Coilcraft has introduced the CSX7045 series of surface-mount current sense transformers for isolated measurement of high-frequency current in power-electronics circuits.
The series combines a 5.3 mm maximum profile, 1.8 kVrms one-minute hipot isolation, current sensing above 20 A and a specified operating bandwidth extending to 800 kHz.
Key features and benefits
- Surface-mount current sense transformer family in a compact chip-style package
- 1:50 to 1:250 primary-to-secondary turns-ratio options
- Primary-current capability above 20 A
- Frequency range extending to 800 kHz
- 1800 Vrms, one-minute isolation test between primary and secondary
- Extremely low DC resistance is the manufacturer’s qualitative positioning; the current datasheet should be used for the applicable part-number value.
- Qualified based on AEC-Q200 Rev E
- 5.3 mm maximum package profile
The CSX7045 series expands Coilcraft’s current-transformer portfolio with a higher isolation rating than many compact SMT current-sensing alternatives. A current sense transformer transfers an AC or pulsed-current signal to a secondary winding while keeping the measurement circuitry galvanically isolated from the primary current path.
Technical highlights
| Parameter | CSX7045 series |
|---|---|
| Component type | SMT current sense transformer |
| Primary current | Above 20 A |
| Frequency range | To 800 kHz |
| Turns-ratio range | 1:50 to 1:250 |
| Isolation test | 1800 Vrms, 1 minute |
| Package profile | 5.3 mm |
| Qualification | AEC-Q200 Rev E |
The disclosed family name is CSX7045. The public release identifies the CSX7045-050 variant, while Coilcraft’s product documentation also identifies CSX7045-200. The announced turns-ratio range indicates that selection is intended to be made around the required output signal level, terminating resistance and volt-second margin rather than current alone.
The 1800 Vrms isolation figure is a one-minute hipot test value. It should not be treated as a complete system insulation classification without checking the final equipment’s working voltage, transient environment, creepage and clearance requirements, insulation coordination, PCB construction and applicable end-product safety standard.
AEC-Q200 is a stress-test qualification for passive components. It is not vehicle-level approval and does not by itself validate an inverter, charger, ECU or other complete automotive assembly.
Typical applications
Current sense transformers operate with changing current, so the CSX7045 series is applicable to high-frequency AC or pulsed-current measurement rather than direct DC-current measurement. The published frequency range to 800 kHz, isolation test voltage and current capability support use in switching power stages where the sensed waveform contains a suitable alternating component.
- Switch-mode DC-DC converters: Current-mode control, cycle-by-cycle current limiting and primary-side overcurrent detection can use the transformer’s isolated secondary signal when the converter waveform and switching-frequency content fall within the specified operating range.
- Motor drives and inverters: The 1800 Vrms isolation test and AEC-Q200 Rev E qualification support evaluation for isolated current feedback and protection paths in high-voltage power stages. Final suitability depends on the required functional, basic or reinforced-insulation system design.
- Power-management circuits: Turns-ratio options from 1:50 to 1:250 allow the secondary current and burden-resistor voltage to be tailored to the comparator, controller or ADC input range.
- Automotive power electronics: The qualification basis, 5.3 mm profile and current capability above 20 A make the series relevant to compact automotive converter and control assemblies, subject to full system-level qualification.
Application fit
| Circuit position | Published rating supporting evaluation | Key verification |
|---|---|---|
| Current-mode control | To 800 kHz bandwidth | Frequency and volt-second margin |
| Overcurrent protection | Above 20 A sensing | Peak fault-current waveform |
| Isolated feedback | 1800 Vrms, 1 minute | System insulation coordination |
| Compact automotive PCB | AEC-Q200 Rev E, 5.3 mm profile | End-product qualification |
For a current-mode converter, the turns ratio and burden resistor set the output voltage available to the sensing circuit. Increasing the burden resistance raises the secondary voltage for a given current, but it also changes the transformer’s flux excursion. The burden network, reset path, duty cycle and worst-case current waveform should therefore be checked together.
The 1:50 to 1:250 ratio range provides a useful selection trade-off. A lower ratio produces more secondary current for a given primary current, while a higher ratio reduces the secondary current and may help match a different sensing threshold or input range. Neither choice can be finalized without the relevant part-specific inductance, volt-time and recommended terminating-resistance data from the current datasheet.
Design-in notes for engineers
- Confirm that the measured waveform has adequate AC or switching content. A current transformer cannot provide a steady-state DC-current measurement.
- Select the turns ratio from the required primary-current range, desired signal level and the burden resistance permitted by the current part-specific datasheet.
- Check the complete current waveform, including startup, overload, short-circuit, discontinuous-conduction and abnormal operating states. Peak current and volt-second stress may be more restrictive than nominal RMS current.
- Validate the transformer’s lower usable frequency against switching frequency, duty cycle, burden resistance and reset conditions. Core saturation can distort the sensed waveform or delay a protection response.
- Treat the 1800 Vrms rating as a component isolation-test value, not as a substitute for PCB creepage, clearance, surge, pollution-degree or system-safety analysis.
- Assess primary-path copper losses, device self-heating and ambient temperature together. The manufacturer characterises the series as low loss, but a measured thermal result in the final PCB assembly is still required.
- Review the current datasheet for exact part-number electrical data, dimensions, land pattern, soldering requirements, tolerance, termination and packaging details before schematic, layout or production release.
- No public CSX7045 application note, SPICE model, S-parameter set, qualification report, product-change notice or lifecycle statement was located in the documents reviewed. Those items should be requested from Coilcraft if required for the project’s validation process.
Further reading
- Current Sense Transformer Design and Application
- Current Sense Transformers for Switched-mode Power Supplies
- Current Sense Transformer Datasheet and Design‑in Guide
Source
This article is based on the Coilcraft product announcement and official product documentation. Engineers should consult the current manufacturer datasheet and supporting documentation for final part selection, qualification and design release.
