Compact automotive photorelay with high breakdown voltage support for EV battery systems

Toshiba Electronics Europe GmbH has introduced a new automotive photorelay, the TLX9161T. Housed in a small SO12L-T package, the device attains an output withstand voltage (VOFF) of 1500V (min.) with a reaction time (TON/TOFF) of 1ms (max.). This capability is vital for supporting the demanding high-voltage requirements of modern automotive battery and fuel-cell control and BMS, which monitor voltage and detect mechanical relay sticking and ground faults. These photorelays are also excellent for replacing conventional mechanical relays.

The device consists of an IR LED optically coupled to a photo-MOSFET, ensuring that the primary (control) side and the secondary (switch) side are electrically isolated. The high isolation voltage of 5000Vrms facilitates safe switch control across varying potentials. The trigger current (IFT) is 3mA (max.), which minimises system energy consumption. Also, this device’s off-state current (IOFF) is just 100nA (max.) at ambient temperature, drawing minimal power while inactive. The IR LED forward current (IF) and the detector element’s on-state current (ION) are rated at 30mA ambient.

By decreasing the size of the built-in MOSFET chip, the company has enabled the new photorelay to be housed in a SO12L-T package, which is approximately 25% smaller than the SO16L-T package used for its predecessor, the TLX9160T. This reduction helps minimise the overall size of the battery unit and allows for cost savings. Despite the smaller package, the device maintains the same pin pitch and pin layout as the SO16L-T, allowing for common use of circuit board pattern designs. The typical dimensions of the SO12L-T package are 7.76mm × 10mm × 2.45mm.

Safety and compliance are paramount in automotive applications. The TLX9161T utilises a resin with a CTI exceeding 600, classifying it under Material Group I according to the international standard IEC60664-1. This standard specifies principles, requirements, and test methods for insulation coordination for systems up to 1000VAC or 1500VDC. The normally-open (1-Form-A) device displays creepage and clearance distances of 8mm (min.), confirming effective isolation even in operating temperatures ranging from -40C to +125C, making it fully compliant with AEC-Q101 Grade 1.