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LPC43xx sleep mode consumption

Question asked by lpcware Employee on Jun 15, 2016
Latest reply on Mar 9, 2017 by Stephen Carey
Content originally posted in LPCWare by ptamo on Fri Nov 07 07:21:32 MST 2014
Hello,

I use the LPC4330 in a custom board. It is clocked at 204Mhz and executing code from internal RAM.
I am trying to reduce power consumption using the sleep mode whenever is possible. I have found that sleep mode reduces the total current consumption only 26mA. I believe that the power consumption reduction must at least 76mA as the datasheet specifies 81mA@204Mhz for the core in active mode and 5mA at sleep.
I use deep sleep mode in some situations were the microcontroller is not used and this mode reduces power consumption 180mA. If I reduce main clock to 102Mhz the consumption is halved, this seems coherent.
I am sure that the microcontroller is entering sleep after the WFI instruction, I use a GPIO to monitor when it enters and leaves it.
All current measurements are done without debugger attached and board power cycled after detaching debugger.

I can't mesure the total current consumption of the LPC alone as there are other peripherals at the board, but its current consumption must be more than 180mA. I find it too much considering that code is being executed from internal RAM. I mesure it inside a while(1){} with interrupts disabled. The only peripherals that are clocked are SSP0, SSP1, UART0 and the external memory controller, the rest of peripheral clocks are disabled.

We use the LPC4357 in another custom board also clocked at 204Mhz. The sleep mode has the same effect. Current consumption is barely reduced.

My main doubts are:
-Is it normal that sleep mode only saves 26mA at 204Mhz?
-Is it normal that the LPC4330 executing a while(1){} from RAM drains more than 180mA?

This unanswered 2013 post seem to describe the same problem:
http://www.lpcware.com/content/forum/lpc43xx-sleep-mode

Thanks in advance
Rubén

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