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Original question:

CC2340R5-Q1: Stand by power policy in CC2340r5 low power SDK sample application , does not actually put the MCU in standby...

CC2340R5-Q1: How can we ensure the MCU is in standby mode in application firmware

ilanchezhian Thingalkodi
Intellectual 350 points
Part Number: CC2340R5-Q1
Other Parts Discussed in Thread: CC2340R5

Hi  Team , 

  1. Current Consumption Issue:
    • We observe even with BLE advertisement disabled, your MCU still consumes 4 mA to 6 mA of current.
    • Our user task sleeps every 90 seconds, and during this time, the Hall sensor (connected via SPI) is put into sleep mode, drawing 1.2 μA as specified in the datasheet.
  2. Expected Behavior:
    • Since BLE advertisement is disabled, we expect the BLE task to also sleep.
    • Ideally, the MCU should be in standby mode during the 90-second sleep interval, drawing around 1.1 μA (as mentioned in the datasheet).
  3. Observations:
    • However, we are noticing current pulses occurring approximately every 250 ms.
    • These pulses are unexpected and seem to prevent the MCU from entering the desired low-power standby mode.

 Our code flow is as below, 

1. Initialization of MCU,

2. Start the BLE task 

3. Start of user task 

User task code flow, 

1. Disable the advertisement  

2. Put the Hall sensor (connected via SPI) to sleep mode  ( we see 1.2uA as dictated by datasheet)  

Do for ever loop 

{

1. Wake up the Hall sensor 

2. Do Sensor read over SPI 

3.  Put the Hall sensor to sleep mode 

sleep(90)

} 

      

With Regards

Ilanchezhian T 

  • 0
    TI__Mastermind 42100 points

    Hi Ilanchezhian T,

    In the CC2340R5, the power manager takes care of placing the device in the lowest power mode possible, depending on the peripherals active. From a BLE perspective, if there is no active connection, advertisements, or scanning, then the device BLE stack should allow the device to go into standby. However, the peripherals may keep a device active or idle depending on how they are configured.

    To me, those pulses look like recharge pulses which are pulses the device does if its it in sleep for too long. I recommend reading over the following app note for more information on what these pulses are and how they can be minimized:

    https://www.ti.com/lit/swra478

    Please zoom into one of these pulses to see the profile of the current. If it matches the VDDR pulse outlined in the app-note (in shape and magnitude), then this is the likely cause. The app note provides some information on how to minimize these. These pulses are expected if the device is in standby or sleep for long periods of time.

    The power management table is shown below (from the CC2340R5 datasheet):

    Here we can see that the only periphreals that may remain on/active when the device enters standby are the IOC, BATMON, RTC, and LPCOMP. Any other peripheral should be put to sleep or disabled (and made active on wakeup).

    Please ensure that the SPI driver is not holding the device in idle.

    I also see that you are using a custom board, to get a baseline, I would suggest running the empty project on the board to get a baseline measurement.

    Best Regards,

    Jan