I'm road testing the Ultra-Low Power Arm Cortex-M4 Darwin MCU EVM. In this blog post I measure the power going to the MAX32660.
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Power Modes
The MAX32660 has a set of power saving options. The obvious one is to lower the clock cycle. The lower the frequency, the less power the chip requires.
Another one is the supply voltage. The controller can be sourced from as low as 1.62 V up to 3.63 V. I've used 1.8 V and 3.3 V in this exercise.
And there are the configurable power modes and module-specific power save options.
source: Webinar Recording: What Can You Do With the World’s Smallest Arm
Cortex M4 with FPU Microcontroller?
The MAX32660 has 4 power modes, all described in the user guide.
- Active (tested in this blog in 3 different configurations: with unused RAM on, in light sleep and switched off)
- Sleep
- Deep Sleep
- Backup
source: Webinar Recording: What Can You Do With the World’s Smallest Arm Cortex M4 with FPU Microcontroller?
The user guide details the functionality, but if you have the time, check out the webinar. It reviews the modes and also touches low supply voltage vs frequency.
LP Example
The software pack has a good low power example. It allows you to cycle through the modes, either via a button click or timer based.
It's worth checking out both ways of cycling, because they show different options to wake up the controller from the sleep modes.
The example, available when you install the software, has the following configurable settings:
- button or timer controlled
- time between modes for the timer based option
- use console to display the modes (enables UART module, so account for that when measuring)
- enable the deepest Backup mode (for some reason, the button based example does not recover from that mode, the timer based one does)
This is the cycle:
- Running in ACTIVE mode
- All unused RAMs placed in LIGHT SLEEP mode
- All unused RAMs shutdown
- Entering SLEEP mode
- Entering DEEPSLEEP mode
- Entering BACKUP mode
I've measured the current consumption for 1.8 and 3.3 V for each mode.
The current is for all components on the controller side of the EVM. That includes the pull-ups, quiescent current in the LED circuit and the EEPROM.
source: MAXIM EVK data sheet
Here are 3 measurements in mA, all with console off:
The capture below shows a 3.3 V cycle without UART, in clocked mode, 10 s per state.
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