50 mA Source Measure Unit

The 50 mA Source Measure Unit is a highly specialized and precise instrument tailored for testing and characterizing low current semiconductor devices including light emitting devices, such as VCSEL singlets, single emitters, microLED. The ability to provide both DC current and precision pulsed current with excellent pulse fidelity at low currents is crucial for accurately assessing the performance and characteristics of these devices.

---

---

Applications

---

50 mA Source Measure Unit Specifications

50 mA Source Measure Unit Specifications	50 mA (Max Current)
Overall
Min Output Voltage	0 V
Max Compliance Voltage	50 V, 100 V, 200 V, 400 V
Source Channels	1
Max DC Output Power	5 W
Max Pulsed Out Power	5 W

50 mA Source Measure Unit Specifications	50 mA (Max Current)
Pulsing
Pulse Width Range	10 μs minimum to 15000 s
Pulse Width Resolution	0.1μs (11 ns w/ Pulse Width Offset)
Pulse Width Accuracy	1μs (50 ns w/ Pulse Width Offset)
Pulse Rise/Fall Time	200 ns – 3 μs
Typical Pulse Width Jitter	30 ns
Timebase Accuracy	50 ppm
Pulse Period Range	11μs – 30000 s, depending on model
Duty Cycle Range	Programmable 0-100%, no current limits, limited by Toffmin of 20 μs or 9 μs (1μs model)
Pulse Count	0 – 12000000 (Multiple Pulse and Pulsed Sweep modes)
Sweep Steps	3 – 10000 (Pulsed Sweep mode)
Low Range Current
Max Current	4 mA
Setpoint Resolution	100 nA
Output Current Accuracy	0.05% + 6 μA
Min Recommended Current	6 μA
High Range Current
Max Current	50 mA
Setpoint Resolution	1 μA
Output Current Accuracy	0.05% + 10 μA

---

Digitizer Specifications

Digitizer Channels	1,2
Measure Method	4 wire
Ranges	3 Ranges, 10 V, 100 V and 400 V
Input Impedance	1 MΩ -1.4 MΩ
Disconnect Relay	Disconnect Sense +/- terminals when Digitizer is placed in 0 V range
Coupling	DC Coupled, All Ranges
Maximum Common Mode	Sense+ or Sense- must be <420 VDC from Chassis Ground or Force+ or Force-
ADC Sample Rate	500,000 samples/second, continuous sampling
Digitizer Type	True differential
Resolution	18 Bits
Programmable Measurement Aperture	2 μs to 400 ms, 500 kHz samples boxcar averaged to form measurement points
Measurement Trigger	Software or hardware
Hardware Trigger Edge Polarity	Programmable
Trigger Delay	Programmable 0 to 400 ms, 2 μs resolution
Measurement Points Per Acquisition	1 to 525
Autozero Function	Reduces measurement offset
Sampling Method	Logarithmic sampling to 1000 s, and custom programmable sampling available with +BIAS option

Digitizer Range Specifications

Ranges	10 V	100 V	400 V
Maximum Voltage	10.4 V	112.2 V	420.6 V
Typical Noise, RMS	100 μV	200 μV	500 μV
Bandwidth (-3dB)	570 kHz	290 kHz	570 kHz
Accuracy	0.03% + 300 μV	0.09% + 3 mV	0.06% + 30 mV

