# What is actual maximum Current: BV1HD090FJ-CE2

Hello:

After going through the data sheet - it’s not clear. I’m looking to find out what is the maximum steady-state current with a 12VDC supply?
Assume a good optimized board layout with 2oz copper.

Thanks for any help, or references.

Gary

Greetings,

The overcurrent detection function may actuate at currents as low as 2.7A, so I’d consider that a ceiling on the maximum current one could rely on the part to carry. Thermal considerations may impact this, but that will be application dependent.

Well, a bad datasheet, maybe something lost in the translation. Can’t rely on it for anything that makes sense. They should outright state it, instead of some silliness range from 2.7 to 9.

Hi Gary,

One could make arguments both ways. If one intends to use overcurrent detection as an indication of an actual overcurrent event, you might want to know that it may trip over a quite broad range, and is, therefore, not something to be relied upon for downstream protection.

Regarding the actual operating conditions within which a device can be operated, looking at the maximum and minimums are the key specs, unlike the front page marketing blurbs one tends to see first.

For devices such as these, the max steady-state current depends on several factors, but it comes down to either the minimum overcurrent value or the combination of the maximum ambient air temperature you expect to encounter and the actual thermal impedance of your circuit board. Depending on the specifics of the latter specifications, both of which can vary greatly from one application to the next, the maximum current may be even less than the minimum overcurrent value of 2.7A.

To determine the maximum steady-state current, based on the maximum junction temperature, Tj, rather than the overcurrent spec, one has to consider the following:

The maximum junction temperature, Tj, of the BV1HD090FJ-CE2 is 150°C, so you must subtract your max expected operating temperature from 150°C to find the maximum increase in temperature allowed within the device. One then has to consider the thermal impedance of the circuit board and the maximum on-resistance of the device at the maximum junction temperature.

For example, assuming your circuit board has a thermal impedance of 86.9°C/W, as described in Note 3 on page 4 and 5 of the datasheet (2-layer board, 2oz copper, 114.3mm x 76.2mm), assuming you have a maximum operating temperature of 60°C (a relatively moderate assumption), and reading from the datasheet on page 7 that the maximum on-resistance of the device may be as high as 215mΩ, one can determine the maximum steady-state current.

With a max operating temperature of 60°C, the maximum Tj rise is:

Tj rise max = 150°C - 60°C = 90°C

With thermal impedance of 86.9°C/W, the maximum allowed power dissipation in the device while not exceeding Tj-max of 150°C is:

Pd-max = 90°C / 86.9°C/W = 1.036 W

With a maximum on-resistance of 215mΩ, the maximum current can be calculated as:

Imax = √(1.036 W / 0.215 Ω) = 2.195 A

So, even with a relatively low max ambient temperature of 60°C and a pretty decent thermal impedance of 86.9°C/W, the maximum current is only about 2.2A before exceeding Tjmax. So, because of all of the variables involved, it would be impractical for them to publish a hard number for max current, but this shows why it is important to actually calculate it for any given application.