Can you explain the over-current protection (OCP) of the MP6519 when the current is flowing larger than 200% of the full-scale setting value? How do you calculate this current value? Do they monitor peak or average value?
The 200% latch OCP monitors the current through each MOSFET directly measuring peak value (not average). The full-scale current will depend on the current sense used. Assume default value of 40mohm Rsense. The full scale MOSFET current = Vref_full / 0.04 where Vref_full = 0.240/Riset. You can calculated the latch current = 2 Vref_full / 0.04. If this value is longer for longer than a certain blanking time, then the IC will latch off.
If the high-side MOSFET hits over-current, the high-side MOSFET is turned off immediately and the Fault pin is driven low. At the same time, the two low-side MOSFETs are turned on for several milliseconds and then the two low-side MOSFETs are turned off and IC latches off. The reverse will happen if the low-side MOSFET hits over-current where the low-side MOSFET is turned off immediately and the Fault pin is driven low. And at the same time the high-side MOSFETs are turned on for several milliseconds and then the high-side MOSFETs are turned off and IC latches off.
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If the high-side MOSFET hits over-current
This is unclear to me. Does “over-current” mean 200% at any time? Or does it mean 150% on two cycles or does it mean simply above 100% of the full-scale current? It is always useful to use consistent terminology. The data sheet uses this same phrase and so is also unclear.
It is also unclear to me how the current would exceed 100% of full-scale current since the current is supposed to be limited or controlled.
I would also ask what “Hiccup over-current threshold” means? I see this in the data sheet on two specification lines, but nowhere is “hiccup” explained.
Just below these on page 6 of the data sheet there is the “Latch-off over-current threshold” which is not discussed in the Over-Current Protection section on page 15. Is 13 amps an absolute threshold in addition to the 200% of full-scale Iset value?
Hi,
Over-current has different meanings because of the different current limit settings. If ISET is left floating, current limit is defined in the datasheet as 13A:
Current higher than this will cause the device to enter latch-off protection. This limit can be lowered using a resistor on the ISET pin.
There are multiple ways the device can enter OCP, if the current exceeds 150% of the current limit setting for 2 cycles, it will stop switching. If the device exceeds 200% current limit setting, the device will latch-off. These are both over current conditions, with different types of protections.
Over-current essentially means the device is drawing more current than it is set to or capable of providing. This can happen from a variety of situations, including a short circuit, ground issue, or accidental overload. Even though the device has a current limit, over-currents conditions can still happen, so it is important to have this protection.
Thanks,
Brendan Schoemehl
Field Applications Engineer
Monolithic Power Systems | MPS Now
Hi Gnuarm,
The hiccup protection threshold should be the 150% full-scale value considering the description of that protection explains the device will stop switching and reset power under that condition.
No, the Latch-off over-current threshold is discussed on page 15. Consider it the 200% of the full-scale value under the condition RIset = float. I would call this the absolute threshold as well.
Thanks,
Brendan Schoemehl
Field Applications Engineer
Monolithic Power Systems | MPS Now