MSP430FR2633: Standby power consumption with proximity

Hello Darren,

The standby power consumption depends on couple of the factors:

• Low frequency clock source:
  • Crystal: Low current, best accuracy. LPM3 base current ~ 1.2uA
  • REFO: High current, good accuracy. LPM3 base current ~ 16uA
  • VLO: Low current, porr accuracy. LPM3 base current: ~1uA
• Application Scan period:
  • This is the amount of time between each sampling of the user interface. The scan period has a direct effect on the power consumption, as it controls the duty cycle of the application. When a lower period (higher rate) is selected, the CapTIvate analog and possibly the CPU are waking up much more frequently- consuming more power. The design tradeoff here is response time versus power consumption. Scanning less often reduces the power consumption, but also increases the response time of the user interface.
• Sensor Measurement time:
  • This depends on Frequency Divider (Conversion clock frequency selection) and Conversion Count (Base number of charge transfers without a touch).
  • Conversion clock frequency and required Conversion count depends on the actual sensor design.

CapTIvate has the Wake on proximity mode which turn off the CPU and using the FSM to handle the measurement as well as basic processing of the proximity sensor. If there is no touch or proximity event the device can keep staying at the low power mode without CPU interaction. The proximity sensor will wake up the CPU and measure all other sensors on the board. 

For our BOOSTXL-CAPKEYPAD EVM, there is a proximity sensor and the power consumption in WOP mode (standby mode) is ~ 8uA. 

Thanks,

Yiding