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LM66100: Review Request

Part Number: LM66100
Other Parts Discussed in Thread: TPS2116

Please provide feedback on the attached schematic for the most efficient/lowest power configuration. The product will use one battery pack with a second one as an option added by a customer. The battery packs are identical with a 2.0V-3.6V operating range. Maximum peak pulse current used by the circuit is .2A with typical sleep current of 10uA, and operating current of 30mA.

4520.Power.pdf

  • Hi Alan,

    LM66100 is not built to handle any sort of load sharing situation. If both battery packs are populated, this is an unsupported load sharing topology.

    The LM66100 is built to OR between two inputs as shown in Figure 15 and Figure 17 in the datasheet. I recommend changing the setup to be OR-ing or to externally block off both packs being connected at the same time.

    Thanks,

    Shreyas

  • Hi Shreyas, thank you for the response. The data sheet does mention that when both inputs are at the same voltage there is a risk of turning off. Given your feedback, it's clear that this part is not meant for sharing. Do you have a suitable part that would work with a low Iq? 

  • Hi Alan,

    Is a sharing system required? We do not have devices that can effectively current share although it is possible to do so with eFuses as mentioned in this application note: https://www.ti.com/lit/an/slva836/slva836.pdf 

    I would recommend using a PowerMUX like TPS2116 that autoswitches between two sources depending on voltage levels or a user set priority. This device has low Iq.

    Thanks,

    Shreyas

  • The TPS2116 comes close but the switch over does not really work like two diodes in parallel. With two diodes in parallel they do not equally share current but there is no 'switch over'. The problem with diodes is that they have a large voltage drop and are inefficient. All I really need is a part with low Iq, integrated FET, low Rds On that can be paralleled and act like a diode from a switching standpoint.

  • Hi Alan,

    The major risk and why LM66100 cannot work here is the reverse current protection of our devices work only after a small voltage difference is noticed between VOUT and VIN. This means that some reverse current has to flow to generate this voltage. At low R_on, this voltage generation will take (in the case of LM661000 around 0.5A. As such, if there is a slight voltage difference(if they are not perfectly balanced) from the batteries, it is possible that long low current reverse flows could take place.

    At this time, we do not have a low Iq current sharing switch. Thank you for sharing details about your system.

    Shreyas