SWRZ136B December   2023  – July 2025 CC2340R5-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Advisories Matrix
  5. 2Nomenclature, Package Symbolization, and Revision Identification
    1. 2.1 Device and Development Support-Tool Nomenclature
    2. 2.2 Devices Supported
    3. 2.3 Package Symbolization and Revision Identification
  6. 3Advisories
    1. 3.1  SPI_04
    2. 3.2  ADC_08
    3. 3.3  ADC_09
    4. 3.4  BATMON_01
    5. 3.5  BATMON_02
    6. 3.6  CKM_01
    7. 3.7  CLK_01
    8. 3.8  I2C_01
    9. 3.9  GPIO_01
    10. 3.10 PMU_01
    11. 3.11 UART_01
  7. 4Revision History

3.10 PMU_01

Slow Transition Across Brown-Out Detect (BOD) Threshold Might Cause the Device to Hang

Revisions Affected

B

Details

If the VDDS supply voltage is held in the BOD threshold region (approximately 1.68V), the device might, on rare occasions, enter a lock-up state. In this state, the device draws approximately 2.25mA of current and will not recover even if the VDDS supply voltage is subsequently increased above the BOD threshold. Recovery from this state requires either a pin reset or reducing the VDDS supply voltage below the power-on reset (POR) threshold (1.0V), thereby triggering a POR reset.

The lock-up state is triggered if a brown-out-detect (BOD) event occurs during specific stages of boot code execution. There are two critical narrow time windows, each of approximately 10 ns duration, and both of these time windows occur within 100 μs to 1 ms after the reset event that initiates the boot code. The issue typically arises when the supply voltage ramps slowly across the BOD threshold. In such cases, supply resistance in combination with device startup current may cause the VDDS voltage to repeatedly dip below the BOD threshold as the device resets, increasing the likelihood of entering the lock-up state.

For Li-Ion and NiMH rechargeable batteries, a first-level protection disconnecting the chip VDDS supply would typically prevent the device from entering this state during battery discharge as the device power supply would fall below the POR threshold.

Even with non-rechargeable (primary) batteries, this issue may still occur, particularly as the battery approaches end-of-life and the voltage slowly decreases. In these cases, a workaround may not always be necessary, as the device will eventually require battery replacement, which would also trigger a power-on reset. However, the risk of lock-up cannot be ruled out.

CC2340R5-Q1 Diagram showing occurrenceFigure 3-1 Diagram showing occurrence

Workaround

The following workarounds must be implemented:

The specified operating supply voltage range for the device is 1.72V to 3.8 V. When using rechargeable batteries, the battery protection system must ensure one of the following:

  • The device supply voltage remains at or above the minimum operating supply voltage (1.72V) once powered on, or

  • If the device supply is discharged below the minimum operating supply voltage

    (1.72V), the device must be reset (pin or power-on reset) when the supply is charged above the minimum operating supply voltage (1.72V) again.