Texas Instruments LM74670-SQEVM, User Manual, Page: 6 / 19

Time (100 µs/DIV)
V
OUT
(10 V/DIV, 12 V to 0 V)
V
IN
(10 V/DIV, 12 V to -20 V)
Gate Drive (10 V/DIV)
Operation
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3 Operation
3.1 Reverse Polarity Protection
A dynamic voltage pulse from +12V to -20V is applied at the VBAT_1 input of the LM74670-Q1-SQEVM.
Figure 3 shows when the input voltage (yellow) drops down to -20V, the output voltage (blue) does not go
negative, and therefore, the load is protected from dynamic reverse pulses at the input. The LM74670-Q1
reacts the negative voltage surge within 2
μ sec and shuts down the MOSFET by pulling the gate voltage to
zero (green). The output slowly decays due to the large output capacitors and increased time constant.
Figure 3. Response to Reverse Polarity 12V to -20V
6 List of Tables SNVU494 – October 2015
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