Datasheet

DocID023280 Rev 3 15/28
ST1S15 Detailed description
7.6 Thermal protection
The device also has thermal shutdown protection, which is active when the junction
temperature reaches 125 °C. In this case both the high and low-side MOSFETs are turned
off.
Once the junction temperature goes back below 95 °C, the device resumes normal
operation.
7.7 Overcurrent protection
The overcurrent protection is used to limit the maximum inductor current. This current
flowing through the Pch of the power stage causes a voltage drop, across its RDSON, at the
switching node. A comparator compares the switching node voltage with a reference voltage
VR. To generate the VR voltage a current generator is used, which causes a drop across a
Pch of the same kind as the power stage. When the switching node voltage is lower than
VR, the comparator output goes high and the power Pch turns off.
7.8 Enable function
The ST1S15 features an enable function (pin 2 or B2). When the EN voltage is higher than
1.2 V the device is ON, and if it is lower than 0.4 V the device is OFF. In shutdown mode the
consumption is lower than 5 µA.
The EN pin does not have an internal pull-up, which means that the EN pin cannot be left
floating.
If the enable function is not used, the EN pin must be connected to V
IN
.