminals of the Model
2657A-PM-200:
1. As shown in the connection drawing below, connect the high voltage source-measure unit (HV SMU) to the HI
and LO,SL triaxial connectors of the protection module:
a. Connect the SMU Force HI terminal to the inner shield of the HI OUT triaxial connector of the Model
2657A-PM-200.
b. Connect the SMU Force LO terminal to the inner shield of the LO,SL OUT triaxial connector of the
Model 2657A-PM-200.
Figure 14: Connections for verification procedure F
2. Configure the HV SMU to source current and measure voltage.
3. Program the current source level to 20 mA.
4. Program the voltage limit to 220 V.
5. Turn on the HV SMU output.
6. Verify that the voltage measured is 220 V.
7. Program the current source level to -20 mA.
8. Verify that the voltage measured is -220 V.
9. Turn off the HV SMU output.
10. Connect the scope across the output terminals of the HV SMU.
11. Configure the HV SMU to source voltage.
12. Program the voltage source level to +300 V.

Model 2657A-PM-200 Protection Module
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13. Turn on the HV SMU output and trigger the scope.
14. Verify that the voltage waveform on the scope has a ramped waveform. The voltage should ramp up to at
least 150 V and then clamp to less than 50 V.
15. Turn off the HV SMU output.
16. Program the voltage source level to -300 V.
17. Turn on the HV SMU output.
18. Verify that the voltage waveform on the scope has a ramped waveform. The voltage should ramp down to
at least -150 V and then clamp to less than -50 V.