Datasheet unclear on absolute maximum ratings and active clamp voltage

[jeroen74]

At work we use a  IPS6044G which is a four channel intelligent protected high side switch. It also offers active clamping to demagnetise inductive loads quickly.

Now, I don't understand the following part: the datasheet states that the maximum output voltage is Vcc-35V. (In our application VCC=24V, so that equals to -11V). The specified clamping voltage is between 37 to 42V so during active clamping the voltage at Vout can be as low as 24-42 = -18V.  That's 7 volts more then is allowed 

In an actual test I measured -15.8V which basically confirms the clamping voltage ~39V.

What use is this active clamp circuitry if it consistently violates the absolute maximum rating? Or am I misinterpreting the specification?

I asked IRF about it; their answer is that I should use another series as this one is not meant for 24V and they referred to appnote #1117 which is not really helpful on this particular issue.

I looked at other high side switches like from Infineon and ST and they don't mention an absolute maximum rating at all for the output, just a clamping voltage...

[Rufus]

Now, I don't understand the following part: the datasheet states that the maximum output voltage is Vcc-35V.

The abs min Vout and Voffset ratings are a little confusing but I think they mean the maximum voltage where the clamping mechanism will not turn on. Exceeding that voltage may activate the clamp and you then have current and power dissipation limits.

It is common to see specifications for input pin voltage of say VCC + 0.3v and an input pin maximum current of say 10mA while a voltage of greater than VCC + 0.3v would be required to get any pin current.

If you are actually using the clamps to absorb inductor stored energy be careful because they don't have much capability. That part has a plot of maximum load inductance against current and it is only 2mH at 3A for example.

[jeroen74]

Yes, I thought something like that too The active clamp controls the FET to get a controlled clamp voltage but this is only active when the driver turns off, not during other situations.

I really would like to IRF to state this a little more clearly in the datasheet. Let's see what their support department has to say on this, as I emailed them back that I'm still a little confused

The biggest inductive load we switch only draws a mere 24mA at 24V. That's not even in the graph, but extrapolating from it, the inductance must be a couple of Henries before it becomes a problem.

[dannyf]

the maximum output voltage is Vcc-35V.

That doesn't make a whole lot of sense for the maximum output. Minimum output? Maybe.

[jeroen74]

Oh well.... yes....

Maximum output voltage: min= Vcc - 35V,  max=Vcc + 0.3V