Why a New 80 V Resistor-Equipped Transistor is Relevant for EV System Design - News

The 48 V power supply used in most automotive systems imposes unique constraints on the components that design engineers choose to integrate.

On the one hand, these systems require transistors that can handle higher currents, higher input voltages, and (usually) lower R.

Values. However, even transistors designed to handle these voltages can fail under certain conditions, the high transient spikes common in automotive systems. 

The latest version of Nexperia aims to alleviate this problem:

. These RETs, also known as digital transistors, are designed to help adapt to outdated automotive designs and provide sufficient voltage margin for the component to meet the needs of EV boards. 

It has a built-in bias network, which is composed of a base resistor and a base-emitter resistor in series.

The input resistor is used to convert the input voltage into current, and the base-emitter resistor helps to absorb leakage current and prevent malfunction due to noise. The working principle of BJT is similar to that of normal BJT, and the saturation of its VBE is about 0.7V. This means that when the input current is small (the voltage across R1 is small), most of the current will pass through R2 to ground.

When the input current is large, most of the current will flow to the base of the transistor, and only ~0.7/R2 ampere current flows to the ground. Therefore, this setting ensures safe operation and protection from noise (assuming they are small voltages). 

In most cases, RET acts as a switch. 

Although RET can ensure safe operation, designers can also design only a discrete transistor with two discrete resistors and achieve the same result. 

RET is popular because all components are integrated in one package, which saves board space and cost. Although saving board space is always an important consideration for designers, electric vehicle engineers may be particularly concerned about this goal, even if the system is as lightweight as possible.

However, the downside is that 48 V RET tends to fail when there is a large voltage spike. As mentioned earlier, this setting is designed to prevent malfunctions due to small noise currents. When a large voltage fluctuation occurs, the input base current is approximately (Vfluctuation-0.7V)/R1 ampere. Therefore, when these fluctuations are too large, the transistor may encounter excessive base current and burn out. 

It is worth noting that in EV systems, a very popular and widely used transistor substitute is high-power MOSFET, such as SiC FET or other 48 V FET. 

Adopt a new design designed to handle 80 V standard operation,

No need to worry about failures due to voltage spikes. Nexperia claims that this is the industry's first 80 V RET, which makes the news even more important, as this may be the first instance where RET has become truly usable in an EV system.

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