I have an automotive (24 V system) circuit consuming 140-220 mA depending the supply voltage (19-30 V). To fullfill ISO7637 standard it must last pulse 5 (LOAD DUMP) which is 200 ms pulse going to 141 V at 10 ms and then going down to about 40 V, test generators output impedance is 3,3 oms. This pulse simulates situation as battery is disconnected at full alternator speed.
The traditional solvation is to use large series resistor combined with large varistor or transient voltage suppressor. I don't want to use varistors because they tend to 'age' and finally short themselves. Because of relatively big current consumption the impedance of series resistor must be quite low (about 4,7 ohms) and then TVS must be high power rated (read: pricey)! 1.5KEs aren't enough, their 1500 W is rated at 1 ms pulse.
Normally all automotive application notes and smart components are for 12 V systems..so
..any suggestions welcome
[sig][/sig]
The traditional solvation is to use large series resistor combined with large varistor or transient voltage suppressor. I don't want to use varistors because they tend to 'age' and finally short themselves. Because of relatively big current consumption the impedance of series resistor must be quite low (about 4,7 ohms) and then TVS must be high power rated (read: pricey)! 1.5KEs aren't enough, their 1500 W is rated at 1 ms pulse.
Normally all automotive application notes and smart components are for 12 V systems..so
..any suggestions welcome
[sig][/sig]
