The Chroma 52400 series is a PXI based SMU (Source Measurement Unit) card designed for highly accurate source or load simulation with precision voltage and current easurements.
The SMU combines four-quadrant operation with precision and high speed measurement. This makes the SMU an ideal instrument in many parametric test applications ranging from ICs, two-leaded components such as sensors, LEDs, laser diodes, transistors, to solar cells, batteries and many other electronic devices.
The 52400 series features: 16 selectable control bandwidths to ensure high speed output and stable operation; multiple source/measure ranges with an 18-bit DAC/ADC to provide the best resolution and accuracy available with a sampling rate up to 100K s/S; programmable internal series resistance for battery simulation; ±force, ±sense and ±guards lines to avoid leakage current and reduce settling time -- especially useful for low current test applications.
The 52400 series has a patented hardware sequence engine that uses deterministic timing to control each SMU. The sequencer's on-board memory can store up to 65535 sequencer commands and 32k measurement samples per channel, allowing cross module/card synchronizat ion and latency free output control and measurement. No PC communication is required during execution of the hardware sequencer test process.
C, C#, LabView, LabWindows APIs and versatile soft front panels come standard with each SMU. The back connectors are compatible with both PXIe and hybrid chassis. All of these features enable easy integration to PXI or PXI-hybrid systems designed for a wide range of applications.
Four Quadrant Operation
All Chroma 52400 SMU series are designed for four quadrant operation for use by applications that required voltage/ current source or load simulation. During a load operation, the module is limeted by the PXI chassis’ standard of 20W heat dissipation per slot. This limit is noted as the imbalance in the quadrant diagrams for higher power models.
Below shows the quadrant diagrams of all Chroma 52400 SMU series.
Control Bandwidth Selection
To reduce test times, Chroma's SMUs are designed for fast response providing a high speed output voltage and current. The impedance of the DUT, the fixture or cabling may potentially cause the entire control loop unstable under voltage or current output mode. An unstable loop may cause saturation, oscillation or even damage the DUT. As a result, user may be asked by SMU manufacturer to add capacitor or inductor in test fixture to regain stability of the system.
Unique Hardware Sequencer
The Chroma Hardware Sequencer is a powerful tool that can predefine commands as instrument executable steps. This allows latency free control and measurement since no PC interaction required during execution. The sequence optimizes the module’s performance for application like semiconductor test where speed and timing control are critical.In this mode, once the instrument receives the start trigger, it will start to execute the commands in the sequencer table line by line or as defined upon trigger.
Guarding for Low Current Application
Guarding is an important technique for very-low current measurement. Guarding reduces Leakage Current error and decreases Settling Time. It keeps the potential of the guard connector at the same potential as the force conductor, so current does not flow between the force and guard conductors. It also eliminates the cable capacitance between source measure unit (SMU) and DUT for faster and accurate measurements.
To maximum degree of flexibility, Chroma 52400 series SMU Allows Master/Slave operation when higher current under FVMI mode is required! To ensure perfect current sharing between modules for most reliable performance, Chroma 52400 series allows only same model of channels being paralleled as higher current/ power module.
The ideal current sharing is achieved by one channel as Master and operated under FVMI mode while all the others will be set as FIMV mode. The Master channel will be programmed as application voltage desired and the analog signal of measured current will be used as the program current for rest of the FIMV channels. Figure on the right shows the configurations and connections for paralleled channels operated under Master/Slave mode.
Versatile Soft Front Panel
Before integrate the 52400 series SMU to integrated system, a versatile Soft Front Panel is provided as standard accessory which allows user to conduct verification test or debugging. This Soft Front Panel provides GUI to set the SMU output mode, range and level. The measured voltage or current reading will be shown after output is on. For modules have duel output channels, both channels can be controlled by same soft panel.
This Soft Front Panel also include control panel for hardware sequence setting described above. User can save unlimited predefined profiles to PC and recall later for different applications.
DPS & Battery Simulation for Semiconductor Test
Device Power Supply (DPS) is a voltage source used to drive semiconductor ICs. With popularity of mobile applications, the DPS can be a voltage source from DC/DC converter or sometimes battery. The long operation time requirement makes energy saving mode a common design for modern semiconductor devices. As a result, wide dynamic range of input current needs to be measured at high speed as well as high precision.
To meet this requirement, Chroma 52400 series SMU provides up to 10 current measurement ranges and 100k s/S sampling rate to ensure high speed and precision measurement for both burst or quasi-state current measurement.
In the case when battery will be used as DPS of the DUT, unique programmable resistance feature of Chroma 52400 series SMU is capable to produce voltage dip that observed in real battery setup. The voltage dip is caused by internal series resistance of battery when burst of current drain by DUT.
The Current-Voltage (I-V) Characterization is crucial to ensure FET meet specifications and work properly. These I-V tests may include gate leakage, breakdown voltage, drain current, etc. Programming and synchronizing multiple instruments is crucial to ensure correct test result. By using Chroma 52400 series SMU, user can quickly and accurately source and measure both current and voltage.
As indicated, The Force Hi (+Force) terminal of 52400 SMU CH1 is connected to the gate of the MOSFET and the Force Hi terminal of 52400 SMU CH2 is connected to the drain. The source terminal of the MOSFET is connected to the Force Lo (-Force) terminals of both SMU channels. By appropriately sweep and voltage or current on different channels, user may get various MOSFET I-V characteristics.
LED/Laser Diode Test
Light emitting devices such as LEDs or Laser Diodes requires sourcing, loading and optical power measurement when conducting parametric test for LIV as well as reverse characteristics. SMU is capable to be set as current source mode to drive the DUT to test the forward characteristics and being set as voltage sourcing mode for reverse performance.
Optical power measurement requires another measurement input. Photo diode is normally used to be an optical power sensor. The optical power is proportional to the short circuit of the photo diode, fail to bias the photo diode to zero volt may have less accurate measurement result because the forward voltage of photo diode has higher temperature coefficient impact than the short circuit current. Another important feature for SMU is, it is capable to compensate the voltage drop over the cable to ensure the photo diode to true short circuit condition while typical current shunt type of current measurement setup may cause voltage burden issue.
The duel input channels design of Chroma 52400 series SMU together with synchronous measurement is capable to cover all the test needs in one module to achieve smallest footprint and highest channel density when multiple DUTs need to be test.
Solar Cell Test
Solar Cell has diode structure which can be characterized by I-V sweep. The nature of energy generating requires the unique load sweep for light forward I-V curve that used to derive most of the important parameters of a solar cell. Voltage source will then be required for reverse performance testing. Unlike conventional diode test, both shunt and series resistors are important performance index of solar cells.
SMU can be operated as load for light forward test and also voltage source for reverse bias characterization. This unique four-quadrant operation makes SMU an ideal test instrument for solar cell.
Chroma 52400 series SMU provides synchronous measurements for voltage and current also between channels. This is important because the irradiance from solar simulator may have temporal instability which requires irradiance monitor used to correct the photon current of solar cell to 1 sun (100mW/ m2) standard irradiance condition defined by IEC-60904-1.