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ISL94202 Load Monitoring Power-On Reset

errolmurray

Hi,

I've built a system around the ISL94202 that has an integrated battery pack (the cells/BMS circuit are not removeable once assembled). The first time the device is assembled it works okay because the batteries are connected to the BMS prior to any load being attached.

However I'd ideally like to be able to put the device into a "Powerdown State" for long term storage. The problem that I have is that the load is not removeable so after reconnecting the charger the device is unable to transition from "Power-On Reset" to "Normal Operating Mode".

Is there any way to configure the ISL94202 to ignore the presence of a load for this state transition?

Alternatively I could place a FET in the discharge path that is controlled by the charger, to disconnect the load while a charger is present. Then the charger would just need to be connected long enough for the ISL94202 to reach "Normal Operating Mode", but this would require additional components.

Thanks,

Errol

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  • 0

    Hi, 

    I will check with concern team and come back to you

    Thanks 

    AB 

  • 0 in reply to AB_RENESAS

    Hi,

    It's been close to a month, just following up to see if there's any answer to this?

    Thanks,

    Errol

  • 0 in reply to errolmurray

    Hi, 

    Please go through this document for sleep and power down issues ISL94202 Sleep Mode Requirements (renesas.com)

    Because the device is designed to be autonomous it has a safety feature built in which prevents the device from automatically enabling the FETs if it wakes from power down mode and detects a load.  Some serious faults can send the device to power down, for this reason the FETs are off if the load is detected on exit from power down.

    If the LDMON input can be held above the threshold detailed in the document it will not detect the load and the FETs will be enabled.  The FET you suggests could be used for this instead of disconnecting the load, whichever you chooses depends on what works best with the type of load.

    If a load is detected on exit from power down the device does wake up into normal mode, but it keeps the FETs off.  Is there an MCU that communicates with the ISL94202?  If so you can put the device into MCU control, enable the FETs then disable MCU control then the device will continue to work autonomously.

    Thanks 

    AB

  • 0 in reply to AB_RENESAS

    Hi AB,

    There is an external MCU that communicates with the ISL94202 but the issue is that the MCU is powered from the batteries. So when the device wakes into normal mode but keeps the FETS off, it also keeps the MCU off and prevents it from overriding the FET control.

    I had another idea, if I change the 499 resistor attached to the LDMON pin, would that effectively alter the load required to trigger a load detect?

    My device has a phased power on, so the MCU switches on and then it sequentially turns on everything else in the system, if I could alter the load detect threshold so that the MCU on its own doesn't trigger a load detect then the system should work fine.

    The device would power up the MCU and no load would be detected. Then the MCU could wait until the initialisation was complete before turning on the other ICs - at which time the ISL94202 would detect a load and work correctly.

    Is there any issue with that approach?

    Thanks,

    Errol

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  • 0 in reply to AB_RENESAS

    Hi AB,

    There is an external MCU that communicates with the ISL94202 but the issue is that the MCU is powered from the batteries. So when the device wakes into normal mode but keeps the FETS off, it also keeps the MCU off and prevents it from overriding the FET control.

    I had another idea, if I change the 499 resistor attached to the LDMON pin, would that effectively alter the load required to trigger a load detect?

    My device has a phased power on, so the MCU switches on and then it sequentially turns on everything else in the system, if I could alter the load detect threshold so that the MCU on its own doesn't trigger a load detect then the system should work fine.

    The device would power up the MCU and no load would be detected. Then the MCU could wait until the initialisation was complete before turning on the other ICs - at which time the ISL94202 would detect a load and work correctly.

    Is there any issue with that approach?

    Thanks,

    Errol

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