Automotive-Grade Photocouplers and Photorelays

Toshiba’s automotive-grade components are designed to maximize performance in the most rigorous of automotive applications. Due to increased market demand for electric vehicles, more devices are required to provide isolation across several voltage levels in areas such as battery management systems (BMS), inverters, and DC/DC converters. Additionally, photorelays are a great solid-state replacement for a traditional mechanical relay. One of the main benefits of using photorelays versus mechanical relays is reliability and longevity, which is especially important in vehicles that have longer lifetimes.

Photocouplers

Toshiba automotive photocouplers are available in four families: IC outputs with several configurations, transistor outputs, and photovoltaic outputs and MOSFET outputs (called photorelay). All isolation voltages are guaranteed for 3750 V_RMS.

IC Output

Ranging from 1 Mbps to 20 Mbps, these photocouplers are ideal for communicating over an isolation barrier. Output configurations are either open collector or totem-pole structured. All these IC output photocouplers come in a 5-pin 3.7 mm × 7.0 mm × 2.1 mm SO6 package.

Transistor Output

The photocoupler employs a transistor output within the internal structure; therefore, the main characteristics are like those of a transistor. The current transfer ratio (CTR) varies between 50 and 900, and V_CEO is either 40 V or 80 V, depending on preference V_CE(sat) and I_C(max) are constant at 0.4 V and 0.05 A, respectively. These transistor photocouplers are housed in an SO4 packaged, measuring 2.6 mm × 7.0 mm × 2.1 mm and a 4-pin SO6 measuring 3.7 mm × 7.0 mm × 2.1 mm.

Photovoltaic Output

Toshiba offers two different photovoltaic output photocouplers. They employ a photodiode array as the primary method of coupling. Both perform similarly, offering short circuit current minimums (I_SC(min)) of 12 μA, and open voltage minimums (V_OC(min)) of 7 V. The main difference between the two is the internal control circuit, which allows the TLX9906 to turn off about 80% faster (0.2 ms vs. 1 ms). These two also come in a 4-pin SO6 measuring 3.7 mm x 7.0 mm x 2.1 mm.

MOSFET Output (Photorelays)

Photorelays are a great modern solution for replacing the traditional mechanical relay. The most significant benefit is the solid-state functionality, which allows for better longevity versus the traditional mechanical relay, which repeatedly moves a coil backward and forward. This lack of wear and tear is highly desirable in a product that is designed to have a long lifespan. Additionally, photorelays are functionally faster and less noisy. There is no bouncing or physical movement. Signals are clean and fast, two essential characteristics. The AEC-Q101 grade photorelay features an off-state voltage V_OFF maximum of 600 V and a maximum on-state current (I_ON) of 15 mA. This photorelay can also be found in the 4-pin SO6 package, which is substantially smaller than a traditional mechanical relay.

Diagram