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- CT04 Series
Key Features
- Low-profile SMT current-sense transformer (4.10 mm height)
- Compact 6.9 mm × 8.13 mm PCB footprint
- Supports primary currents up to 20 A
- Supports SMPS switching frequencies up to ~1.5 MHz
- Turns ratios from 1:50 to 1:125
- 500 VAC primary-to-secondary isolation (Hi-Pot tested)
- Reflow-ready SMT design with tape-and-reel packaging
- Suitable for pick-and-place assembly
APPLICATIONS
- DC/DC converters for industrial, telecom, and embedded systems
- AC/DC power supplies and front-end conversion stages
- POL (Point-of-Load) regulators requiring precise inductor current sensing
- Feedback and current-mode control loops in switching power supplies
- Overload, short-circuit, and protection monitoring circuits
- Distributed power systems and board-level current measurement
- DC/DC converters for industrial, telecom, and embedded systems
- AC/DC power supplies and front-end conversion stages
- POL (Point-of-Load) regulators requiring precise inductor current sensing
- Feedback and current-mode control loops in switching power supplies
- Overload, short-circuit, and protection monitoring circuits
- Distributed power systems and board-level current measurement
Electrical Specifications @ 25°C - Operating Temperature Range1: -40°C to +130°C
Part Number
Turns Ratio
(TR)
Secondary Inductance2
(μH, Min)
Secondary DCR
(Ω, Max)
Current Rating4
(A, Max)
SRF5 (6-4)
(MHz, Typ)
ET Product8
(V-μs, Max)
Hi Pot
(VAC)
Mechanical Drawing
Recommended PCB Layout
Schematic
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Operating Temp. Range: The combination of ambient temperature and temperature rise.
-
Secondary Inductance: Tested at 10kHz, 1VRMS.
-
Primary DCR (8-7): 0.4 mΩ (Ref)
-
Current Rating: Peak current (50% duty cycle) through primary (8-7) to cause 40°C temperature rise at 25°C ambient.
-
SRF: Values are for reference only.
-
Flammability Standard: Meets UL 94V-0.
-
Terminating Resistor (RB): To calculate the value use the formula,
RB = EOTR/IP -
ET Product: The maximum ET is based upon a flux density of 3700 Gauss at 25°C. Suitable for bipolar applications only.
ET = EO/2f
EO = IPRB/TRWhereas,
EO = Output voltage (V) TR = Turns Ratio
RB = Term. Resistor (Ω) f = Frequency (Hz)
IP = Primary Current (A) -
PACKAGING
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Reel Diameter: 13”
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Reel Width: 16mm
-
Pieces/Reel: 1200
-
-
Compliance & Solutions:
-
Specifications subject to change without prior notice.
Frequently Asked Questions (FAQs)
How do I choose the correct turns ratio for CT04?
Choose the turns ratio based on the sense-voltage requirements of your controller and the expected primary current range. Lower ratios (1:50) are suited for higher-current rails, while higher ratios (1:125) generate more output voltage for lower-current sensing. Ensure the chosen combination complies with the ET-product and burden resistor recommendations from the datasheet.
What burden resistor should I use with CT04?
Select a burden resistor that provides adequate sense voltage while keeping the transformer within its ET and thermal limits. The datasheet’s calculation guidance helps ensure the resistor value supports accurate waveform reproduction without overloading the transformer or controller input.
Can CT04 be used with current-mode SMPS controllers or protection circuits?
Yes. CT04 works effectively in current-mode control loops, average-current regulation, and over-current detection. When optimally paired with appropriate burden and filtering, it generates a clean, isolated sense signal compatible with standard SMPS controllers.
Does CT04 require specific PCB design practices for best accuracy?
For best performance, route the primary current path with minimal loop area, keep the burden resistor close to the transformer’s secondary pins, and avoid placing high dV/dt switching nodes near the sense lines. These practices help ensure signal clarity and reduce coupling noise.
Can CT04 measure pulsed or non-sinusoidal currents typical of switch-mode converters?
Yes. CT04 is designed for switch-mode current sensing and can accurately measure pulsed or triangular inductor currents as long as operating conditions remain within ET-product and burden resistor limits.
Is CT04 suitable for higher-frequency SMPS designs?
Yes. With typical self-resonant frequencies around 1 MHz (varying by part number), CT04 supports many high-frequency SMPS applications. Proper burden value, filtering, and PCB layout help maintain waveform accuracy approaching the upper frequency range.
What isolation rating does CT04 provide?
CT04 provides 500 VAC primary-to-secondary isolation, offering safe electrical separation between the sensed current path and low-voltage monitoring circuitry.
What environmental conditions can CT04 withstand?
The CT04 Series is rated for –40 °C to +130 °C, enabling stable operation in demanding industrial, telecom, and high-density power environments.
How is CT04 typically connected into the current path?
The sensed current is routed through the primary pins of the transformer. The secondary winding, combined with the burden resistor, generates a scaled and isolated voltage proportional to the measured current for use by the controller or monitoring circuit.
Where can I download datasheets, models, and technical resources?
The CT04 product page provides downloadable datasheets, mechanical drawings, layout guidance, and options to request SPICE or 3D CAD models for integration into design workflows.