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The diode in the circuit LM26480

Dmitriy Dmitriy
Prodigy 60 points
Other Parts Discussed in Thread: LM26480

Need to put a diode in the circuit  LM26480   SW to GND pins ? The diode is in the document AN-1800 Evaluation Kit for LM26480 - Dual DC/DC Buck   Regulators with Dual Low-Noise Linear Regulators   Figure 10  LM26480 Evaluation Board Schematic.   In  PCB  Evaluation Board no diode. In no other documentation diode. The diode is a classic scheme BUCK . Do I need a diode?

  • 0
    TI__Intellectual 1955 points

    Hi DV,

    One generally doesn't need the diode, but in some cases (this part is used in industrial as well as in portable handheld gadgets) where noise is a concern locally or on the bus, a low voltage Schottky ( 0.2V or so) can prevent the sw node from diving below ground potential by a -Vpn.  This can momentarily forward bias some internal junctions which can cause havoc to the chip (noisy at high peak current operations).  The diode also improves the design by a few % point when layout tightly/properly.  Most designs don't incorporate the didoe as noise was not an issue and/or when its cost matters.  The EVB was designed to address worst case operation where both bucks may be operating at max loading.  Hope this helps, 

    Kern