8.1 Low Power Design on PIC32CXBZ3 Devices

PIC32CXBZ3 examples and stacks supports Sleep and Deep Sleep low power modes as part of Harmony framework for WBZ351. Sleep and Deep Sleep Modes are synonymous to Standby and Backup Modes. Throughout this document, the Sleep Mode is referred as Standby and Deep Sleep mode as Backup mode.

Difference between Sleep and Deep Sleep Low Power Mode:

  1. Sleep Low Power Mode:

    1. Application layer calls BLE stack to enable advertising, BLE stack will continue sending and receiving advertising Tx and Rx periodically until the application layer disables it

    2. System continues to operate between Active Mode and Sleep Mode periodically based on the ADV Tx and Rx

    3. Application layer can have peripherals running in sleep/standby low power mode

  2. Deep Sleep Low Power Mode:

    1. Application layer calls BLE stack to enable Deep Sleep Advertisement, BLE stack will backup advertisement parameters and data into backup SRAM and perform one time advertising event

    2. After entering Deep Sleep low power mode, the system wakes up from reset, whereby all parameters are lost. Backup SRAM (retained in deep sleep low power mode)is used to save the advertisement parameters when waking up from reset.

    3. Application layer will put system into Deep Sleep low power mode and control the wakeup time based on RTC timer (which runs in Deep Sleep low power mode)

    4. Once the system wakes up from Deep Sleep low power mode, application layer triggers advertisement again by recovering the adverstisement and data partamters that are stored in backup SRAM

Low Power Design of a system involves optimizing power both in Hardware and Software. To name a few:

  • System Design

    • MLDO vs Buck Mode (DC\DC), Operating in Buck Mode yields to power consumption savings of about

    • Board design to be able to measure the current consumed by the PIC32CXBZ3 device alone as there can be multiple components in the system

    • Device Errata needs to be verified and special attention to issues that affect Device Power Consumption

    • Lower System Clock speed from 64 MHz to 48 MHz, some applications can operate with a lower system clock speed of 48 MHz

  • Hardware Design
    • Configuring the Transmitter power - @ 0dBm with Buck Mode on @ 64 MHz, the PIC32XCBZ3 device draws 22.72 mA
      • @+12 dBm Transmitter (Buck Mode @64 MHz) current consumption is 42.82 mA
      • @+4 dBm Transmitter (Buck Mode @64 MHz) current consumption is 24.98 mA
      • At Power up, all GPIO's are inputs. Unused GPIOs should be configured as input and pull down configuration
  • Software Design