UM8-40 Series

  • 8kV to 40kV, Fixed Negative or Positive Polarity
  • Output Power of 4, 15 and 30 Watts
  • V/I Regulation with Automatic Crossover Control
  • V/I Monitor Signals; +5V Ref Output
  • CE listed and RoHS compliant

DC-DC High Voltage Power Supplies

Form, Fit and Function Design: 

Spellman’s UM Series of printed circuit board mountable, high voltage modules offer a form, fit and function replacement for presently available commercially made units, while providing additional features and benefits at competitive pricing. Utilizing proprietary power conversion technology and Spellman's six decades of high voltage experience, these SMT based high voltage modules provide improved performance/reliability and easier system integration at a lower cost when compared to the competition.

Advanced Power Conversion Topology:

UM converters use a proprietary zero voltage switching power conversion topology providing exceptional efficiency and inherent low noise and ripple. Radiated emissions are reduced compared to conventional switching topologies, minimizing or even eliminating the need to shield the unit from adjacent circuitry. 

The high voltage output is generated using a ferrite core high voltage step up transformer which feeds a half wave Cockcroft-Walton voltage multiplier to obtain the specified high voltage output. 
Due to the fixed, high frequency conversion rate the output capacitance is small resulting in minimal stored energy. Through the use of generously rated surge limiting resistors and a fast acting current loop, all units are fully arc and short circuit protected.

Control and Regulation:

The actual output voltage generated is sampled via a high impedance divider to create a voltage feedback signal. A current feedback signal is created via a current sense resistor in the low end return of the high voltage output circuitry. These two accurate ground referenced feedback signals are used to precisely regulate and control the units in addition to external monitoring purposes. 

Due to the UM’s unique converter topology it can provide full current into low impedance loads or even a short circuit. Standard units limit at 103% of maximum rated output current.

Standard Interface:

The Spellman UM Series interface provides current programming capability and positive polarity, buffered, low output imped­ance voltage and current monitor signals (zero to +4.64Vdc equals zero to full scale rated). A voltage programming input is provided where 0 to +4.64Vdc equals 0 to 100% of rated voltage. 

Current programmability allows the user to set where the unit will current limit, anywhere from 0 to 100% of maximum rated current. This feature is beneficial where less than full output current is desired, like in the case of protecting a sensitive load. 

The buffered low impedance voltage and current monitor signals can drive external circuitry directly, while minimizing loading and pickup effects. These features save the user the expense and implementation of external interface buffering circuitry while improving overall signal integrity.  

This standard interface is made available via a row of 13 pins with 0.1. pin spacing. A legacy interface (7 pins on a 0.2. spacing) that is compatible with presently available commercially made units can be provided by ordering the “L” option.

Mechanical and Environmental Considerations:

The UM Series are solid encapsulated, printed circuit board mountable, plastic cased converters. All units are encapsulat­ed using a silicon based potting material which is consider­ably lighter in weight than epoxy. Isolated, non grounded 2-56 machine screws thread into the module to securely mount it to the printed circuit board, relieving any stress on the interface pins. Mounting plates, brackets and flanged mounting options are also available. High voltage output is provided via a 36. (914.4mm) minimum length of appropriately rated high volt­age wire. 

Regulatory Approvals: 

Compliant to 2004/108/EC, the EMC Directive and 
2006/95/EC, the Low Voltage Directive. RoHS compliant. 
UL/CUL recognized, File E227588.



(Rev. 128074-001 REV. L)

Input Voltage: 

12Vdc for 4W, 24Vdc for 15W and 30W 

Nominal Voltage Range: 

11Vdc to 30Vdc for 4W, 23Vdc to 30Vdc for 15W and 30W 4W units can operate at 24Vdc input with no deratings or damage to unit 

Input Current: (typical) 

Disabled: 10mA @ 24Vdc

Full output, no load: 160mA @ 24Vdc, 300mA @ 12Vdc

Full output, full load: 

4 watt units: 330mA @ 24Vdc, 640mA @ 12Vdc

15 watt units: 850mA @ 24Vdc

30 watt units: 1590mA @ 24Vdc 

Voltage Regulation: 

Line: <0.01% Load: <0.01% 

Current Regulation: 

Line: <0.01% Load: <0.01% 


0.01% per 8 hours, 0.02% per day after 30 min. warmup 


2% on all programming and monitoring, except I Sense 10% 

Temperature Coefficient: (typical) 

Standard: 100ppm/°C 

Optional: 25ppm/°C (T Option)


Temperature Range: 

Operating: -40°C to 65°C case temperature 
Storage: -55°C to 105°C, non operational

Humidity: 10% to 90%, non-condensing. 


Convection cooled, typical. 30 watt units operating at full power might require additional cooling to maintain case temperature below 65°C. Methods may include: forced air cooling, use of heat sink or metal case, etc. It is the user’s responsibility to maintain the case temperature below 65°C. Damage to the power supply due to inadequate cooling is considered misuse and repairs will not be covered under warranty.  


8kV-12kV: 3.700. L X 1.500. W X 0.990. H (93.98mm X 38.10mm X 25.03mm)

15kV-20kV: 4.700. L X 1.500. W X 0.990. H (119.38mm X 38.10mm X 25.03mm)

25kV-40kV: 6.960. L X 1.600. W X 1.14. H (176.78mm X 40.84mm X 28.87mm) 


8kV-12kV:  5.7 ounces (162 grams), typical  
15kV-20kV:  7.2 ounces (204 grams), typical  
25kV-40kV:  13.1 ounces (371 grams), typical

Output Cable:

UM8, UM10, UM12, UM15: TV20 (min. length, 36. (914.4mm)

UM20, UM25: TV30 (min. length, 36. (914.4mm)

UM30, UM35, UM40: TV40 (min. length, 36. (914.4mm)

See product PDF for more specification and features.


