current draw of LPC55S16 in deep power down mode

[dank60]

i loaded the power_manager_lpc project from sdk for LPC55S16-EVK evaluation board. 

I set the micro in deep power down mode (menu option 4)

I measured the current across the three jumpers on the board and got these results:

jumper J20 = 162uA

jumper J21 = 10nA

jumper J22 = 710nA 

datasheet LPC55S1x_PDS on page 77 shows 635 nA as typical power consumtion for this mode if RTC oscillator is running with external srystal and 4kB SRAM powered.

I also tried without ram powered but consumption has changet very little.

Do I have to change the code of the example to reach the consumtions declared in the datasheets or are the latter incorrect?

[ZhangJennie · Accepted solution]

Hi dank60 

The low power demo code in SDK package is for different low power mode entrance and wakeup demonstration. We can't use it directly to get power consumption data shown in datasheet .

The power consumption data shown in datasheet are measured when the MCU GPIO output is low and pull-up is prohibited, and all oscillators and analog domains are turned off. As the demo code is for demonstration purpose, UART, and some wakeup source powers turn on. if you test it with connecting debug probe, debug port also costs power consumption. You need to make sure all the unnecessary powers are off, set the unused GPIO as the pull-up input according to the actual situation (it can also be set as the output low when the pin is floating) to reduce the power consumption.

Besides, the datasheet statistics based on experimental MCU bare board which makes sure a simple testing enviroment. the demo board peripheral resources are far more complex than experimental board.

If user has high requirements for low power consumption, users need to carefully optimize the code to get the best low power design.

Thanks,

Jun Zhang

[dank60]

Ok Jennie, thanks a lot