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TPS7A85: RCP scheme of LDO devices

Part Number: TPS7A85
Other Parts Discussed in Thread: TPS74401, LP38798, TPS7B4254-Q1, TPS709-Q1

Hello,

May I have some questions regarding RCP scheme of LDO devices? In 8.1.19 in TPS7A85 datasheet, it suggests to add a schottky diode to prevent the reverse current damage. 

(1) I notice some other devices do not include this suggestion in the datasheet - TPS74401 for instance. I wonder if those devices have another protection scheme integrated in the IC. Maybe the schottky diode is integrated in the package?

(2) As the concern of reverse current comes from its inherent body diode structure from OUT to IN, I believe LDO devices with P-FET such as LP38798 do not have concern regarding the reverse current. There would be the body diode from IN to OUT for P-channel pass-FET. Is my understanding correct?  

  • Hi Ella,

    Some devices do have integrated reverse current protection, but if they do it will be specified clearly in the datasheet. LP38798 does not have integrated reverse current protection, and this is also apparent when you look at the abs max table for VOUT, which is specified as VIN + 0.3V. Going higher than this will be close to a diode drop, and the body diode will begin conducting and can damage the device. 

    If there is not reverse current protection specified in the datasheet, you can assume that the body of the pass FET is connected to the source (which is at VIN), which eliminates the body diode from IN to OUT, but it will be the case that the OUT to IN body diode is still present and can conduct under a reverse-bias condition. If there is integrated reverse current protection, it may not be the case that the body of the pass FET is connected to the source because it can be tied elsewhere to aid in preventing reverse current. 

    Regards,

    Nick

  • Hi Nick,

    Thank you for comment. Could you help me to find some devices that have integrated reverse current protection for examples? 

  • Hi Ella,

    TPS709-Q1 and TPS7B4254-Q1 both have reverse current protection. If you use this parametric search tool, on the left side under Features you can filter all LDOs for only ones that have this feature. 

    Regards,

    Nick