When a clamped alternator is mandated by the automotive manufacturer, “Test B—with centralized load dump suppression” applies. Figure 5 shows the clamped waveform from Test B in ISO 16750-2. Although ISO 16750-2 specifies a 35V maximum voltage for this clamped scenario, be aware that many manufacturers deviate from ISO 16750-2 by providing their own maximum voltage specification.
Also, be aware that when load dump was part of ISO 7637-2, only one pulse was specified, but when the load dump specification moved to ISO 16750-2 in 2011, the minimum test requirements increased to include multiple pulses with a one minute interval between pulses.
TVS Protection Problems
The internal resistance, Ri, of the alternator in both Test A and Test B is specified to be between 0.5Ω and 4Ω in ISO 16750-2. This limits the maximum energy that is delivered to protection circuits.