TIDUF89 September   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Detection Theory
    2. 1.2 Multi-Pass Architecture
  8. 2System Overview
    1. 2.1 System Design Theory
      1. 2.1.1 Long Detection Range
        1. 2.1.1.1 Antenna Design for Long Detection Range
        2. 2.1.1.2 SNR Compensation for Long Detection Range
        3. 2.1.1.3 Smart Detection Logic
      2. 2.1.2 Low Power Consumption
        1. 2.1.2.1 Efficient Chirp Design
        2. 2.1.2.2 Deep Sleep Power Modes
        3. 2.1.2.3 Hardware Accelerator
      3. 2.1.3 Low False Alarm Rate
        1. 2.1.3.1 Typical Causes of False Alarms
        2. 2.1.3.2 False Alarms Outside the Detection Zone
        3. 2.1.3.3 False Alarms Within the Detection Zone
        4. 2.1.3.4 Adaptive State Machine
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Software Requirements
    3. 3.3 Test Setup
      1. 3.3.1 Test 1 - Detection Range
      2. 3.3.2 Test 2 - False Alarm Rate
      3. 3.3.3 Test 3 - Power Consumption
    4. 3.4 Test Results
  10. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
  11. 5Tools and Software
  12. 6Document Support
  13. 7Support Resources
  14. 8Trademarks
  15. 9About the Authors

2.1.2.2 Deep Sleep Power Modes

The IWRL6432AOP consumes very little power through the deep sleep modes, which achieve <0.5mW power consumption when the radar is not being used. While xWRL6432 Low Power Radar - Power Optimization Techniques, application note covers this in extensive detail, this section can focus specifically on the ways to reduce power that do not affect detection range or false alarm rate.

The IWRL6432AOP device can save power in deep sleep by reducing the amount of memory retained in the Deep Sleep mode. On the IWRL6432, memory instances consume approximately 45µW or 64kB in power-down retention mode. If memory within a cluster is not retained, IWRL6432 can consume approximately 20µW/64kB. To further save power when memory is not retained, some memory clusters on the IWRL6432 are grouped together, and power switches are deployed on the corresponding SRAM power rails. If all the clusters in a group are not retained during Deep Sleep, switches for the group are opened, completely powering off the group, causing the memory to consume 0µW/kB while completely powered off (no retention).

These switches can be set in sysconfig. Table 2-2 explains which clusters correspond to which sections in memory.

Table 2-2 Memory Addresses for Each Cluster
Cluster No. Memory Segment Cluster Name Size (kB) Starting Memory Location Notes
APPSS Cluster #1 RAM_1 RAM1A 64 0x00400000
APPSS Cluster #3 RAM_1 RAM1B 64 0x00410000
APPSS Cluster #4 RAM_1 RAM1C 128 0x00420000
APPSS Cluster #2 RAM_2 RAM2A 16 0x00440000
APPSS Cluster #5 RAM_2 RAM2B 112 0x00444000
APPSS Cluster #5 RAM_3 RAM3 128 0x00460000
APPSS Cluster #6 APP_SHMEM_1 Shared RAM 1 128 0x00480000 When accessed from HWA, starts at 0x60000000
APPSS Cluster #6 APP_SHMEM_2 Shared RAM 2 128 0x004A0000 When accessed from HWA, starts at 0x60000000

The linker.cmd file can be used to dictate where data is stored in memory. Efficient design can store the variables that get reset every frame, such as the major motion point cloud, in clusters that are NOT retained during deep sleep. However, other variables that are not reset every frame, such as the occupancy status in each detection zone, needs to be placed in memory banks that are retained during deep sleep. This is accomplished in the video doorbell demo by default.