TMC248-LA DATASHEET (Rev. 1.01 / 2013-MAR-26)
26
9.3 Overvoltage Protection and ENN Pin Behavior
Many suitable power MOSFETs are 30 V types. The TMC248 allows protecting the MOSFETs up to 40 V
supply voltage while they are switched off. During disable conditions the circuit switches off all
output power transistors and goes into a low current shutdown mode. All register contents are
cleared to 0, and all status flags are cleared.
The circuit in this condition can stand a higher voltage. The voltage is not limited by the maximum
power MOSFET voltage any more.
The enable pin ENN provides a fixed threshold of ½ VCC to allow a simple overvoltage protection up
to 40V using an external voltage divider (see schematic).
+VM
For switch off at 26 - 29V:
at VCC=5V: R1=100K; R2=10K
at VCC=3.3V: R1=160K; R2=10K
ENN
µC-Port (opt.)
low=Enable,
high=Disable
Figure 9.1 Overvoltage protection
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