![]() Prior to 2011, load dump was initially defined as 5a and 5b pulses in the ISO 7637 standard entitled "Road vehicles-Electrical disturbances from conduction and coupling" and was considered an electromagnetic compatibility (EMC) specification, which included transients related to supply quality. Standards often evolve to meet the design challenges of today's technology. Output voltage of an alternator during a load-dump event showing nominal battery voltage (V B). The amount of energy dumped to the load depends on the internal resistance (R i) of the source, as shown in Figure 2.įigure 3. The VP can be as high as 202V and may take up to 350ms to decay. Second is the pulse duration (t d), which depends on the time constant of the field excitation circuit and V P, as shown in Figure 3. First is the pulse amplitude (V P), which depends on the alternator speed and the level of the alternator's field excitation at the time when the battery is disconnected. To understand how the load dump affects the downstream subsystem, we need to understand the components of the load dump. This can happen when a discharged battery loses connectivity while the alternator is generating charging current and other loads are connected to the alternator circuit, as shown in Figure 2. In automotive systems, a load-dump transient occurs when an alternator is delivering current to a battery and the battery is abruptly removed. Now we will look at what causes a load dump and how it affects the subsystems in this design. Within the automotive system, the downstream subsystem contains the most sensitive components, so the challenge for system designer is to reliably regulate the automotive battery voltage to power these sensors and processors within the ECUs. A common power architecture inside an automotive system consists of a battery, alternator, protection system block, DC-DC converters, and downstream subsystems that include LDOs and different functional ECUs, as shown in Figure 1. Lightweight vehicles like cars typically use a 12V battery, whereas heavyweight vehicles like trucks, cranes, and tractors typically use 24V batteries. To understand how to protect a subsystem from a load-dump pulse, we must first understand the architecture inside an automotive system.Īutomotive vehicles can be divided into two classes: lightweight and heavyweight vehicles. Power architecture inside an automotive system. ![]() These test pulses were previously described in ISO 7637-2 as 5a and 5b, respectively.įigure 1. In this application note, we show how to protect your downstream subsystem from a load-dump pulse in a 24V systems as per the ISO 16750-2 specification for test A (without centralized load-dump suppression) and test B (with centralized load-dump suppression) pulses. As passenger safety is the primary objective of advanced driver-assistance systems (ADAS), increasing numbers of auto manufacturers are adding more safety and reliability ICs to their automotive systems.Ī key component of system safety and reliability includes a robust power management and subsystems protection design, which prevents downstream damage from high-energy transient pulses. Semiconductor components are transforming the automotive industry by adding a wide-range of innovations in self-driving vehicles, passenger safety, and vehicle-to-vehicle communication.
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