Hi I'm using the chip for this application 
and I'm wondering why is it recommended to use a bidirectional TVS diode (D1) instead of unidirectional on the Vinput side.
Thanks
Hi Suphakorn,
In automotive applications, the device can be subjected to transient voltages as defined in standards like ISO 7637-2 and ISO 16750-2.
ISO 7637-2 is a negative voltage pulse which can go as low as -150V at the input. LM7480x-Q1 is rated for -65V and hence you will need a TVS in the negative direction to clamp the voltage seen by the IC to less than -65V.
A uni-directional negative TVS cannot be used alone and requires a diode to block forward current when input is positive. Hence, we use a bi-directional TVS.
Hi Praveen.
Thanks for the explanation. Just to clarify, if we don't expect a negative voltage on the input (other than transient negative voltages due to inductive loads), would a unidirectional TVS diode D1 (as shown below) be better choice than a bidirectional TVS protection in this case?
