YAGEO Group has introduced the PMT6397 series of surface-mount push-pull transformers for isolated power supplies delivering up to 3 W.
Part of the YAGEO PTPA extended-creepage toroidal platform, the series combines segmented windings, 17.6 mm creepage and 13 mm clearance with three centre-tapped turns ratios. Selection depends on the required insulation class, winding volt-seconds and thermal operating conditions.
Key features and benefits
- Three winding configurations: 1CT:1CT, 1CT:3CT and 3CT:4CT.
- Segmented toroidal windings with triple-insulated wire.
- Maximum interwinding capacitance of 7.0–8.0 pF, depending on the model.
- Isolation voltage of 5,000 V RMS.
- Partial-discharge-based repetitive peak voltage ratings of 1,500 V peak for basic insulation and 1,200 V peak for reinforced insulation.
- Maximum package dimensions of 18 × 14 × 12.3 mm.
- Operating temperature range of −40 °C to +125 °C.
- Tape-and-reel packaging with 150 components per reel.
Technical highlights
Three turns ratios and different magnetic limits
The PMT6397 series operates in a fixed-duty-cycle push-pull converter topology. Each model has centre-tapped primary and secondary windings, but its inductance, winding resistance and maximum volt-second product differ.
Electrical characteristics below apply at 25 °C. Primary inductance and maximum volt-seconds refer to winding terminals 1–2.
| Part number | Turns ratio | Primary inductance, min. | Volt-seconds, max. |
|---|---|---|---|
| PMT6397.011NLT | 1CT:1CT | 140 µH | 54 V·µs |
| PMT6397.013NLT | 1CT:3CT | 70 µH | 38 V·µs |
| PMT6397.034NLT | 3CT:4CT | 115 µH | 48 V·µs |
The volt-second limits are based on operation at 300 kHz with a bipolar peak flux swing of 180 mT. They constrain the combination of winding voltage and excitation time; turns ratio alone is not sufficient to select a transformer.
| Part number | Primary DCR, max. | Secondary DCR, max. | Interwinding capacitance, max. |
|---|---|---|---|
| PMT6397.011NLT | 0.70 Ω | 0.70 Ω | 8.0 pF |
| PMT6397.013NLT | 0.50 Ω | 1.20 Ω | 7.5 pF |
| PMT6397.034NLT | 0.65 Ω | 0.75 Ω | 7.0 pF |
Primary DCR applies to each half-winding, terminals 1–2 and 3–4. Secondary DCR applies to terminals 5–6 and 7–8. Interwinding capacitance is measured between terminals 1,3 and 6,8.
Maximum leakage inductance is 12 µH for PMT6397.011NLT, 7 µH for PMT6397.013NLT and 11 µH for PMT6397.034NLT. These values apply to terminals 1–4 with terminals 5–8 shorted and the centre-tap connections tied.
Insulation ratings: distinguish working voltage from test voltage
The insulation requirement determines which voltage rating governs selection. The 5,000 V RMS isolation rating is distinct from both the continuous working-voltage limits and the repetitive peak voltage ratings established through partial-discharge testing.
| Parameter | Basic insulation | Reinforced insulation |
|---|---|---|
| Working voltage | 1,760 V RMS | 880 V RMS |
| Repetitive peak voltage | 1,500 V peak | 1,200 V peak |
| Creepage distance | 17.6 mm | 17.6 mm |
| Clearance distance | 13 mm | 13 mm |
The working-voltage values follow IEC 61558-1 and IEC 61558-2-16 under material group III, pollution degree 2, overvoltage category II and an altitude of 5,000 m.
The repetitive peak voltage ratings use partial-discharge testing under IEC 60664, with discharge below 10 pC. This assessment addresses insulation behaviour under repetitive voltage stress rather than treating the isolation-test voltage as a continuous operating limit.
Segmented winding construction
The toroidal winding arrangement separates the primary and secondary winding sections. Triple-insulated wire forms part of the insulation system, while the package positions the coil above the terminals to establish the extended creepage path.
Interwinding capacitance is a relevant selection parameter for wide-bandgap switching applications. The model-specific maximum matters alongside the insulation rating: the three turns-ratio options do not share an identical capacitance limit.
Typical applications
Target applications include:
- EV charging equipment.
- Motor drives.
- Inverters.
- Power supplies.
- High-frequency switching systems.
Within these systems, the PMT6397 serves as a transformer for an isolated auxiliary supply delivering up to 3 W, rather than as the main power-conversion transformer.
A typical implementation is an isolated automotive power-supply driver circuit. The series is compatible with the TI SN6501-Q1 and other automotive-grade push-pull drivers.
The PMT6397.013NLT has a 1CT:3CT ratio intended to support an output of up to 15 V from a 5 V source. The other variants provide 1CT:1CT and 3CT:4CT winding-voltage relationships for different supply requirements.
Design-in notes for engineers
- Match the insulation class to the barrier requirement. Use the applicable working-voltage and repetitive peak voltage limits separately from the 5,000 V RMS isolation rating.
- Check the applied winding volt-seconds against the selected model’s limit. Operation above 300 kHz may require further volt-second derating because of core and copper losses.
- Assess winding RMS currents and resistance together. Copper loss and core loss both contribute to temperature rise, so the up-to-3 W power capability should not be treated independently of thermal conditions.
- Preserve the insulation spacing in the PCB layout. Component creepage and clearance are part of the complete isolation-barrier design.
- Use the mechanical drawing and terminal arrangement when establishing the footprint and centre-tap connections.
- Validate the selected transformer under the actual electrical, thermal and insulation conditions before production release.
Further reading
- Transformer Topologies in Power Converters
- Transformer Types and Applications
- How to Select the Right Transformer for High Voltage Energy Storage Applications
Source
This article is based on the YAGEO Group product announcement and official product documentation. Engineers should refer to the current manufacturer datasheet for final design and qualification.
References
- PMT6397 Series PTPA Push-Pull Transformers, YAGEO Group.
- Push Pull Transformer — Extended Creepage Toroidal Platform SMD, PTPA Series, P952.A, YAGEO Group, June 25, 2026.
- PMT6397 Series Product Brief, YAGEO Group, October 2025.
- How Does It Work? Partial Discharge Testing Explained, YAGEO Group.
