ISL94202 - /SD line - is it useful when no MCU present?

Hi Folks,

I have a 8S4P LiFePO4 pack being controlled by the ISL94202 but I have run into an issue that doesn't make sense to me.  Our BMS board doesn't use a MCU so it's dependent on the 94202 chip.  Currently we have a LED controlled by the /SD line.  If there's an error the LED lights and let's the end user know something is wrong.

The issue is why does the /SD line go active when the unit goes into SLEEP mode?  We need the chip go go into a low current state to keep the battery from going low when the unit isn't being used.  But since the /SD line is active during SLEEP mode we can't use that to control the error LED.

Is there any way to be able to indicate to the end user that an error has occurred but not during SLEEP mode?

Thanks,

Richard

  • hmm... not sure. We'll have someone look into this one. Sorry for delay <we had a few people out on vacation>. BR JE_REN

  • Hi Richard,

    I checked with the factory apps engineer who is responsible for this part. Here is his response:

    The purpose of the SD pin is to provide an alert to the user that the power FETs have been turned off by the device.

    The PSD pin can be linked to fatal faults such as OVLO, UVLO and DVCF and be used to drive an external circuit that alerts the user to these faults, and/or blows a fuse. 

    If either pin is used to drive an external circuit care must be taken to prevent complete discharge of the cells.

    Best regards, Cindy