WPMDH1100601 / 171010601
MagI3C Power Module
VDRM – Variable Step Down Regulator Module
Overcurrent protection (OCP)
Current limit detection is carried out during the off-time by monitoring the current in the low-side MOSFET. Referring to the
Functional Block Diagram, when the high-side MOSFET is turned off, the inductor current flows through the load, the PGND
pin and the internal low-side MOSFET. If this current exceeds the ICL value, the current limit comparator disables the start of
the next on-time period. The inductor current is monitored during the off-time. As long as the inductor current exceeds ICL,
further on-time intervals will not occur. The next switching cycle will occur only if the FB input is less than 0.8V and the
inductor current has decreased below ICL (see figure below). The switching frequency is lower during current limited
operation due to the longer off-time.
Due to the current limitation the output voltage drops (see figure below). It should also be noted that the DC current limit
varies with the duty cycle, switching frequency, and temperature. At continuous overcurrent load the module junction
temperature increase until the overtemperature protection (OTP) is triggered.
4,0
3,0
6,0
5,0
4,0
3,0
2,0
1,0
0,0
Current limit
Output voltage drop
2,0
1,0
0,0
-1,0
-2,0
0
0,4
0,8
1,2
1,6
2
2,4
Time [ms]
Short circuit protection
In case of short circuit, the device detects the condition during the off-time monitoring the current in the low-side MOSFET.
As long as the current remains above ICL, the start of the next on-time is prevented. A new on-time cycle occurs when the
current falls below ICL (under short condition VOUT = 0 and VFB = 0, therefore the condition VFB<0.8V is always fulfilled). The
device alternates very short on-time and extended off-time (see figure below).
Inductor Current
overcurrent detected during tOFF
IL < ICL and VFB <0.8V
tON triggered
Time
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Würth Elektronik eiSos GmbH & Co. KG – Data Sheet Rev. 1.0
© September 2017
36/54
WURTH [ WURTH ELEKTRONIK GMBH & CO. KG, GERMANY. ]
