LPC812 power consumption

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by Stefbert on Wed Mar 25 12:41:04 MST 2015

I try to reproduce the messurement of the needed current of an LPC812 with the LPCXpresso LPC800 eval board. For that reason I cut all connections between the programming interface and the controller and connect only the signals SWDIOX, SWCLKX, GND and 3V3. An ampere meter is connect in the suppy wire.

Inside the datasheet of the device I found the following informations:
Conditions: Tamb = 25 °C; active mode entered executing code while(1){} from flash; all
peripherals disabled in the SYSAHBCLKCTRL register (SYSAHBCLKCTRL =0x1F); all peripheral
clocks disabled; internal pull-up resistors disabled; BOD disabled; low-current mode.
1 MHz - 6 MHz: IRC enabled; PLL disabled.
12 MHz: IRC enabled; PLL disabled.
24 MHz: IRC enabled; PLL enabled.
30 MHz: IRC disabled; SYSOSC enabled; PLL enabled.
Fig 14. Active mode: Typical supply current IDD versus supply voltage VDD

The figure shows the following currents:
24MHz approx. 2,1mA
12MHz approx. 1mA
6MHz approx.  700µA
2MHz approx.  500µA

My expectation is that I can reproduce this values. So I write a simple programm to verify this. The results I got are much higher than the given values.

So my question(s):
a) Did I missunderstand the datasheet an it is not possible to run the controller by 12MHz in active mode with a current near to 1mA ?
b) Can someone explain how to use the "low-current mode" ?

Thanks and best regards