Datasheet

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© May 2016
Würth Elektronik eiSos GmbH & Co. KG - Data Sheet - REV 1.0
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WPMDU1251501 / 171021501
MagI³C Power Module
VDRM - Variable Step Down Regulator Module
PROTECTIVE FEATURES
Over current protection (OCP)
For protection against load faults, the MagI³C Power Module incorporates cycle-by-cycle current limiting. During an
overcurrent condition the output current is limited and the output voltage is reduced, as shown in Figure 14. As the
output voltage drops more than 8% below the set point, the PG signal is pulled low. If the output voltage drops more
than 25% during an overcurrent condition, the module skips switching cycles to reduce power dissipation within the
device. When the overcurrent condition is removed, the output voltage returns to the established voltage. The MagI³C
Power Module is not designed to endure a sustained short circuit condition. The use of an output fuse, voltage
supervisor circuit, or other overcurrent protection circuit is recommended. A recommended overcurrent protection circuit
is shown in Figure 15. This circuit uses the PG signal as an indication of an overcurrent condition. As PG remains low,
the TLC555 timer operates as a low frequency oscillator, driving the EN/UVLO pin low for approximately 400ms, halting
the power conversion of the device. After the inhibit interval, the EN/UVLO pin is released and the MagI³C Power
Module restarts. If the overcurrent condition is removed, the PG signal goes high, resetting the oscillator and power
conversion resumes, otherwise the inhibit cycle repeats.
2V/Div
5A/Div
5V/Div
V
PWRGD
100µs/Div
28D
I
OUT
V
OUT
CONT
DIS
TLC555
OUT
RST
GND
THRS
TRIG
VDD
1µF
47.5kΩ
100kΩ
100kΩ
475kΩ
3.3V/5V
3.3V/5V
To EN/UVLO
Pin 27
From PWRGD
Pin 35
BSS138
BSS138
Figure 14. Overcurrent Limiting Figure 15. Over-Current Protection Circuit
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 180°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 165° the SS pin is released, V
OUT
rises smoothly, and functional operation
resumes. Please note that an operation of the junction above 125°C is not recommended.
Applications requiring maximum output current especially those at high input voltage may require additional derating at
elevated temperatures