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Original question:

TM4C1294 battery drain help

TM4C1294NCPDT: Battery Drain Issue

palanie
Prodigy 50 points

Part Number: TM4C1294NCPDT

I use TM4C1294NCPDT in our design. MCU VBAT is provided with 3.6v 60mA Battery with series Diodes. When ever there was low battery condition, the current taken by VBAT is around 30mA when the board is powered off, making the battery to further drained. Once I forcefully make this VBAT bin with 3V external source, this issue becomes ok. Any possible cause for this issue. Thanks in advance for your support. Regards Palaniappan

  • 0
    TI__Guru 72500 points
    Have you set the BATWKEN bit (bit 9 of HIBCTL)? This causes the device to come out of hibernation mode when the battery level drops the low battery threshold.
  • 0 in reply to Bob Crosby
    Prodigy 50 points
    Thanks for your reply. Our functionality does not need Hibernation mode and waking up from Hibernation mode. Hibernation module is used only to activate RTC. When the VDD is off, the system need not wakeup. System should function only when VDD is supplied to MCU. When VDD is off, RTC should run. When VDD is oFF and VBAT is going down, then MCU enters into a state where it takes current from VBAT around 30mA. VDD is OFF only. We don't need to run the MCU when VBAT is low. MCU should not draw current from VBAT (when VDD is off) and MCU need not wakeup or operate at that time. To Bring the MCU to normal condition, we need to apply 3V (external power source - not a battery) for a moment and then the MCU is recovered to normal state (where no current is taken from VBAT when VDD is off). Thanks for your support
  • 0 in reply to palanie
    Guru 56218 points

    palanie said:
    When VDD is off, RTC should run. When VDD is oFF and VBAT is going down, then MCU enters into a state where it takes current from VBAT around 30mA.

    Wonder if you don't put peripherals to sleep when or if clock gating is enabled current flows from VBAT into VDD rail as VDD lowers below VBAT. The RTC is only time clock for ANSI time/date keeping?