Self-resetting fuses for compact lithium polymer batteries

Called Model NX, they measure 2.8 x 9.8mm including two 2.8 x 2.5mm flat connecting tabs, one at each end. Height is just under 1mm.

“While our new Model NX Series has the same footprint as our Model NR series, it can carry 40% more current,” said Bourns v-p of products Brian Ahearne. “This is the result of numerous design advancements including the use of new high conductivity electrode materials. These features enable customers to shrink the size of their product and maintain an elevated level of over-temperature and over-current protection.”

Device resistance is 3mΩ max (1.2mΩ typ).

Disconnection is rated by temperature rather than current. The devices are available with four trip temperatures: 77, 82, 85 or 90°C – all ±5°C.

Resetting is at 40°C minimum and minimum holding voltage is 3V at 25°C for 1 minute. Max breaking current is 70A at 5V, with 100 cycle life.

Versions are available with or without bumps under the mounting tabs for welding.

Inside, “a high-rated corrosion-resistant bimetal mechanism delivers enhanced endurance in humid environments”, said Bourns – at 90% relative humidity and 60°C, the data sheet puts life at 1,500h.

On the subject of environment, the data sheet warns:” Avoid storage locations where there is a possibility of generating corrosive gas such as from salt breeze, chlorine, hydrogen sulphide, ammonium, sulfide-oxidation, hydrogen chloride or acetate.”

Over-temperature and over-current protection for lithium polymer and prismatic cells is one proposed application, in notebook PCs and tablets.

Find the NX series data sheet here