Bourns has introduced the HCTSM100308BAL, a high clearance and creepage distance transformer optimized for compact, isolated push‑pull and similar DC/DC converter topologies.
Positioned within the HCTSM8 family, the device targets designs that must meet reinforced insulation requirements and maintain isolation in small SMD footprints under demanding thermal and electrical conditions.
Key features and benefits
The HCTSM100308BAL transformer is part of the Bourns HCTSM8 high clearance and creepage distance transformer series designed for isolated low‑power supplies in industrial, communication and related systems. It is intended to work with popular isolated driver ICs and controller devices in applications where reinforced insulation and reliable separation between primary and secondary circuits are mandatory.
Key characteristics include:
- High clearance and creepage distance between primary and secondary to support reinforced insulation.
- Working voltage capability defined in the manufacturer datasheet for the HCTSM8 series, enabling use in systems requiring robust isolation.
- Hi‑pot isolation specified in the kilovolt range (primary to secondary) according to the family datasheet, suitable for safety‑critical isolation barriers.
- Surface‑mount package optimized for automated assembly, with low profile and compact footprint.
- Ferrite core construction with insulated copper windings to support insulation requirements and minimize leakage.
- Suitability for push‑pull type isolated converters using appropriate driver ICs from major semiconductor vendors, enabling efficient energy transfer for compact gate‑drive or bias supplies.
In practice, the increased clearance and creepage distance help designers address insulation coordination aspects of IEC 62368‑1 and similar safety standards without resorting to bulky through‑hole magnetics. Using a surface‑mount transformer with reinforced insulation can simplify PCB layout, reduce board space, and support higher system reliability under long‑term thermal and electrical stress.
Typical applications
The HCTSM8 series is commonly used in small isolated power stages that provide a few watts to drive control electronics or interfaces rather than bulk power conversion. The HCTSM100308BAL variant targets similar use cases where small size and high isolation are required at the same time.
Typical applications include:
- Isolated bias supplies for gate drivers, for example IGBT or MOSFET drivers in industrial inverters and motor drives.
- Isolated auxiliary DC/DC converters from low‑voltage rails to support measurement, communication or control circuitry.
- Isolated power for communication interfaces or sensors in industrial control and automation.
- Circuits requiring reinforced isolation and compliance with insulation coordination rules, such as parts of medical, industrial or instrumentation systems, within the ratings specified in the datasheet.
In these use cases, the transformer helps break ground loops, improves EMC behavior for sensitive electronics, and offers a compact way to implement safety‑compliant isolation between primary and secondary circuits.
Technical highlights
The HCTSM100308BAL follows the general electrical and mechanical framework of the HCTSM8 series while using a compact SMD footprint. Exact primary inductance, turns ratio, current ratings and detailed safety classifications should always be taken directly from the manufacturer datasheet for the HCTSM100308BAL ordering code.
Key technical characteristics at HCTSM8 family level, indicative for this model, include:
- Input voltage range for typical designs around low‑voltage rails such as 3.3 V to 5 V DC.
- Output voltage range on the order of a few volts up to about 15 V DC, depending on turns ratio and converter design.
- Peak output current capability in the few hundred milliampere range, suitable for bias and auxiliary rails rather than high‑power conversion.
- Operating frequency range in the typical few‑hundred‑kilohertz band, matching common push‑pull driver ICs.
- Operating temperature rating up to 125 °C including temperature rise, supporting use in thermally demanding environments.
- Clearance and creepage distance between primary and secondary on the order of several millimeters, sufficient for reinforced insulation when applied according to the datasheet.
Mechanically, HCTSM8 devices are specified around a compact rectangular SMD package; the series includes a reduced‑length variant such as HCTSM80308BAL, and the exact mechanical outline of HCTSM100308BAL should be confirmed in the official drawing. The SMD package is supplied on tape‑and‑reel to support high‑volume automated pick‑and‑place assembly, and the recommended reflow profile is aligned with standard lead‑free soldering processes.
For practical design work, parameters such as primary inductance, leakage inductance, ET constant and DC resistance allow engineers to model core and copper losses and to estimate efficiency over the intended load current and operating frequency. Efficiency and thermal behavior should be validated at system level, but the family’s datasheet curves provide a useful starting point when sizing the transformer and checking margin.
Design‑in notes for engineers
When designing in the HCTSM100308BAL, a good starting point is the reference push‑pull or similar isolated converter topology recommended by Bourns and by the chosen driver IC manufacturer. The transformer’s turns ratio, inductance and current rating must be matched to the input voltage, target output voltage, switching frequency and expected load profile.
Key design‑in considerations include:
- Use the HCTSM100308BAL‑specific inductance, leakage inductance and DC resistance values from the datasheet as the basis for SPICE models and loss calculations.
- Check the rated ET constant and ensure that the applied volt‑microsecond product of the waveform remains within limit at the chosen switching frequency and duty cycle.
- Respect the specified Hi‑pot and reinforced insulation ratings by following the recommended land pattern so that creepage and clearance distances on the PCB are not reduced.
- Pay attention to any suggested slots, keep‑out areas or solder mask openings that help maintain isolation distance and reduce surface contamination effects.
- Follow the recommended soldering profile and avoid exceeding maximum temperature limits during reflow, to protect the magnetic core and insulation system.
From an EMC and signal integrity perspective, the HCTSM8 construction is intended to support low leakage and good coupling, which helps reduce stray fields and supports compliance with conducted and radiated emission limits. Even so, designers should validate emissions, conducted noise and transient behavior in the final assembly, because board layout, grounding strategy and neighboring circuits strongly influence overall EMC performance.
For long‑term reliability, pay close attention to ambient temperature, self‑heating due to copper and core losses, and the maximum operating temperature rating up to 125 °C stated for the series. In higher ambient conditions it can be beneficial to derate output power or adjust frequency and duty cycle so that the transformer operates with sufficient thermal margin and insulation life over the required service period.
Source
The information in this article is based on the Bourns featured product bulletin for the HCTSM100308BAL and on the HCTSM8 series datasheet and related magnetics application material provided by the manufacturer.