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TPS2640: Parallell TVS diode not described in datasheet

Part Number: TPS2640
Other Parts Discussed in Thread: TPS2660

Hi, regarding supression of transients: Figure 10.1 and Figure 11-1 in datasheet describes a TVS diode in parallell to the efuse (D2) - between Vin and Vout. This diode is not described for TPS26600, nether in datasheet or the related application note, SLVA833D. What purpose does this paralell TVS serve? Surge transients on input will be managed by the large SMC diode connected to input terminals. Remaning transients should be absorbed by capacitors. What is the purpose of this parallell TVS diode? What kind of load can be expected - i.e how to select a proper part? 

  • Hi Jan,

    Welcome to E2E!

    The IN-OUT rating of TPS2640 is limited to 45V max. During surge event, the output capacitor holds the 24V and input swings towards -42V resulting in a voltage of 24V+42V= 66V across TPS2640 which can violate the rating. To protect the device, TVS diode in parallell to the efuse is suggested. 

    However, we recommend to use higher voltage device TPS2660 so that we don't need these additional diodes.

    Best Regards,

    Rakesh

  • Thank you, that makes perfect sense. I had not considered that case. Unfortunately TPS2660 is very difficult to procure these days, so we need the option for TPS2640.