Datasheet

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Würth Elektronik eiSos GmbH & Co. KG - Data Sheet - REV 1.0
16/25
WPMDM1500602/ 171050601
MagI³C Power Module
VDRM - Variable Step Down Regulator Module
PROTECTIVE FEATURES
Output Over-voltage protection (OVP)
The voltage at FB is compared to a 0.92V internal reference. If FB rises above 0.92V the on-time is immediately
terminated. This condition is known as over-voltage protection (OVP). It can occur if the input voltage is increased
very suddenly or if the output load is decreased very suddenly. Once OVP is activated, the top MOSFET on-times will
be inhibited until the condition clears. Additionally, the synchronous MOSFET will remain on until inductor current falls
to zero.
Over current protection (OCP)
Current limit detection is carried out during the off-time by monitoring the current in the synchronous MOSFET.
Referring to the Functional Block Diagram, when the top MOSFET is turned off, the inductor current flows through the
load, the PGND pin and the internal synchronous MOSFET. If this current exceeds the I
CL
value, the current limit
comparator disables the start of the next on-time period. The next switching cycle will occur only if the FB input is less
than 0.8V and the inductor current has decreased below I
CL
. Inductor current is monitored during the period of time
the synchronous MOSFET is conducting. So long as inductor current exceeds I
CL
, further on-time intervals for the top
MOSFET will not occur. Switching frequency is lower during current limit due to the longer off-time. It should also be
noted that DC current limit varies with duty cycle, switching frequency, and temperature.
Over temperature protection (OTP)
The junction temperature of the MagI³C power module should not be allowed to exceed its maximum ratings. Thermal
protection is implemented by an internal Thermal Shutdown circuit which activates at 165°C (typ) causing the device
to enter a low power standby state. In this state the main MOSFET remains off causing V
OUT
to fall, and additionally
the C
SS
capacitor is discharged to ground. Thermal protection helps prevent catastrophic failures for accidental
device overheating. When the junction temperature falls back below 145°C (typ Hyst = 20°C) the SS pin is released,
V
OUT
rises smoothly, and normal operation resumes.
Applications requiring maximum output current especially those at high input voltage may require additional derating
at elevated temperatures.
Zero coil current detection (ZCCT)
The current of the lower (synchronous) MOSFET is monitored by a zero coil current detection circuit which inhibits
the synchronous MOSFET when its current reaches zero until the next on-time. This circuit enables the DCM
operating mode, which improves efficiency at light loads.
Output under-voltage protection (UVP)
The MagI³C power module will properly start up into a pre-biased output. This startup situation is common in multiple
rail logic applications where current paths may exist between different power rails during the startup sequence. The
pre-bias level of the output voltage must be less than the input UVLO set point. This will prevent the output pre-bias
from enabling the regulator through the high side MOSFET body diode.