2. Multifuse – MF (= Resettable fuse; = PPTC)
• The number of inductive loads (EPS, Veh. stabilization, e-pumps, …) will increase on
48V side requiring over current protection.
• In (partially) decentralized boardnet architecture, decentralized protection by MF can
lead to substantially reduction of space, wire weight, cost savings and increasing
flexibility significantly.
2
1 Transient Voltage Suppressor
2 Totally Integrated Surge Protector
Trends
TVS1/MF or TISP2/MF combination
• A MF in series and TVS or TISP (Die –only) parallel to load circuit all in one package for
circuit protection in hybrid boardnet:
• Short circuit between 12V and 48V
• Loss of common grounds
• Boardnet voltage lift due to loss of common ground and short circuit
• Load dump or resonance voltage step up
• Circuit protection in decentralized boardnet architectures
3. Transient protection
Regulations
Surges Pulses
ISO 7637-2
1 Supply disconnection from inductive loads – Power rail
protection
2a Sudden interrupt of currents in a device in parallel to device
under test due to inductance of wire harness – Power rail
protection
2b DC motors acting as generator after ignition is switch off –
Power rail protection
3a
3b
Switching processes – Power rail protection
4 Supply voltage drop by energizing starter-motor
5a
5b
Load-dump protection
ESD, IEC 61000-4-2 & ISO 10605 Dataline ESD protection
3
4. Wire harness protection
Reducing weight and costs
Decentralized
• Power routing in more direct way; less or no typical duplicated wiring
(In centralized architecture, wire length can easily exceed 10m for a load)
• Shorter and lighter gauge wire
• Reduction in terminals, contacts, switches, drive circuits
• Increases design/routing flexibility and assembly’s convenience
• Smaller main fuse box
• Requires distributed over-current protection (MF/PPTC devices)
4
Centralized
Decentralized
5. Possible protection to 48V boardnet failures modes
Example
Short circuit between 48V and 12V nets without connection to ground might destroy
complete 12V system (fuses might not blow (..not fast enough))
5
Circuit load
12V
48V
E-machine
Circuit loads typically 150mA to 300mA
6. Possible protection to 48V boardnet failures modes
Example
6
No component may lead to a transition into overvoltage level (54V) i.e. due to load dump or
resonance step up (requiring special measures at inductive loads)
Circuit load
12V
48V
E-machine
Circuit loads typically 150mA to 300mA
Circuit loadLiB
Protection device (MF and TVS in one package) able to handle (temporarily) the
excess energy (till board-CPU shuts down)
48V
54V
VDA320
U48max,high,limited