Model Number Output V Output Current Ripple(max) %Vp-p Output Capacitance Arc Limiting Resistance I Sense Scaling Full Scale Signal High Voltage Divider Resistance
UM8*4 0 to 8kV 0.5mA 0.05 6830pF 50kΩ 5V 200MΩ
UM10*4 0 to10kV 0.4mA 0.05 4380pF 50kΩ 2.4V 300MΩ
UM12*4 0 to 12kV 0.333mA 0.05 4380pF 50kΩ 3.33V 300MΩ
UM15*4 0 to 15kV 0.266mA 0.05 3220pF 100kΩ 1.69V 400MΩ
UM20*4 0 to 20kV 0.2mA 0.05 2310pF 100kΩ 1.316V 550MΩ
UM25*4 0 to 25kV 0.16mA 0.05 1540pF 100kΩ 1.1V 800MΩ
UM30*4 0 to 30kV 0.133mA 0.05 1370pF 120kΩ 0.95V 900MΩ
UM35*4 0 to 35kV 0.115mA 0.05 1370pF 140kΩ 0.72V 900MΩ
UM40*4 0 to 40kV 0.1mA 0.05 1370pF 140kΩ 1.3V 900MΩ


Model Number Output V Output Current Ripple(max) %Vp-p Output Capacitance Arc Limiting Resistance I Sense Scaling Full Scale Signal High Voltage Divider Resistance
UM8*15 0 to 8kV 1.875mA 0.05 6830pF 50kΩ 3.75V 200MΩ
UM10*15 0 to 10kV 1.5mA 0.05 4380pF 50kΩ 8.152V 300MΩ
UM12*15 0 to 12kV 1.25mA 0.05 4380pF 50kΩ 5V 300MΩ
UM15*15 0 to 15kV 1mA 0.05 3220pF 100kΩ 5.53V 400MΩ
UM20*15 0 to 20kV 0.75mA 0.05 2310pF 100kΩ 4.21V 550MΩ
UM25*15 0 to 25kV 0.6mA 0.05 1540pF 100kΩ 3.42V 800MΩ
UM30*15 0 to 30kV 0.5mA 0.05 1370pF 120kΩ 2.89V 900MΩ
UM35*15 0 to 35kV 0.429mA 0.05 1370pF 140kΩ 2.39V 900MΩ
UM40*15 0 to 40kV 0.375mA 0.05 1370pF 140kΩ 4.21V 900MΩ


Model Number Output V Output Current Ripple(max) %Vp-p Output Capacitance Arc Limiting Resistance I Sense Scaling Full Scale Signal High Voltage Divider Resistance
UM8*30 0 to 8kV 3.75mA 0.05 6830pF 50kΩ 5.36V 200MΩ
UM10*30 0 to 10kV 3mA 0.05 4380pF 50kΩ 7.87V 300MΩ
UM12*30 0 to 12kV 2.5mA 0.05 4380pF 50kΩ 5V 300MΩ
UM15*30 0 to 15kV 2mA 0.05 3220pF 100kΩ 5.29V 400MΩ
UM20*30 0 to 20kV 1.5mA 0.05 2310pF 100kΩ 8.15V 550MΩ
UM25*30 0 to 25kV 1.2mA 0.05 1540pF 100kΩ 6.56V 800MΩ
UM30*30 0 to 30kV 1mA 0.05 1370pF 120kΩ 5.52V 900MΩ
UM35*30 0 to 35kV 0.857mA 0.05 1370pF 140kΩ 4.66V 900MΩ
UM40*30 0 to 40kV 0.75mA 0.05 1370pF 140kΩ 8.15V 900MΩ


Pin Signal Parameters
1 Power Ground Return +12Vdc or +24Vdc power return/HV return
1A Signature Resistor Unique Identifying resistor connected to ground
2 + Power Input +12Vdc or +24Vdc power input
2A OT Output +5Vdc @ 1mA = Over Temp fault
3 I Sense See I Sense text and tables for details
3A I Mon 0 to 4.64Vdc = 0 to 100% rated output. Zout < 10kΩ
4 Enable Input Low (<0.7V, Isink@1mA)=HV OFF,
High (open or >2V)=HV ON
4A V Mon 0 to 4.64Vdc = 0 to 100% rated output. Zout < 10kΩ
5 Signal Ground Signal Ground
5A I Pgm 0 to 4.64Vdc = 0 to 100% rated output. Zin > 47kΩ
Leave open for preset current limit @103% of rated output current
6 Remote Adjust Positive Polarity Unit:
0 to +4.64VDC = 0 to 100% rated voltage,
Zin >1MΩ
Negative Polarity Unit:
+5VDC to 0.36V = 0 to 100% rated voltage,
Zin >100kΩ
Leave open if pin 6A (VPgm) is used for programming
6A V Pgm 0 to 4.64Vdc = 0 to 100% rated voltage. Zin > 100kΩ Leave open if pin 6 (remote adjust) is used for programming
7 +5V Reference Output +5Vdc ±1%, 25ppm/°C. Zout =475Ω
8 HV Ground Return HV Ground Return
9 E Out Monitor 1000:1 ratio. Polarity of Voltage Monitor signal equals polarity of unit. Accuracy is ±2%, 100ppm/°C. Calibrated with DVM with 10MΩ input impedance

Tables & Diagrams


15 PIN - Standard Interface

UM8-40 High Voltage Power Supply (Image 9) 

9 PIN - Legacy Interface

UM8-40 High Voltage Power Supply (Image 10)

Note: All specifications are subject to change without notice. Please consult the PDF version of this datasheet for the most up-to-date revision.