TM4C1294NCPDT: RTC Module taking high current (around 60mA)

Hello Palanie,

I feel I am missing more information/context, some questions which would help better understand this issue:

1) Was the device working fine with low current draw for a period of time?
2) Is this an isolated failure from a sizable batch or something that occurred on a development prototype?
3) You mention the RTC, how is the device being used? Can you share the code to configure RTC, Hibernation, etc?
4) Do you have any debug capability to read device registers?
5) Did you develop anything on a LaunchPad where we can try and test your code and make measurements on our end?

Hello Ralph Jacobi

Thanks for your reply.

1. Yes the device was working with low current in VBAT for few weeks. Since the 3.6V battery charging circuit is simple there is a possibility of overcharging and Voltage at VBAT might have touched the upper limit of 3.6V in this few weeks time.

2. one or two failures from few hundred products that are running in Field

3. Please find below the RTC initialization code. The conditional macro "RTC_HIBERNATE_LOWBAT_ENABLED" is disabled in the current implementation.

void rtc_init_devices(void )
{ 
 ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_HIBERNATE);
 HibernateEnableExpClk(g_SysClock);
 HibernateClockConfig(HIBERNATE_OSC_LOWDRIVE);
 HibernateRTCEnable();
    HibernateCounterMode(HIBERNATE_COUNTER_24HR);     // Configure the hibernate module counter to 24-hour calendar mode.
 
 #if (RTC_HIBERNATE_LOWBAT_ENABLED)        // Should be enabled to avoid battery drain condition.
 HibernateLowBatSet(HIBERNATE_LOW_BAT_ABORT);
 #endif
 
}

4. Yes we have Debug Capability and we can use Ulink Debugger to read the registers.

5. Not in the lauchpad. It is our proprietary hardware.

Thanks.

Palani

Hello Palanie,

Okay, so am I right to understand that there is no LDO or anything to limit the input voltage to the TM4C MCU?

If you can read registers, I would recommend trying to read out the Hibernation Interrupt Status registers to see if any interrupts are sitting which may have kicked the device out of hibernation mode. We'll have to smart about analyzing this though as the debug process likely will kick the device out of hibernation mode so we will have to be sure what is seen wasn't triggered because of the debugger. I suspect it would show up as a Reset interrupt.

If you have more than 1 failing board, perhaps you can also try re-flashing the firmware and see if the current goes back down? If so, then we'd know the root cause is a software issue.

Hello Ralph Jacobi

No. I am still having the problem. Not able to locate the root cause. Can we interact with any technical person directly near by our location.

Best Regards

Palaniappan

Hello Palanie,

I do not have any way to loop you with a field team, if you don't know anyone then you may need to ask your colleagues. I have no visibility as to who would be able to support you at your location.

I had asked some prior questions above, have you done any testing regarding if the boards can be recovered when the firmware is reflashed?