Low Power SAADC

RE: Low Power SAADC

haakonsh — Thu, 08 Feb 2018 15:52:42 GMT

A decent Power analyser should not have a 50Hz hum of that magnitude, I believe three might be a measurement error.

I need you to describe your measurement set-up, and please be specific. ie what is the brand and model of the instruments used, and how are they connected to the DK. Have you followed the steps in Measuring current? etc.

You should disable your SPI code until you have been able to verify that the current measurements with the SAADC code are as expected, or else it will be difficult to analyse the measurements.

RE: Low Power SAADC

bryanhsieh — Thu, 08 Feb 2018 14:32:37 GMT

Hi Hakon,

Thanks for the prompt response.

Why does the additional 1mA only appear when more than one channel is initialised?

Here is the current consumption from a DC power analyser ( units amps and seconds, sampling freq = 200Hz ), SPI is also on to send data to external NAND memory, I have worked out the main cause of the high idle current is due to the SAADC.

The power consumption is affected by the mains noise as shown in the graph but there is a DC current of around 2mA when this should be around 0.3mA?

Thanks,

Bryan

RE: Low Power SAADC

haakonsh — Thu, 08 Feb 2018 12:28:14 GMT

Hey Bryan,

The 300mA static current consumption might be a pull-up connected directly to ground. The pull-ups are typically 13Kohm. At 3V the current consumption of a 13K resistor bettween VDD and GND is 3V/13Kohm = ~230µA.

It can also be a HFCLK constantly running, ie PPI is set to 'constant latency'.

The additional 1mA is probably the SAADC + EasyDMA.

Do you have a scope of the current consumption?

Cheers,

Håkon.