---

General SpikeSafe SMU Specifications

Current Out
Digitizer Channels	1,2
Output Current Drive Type	Floating, both + and – terminal driven, max 100 V common mode to chassis ground
Output Cabling	Single or multi-conductor twisted pair
Recommended Max Output Cable Length	6 m
Trigger In
Signal Type	5 V logic, VIH > 3.5 V, VIL < 1.5 V
Polarity	Programmable
Modes Supported	Multiple Pulse, Pulsed Sweep, Modulated Current
Programmable Delay	Programmable delay, 10 μs to 30 s
Delay Programming Resolution	1 μs
Delay Jitter	Multiple Pulse Mode: 3.4 μs, Pulsed Sweep Mode: 107 μs
Trigger Out
Signal Type	5 V logic, 50 Ω pull-up and open drain outputs
Polarity	Programmable
Modes Supported	All pulsed modes, Software trigger in DC mode
Trigger Jitter	<10 ns typical
Programmable Delay	Programmable delay, 10 μs to 30 s
Miscellaneous
Nominal Current Ripple	<1mA: 4 μA 1 mA to 10 mA: 40 μA 10 mA to 50 mA: 17 0μA
DC Ramp Rate: Low Speed Setting	10 V/s, 50 mA/s
DC Ramp Rate: Default Setting	10 V/s, 500 mA/s
DC Ramp Rate: High Speed Setting	1000 V/s, 50 A/s
Current Stability	70 ppm
SpikeSafe Transient Protection	Power shutdown timing ns. (voltage monitor accuracy: 3% +1 V | current monitor accuracy: model dependent)
Other External Factors
General Purpose Input (EXT_GPI)	Optoisolated input, generates External Pause SYST:ERR? Event, VLow Max: 0.75 V, VHigh Min: 2.72 V, VHigh Max: 27.2 V
Remote Disable (Interlock)	Optoisolated input, halts output, selectable polarity, VLow Max: 0.75 V, VHigh Min: 2.72 V, VHigh Max: 27.2 V
General
Physical	Rack mount/bench top chassis 1/2 Rack 89 mmH x 213 mmW x 452 mmD Weight: 8 lbs, 3.6 kg
Input Power	AC 100-240 VAC, 700 W, Single Phase
Remote Control	100-base T Ethernet, TCP/IP with SCPI syntax
Monitoring System	Built-in acquisition system monitors & reports voltage, current, and fault conditions
Device Protection	3rd generation SpikeSafe protection including high-speed over current shutdown, slow start up, leakage detection and other protection algorithms
Calibration Interval	1 year calibration interval recommended
Operating Conditions	For indoor use only, 10 C to 35 C, <2000 m altitude
Cooling	Air cooled
Particulate Level	Clean lab conditions
Other	CE, ROHS, ISO17025 certification

---

Configuration Options

---

---

---

Operating Modes

Operating Mode	Description	Typical Application
Bias	Constant DC bias current – generally used for SVF (voltage sensitivity factor) determination.	Thermal Resistance and Tj measurements. Bias may be added to many operating modes. Requires purchase of optional BIAS.
Continuous Dynamic	Continuous pulse train – current changes may occur while the source channel is enabled.	PWM, production binning, closed-loop power control.
Continuous Pulse	Continuous current pulse train that transitions on and off according to configured pulse parameters.	Continuous pulse light measurements to reduce junction heating. Any other continuous pulse application.
CW Sweep	Constant wave current sweep.	Typical characterization test where output parameters like power are monitored over a range of input power levels.
DC	Direct current. Also known as constant current or constant wave. DC dynamic mode allows current to be changed +/- during DC operation.	Any constant current application. LM-85, light measurement, characterization, R&D, production.
DC Dynamic	Constant current – current changes may occur while the source channel is enabled.	Low speed > 10s pulsing. Software controlled pulsing. Useful for TEC control.
Modulated Current	A programmable sequence of DC current steps that define a waveform. Sequences may be finite or run indefinitely.	Cell phone flash emulation, rectifier ripple emulation. Requires purchase of optional Modulated Current function.
Multiple Pulse	Similar to Single Pulse mode, but allows a programmable number of pulses to be output.	Fixed pulse count device testing. Also recommended for Single Pulse use (1 pulse).
Multiple Pulse Burst	Multiple bursts of pulses with defined pulse and burst timing, and current changes.	Burst L-I-V sweeps, high duty cycle sweeps.
Pulsed Sweep	Also known as QCW (quasi-constant wave). Primarily used to minimize self-heating such as with I-V, L-I, and LIV curves. Pulsed sweep on/off may be used to thermally stress devices or speed lifetime test. Also used for withstand or limit testing. Step number reported at error used to identify failure current.	I-V plots for LEDs, lasers, and other semiconductors. L-I plots for optoelectronics, overcurrent protection circuit tests, pulse withstand testing.
Repetitive Burst Mode	Multiple bursts of bursts.	VCSEL testing. Customer specific applications.
Single Pulse	Also known as mono pulse. One pulse output (one transition on and off) according to configured pulse parameters.	Any single pulse application. LM-85, light measurement, characterization, R&D, production.

---

Contact Us

Accurate currents combined with fast rise and fall times plus a precision hardware-controlled timing system that synchronizes source, measure and external instrumentation allow for discovery at low currents.

---

Related Software

💡 Python and API Examples
💡 Control Panel Software Application