topic KL0 power consumption @ 4 mhz - 3x higher than expected. in Kinetis Microcontrollers

KL0 power consumption @ 4 mhz - 3x higher than expected.

austinappleby — Sat, 24 Aug 2013 09:38:12 GMT

I'm doing some basic power consumption tests on a MLK05Z32 chip and am seeing much higher power consumption than expected - with a 4 mhz system clock (fast internal reference clock, FLL disabled) and 2 mhz bus clock (OUTDIV4=1), the chip is drawing about 1.5 milliamps in a simple LED blink test. That's about 3x the draw of the competitor's chip with the same clocks & code - rather disappointing.

I'm looking for ways to reduce the power draw, but not having much luck - the application I'm evaluating the chip for will require some cycle-accurate bitbanging, so I don't think VLPR mode will work for me as the 0.8 mhz flash clock in that mode slows things down whenever there's an instruction cache miss.

Are there any other ways to reduce the power draw that I'm missing? I need deterministic 4 mhz operation, no wait states.

-Austin

Re: KL0 power consumption @ 4 mhz - 3x higher than expected.

Paul_Tian — Tue, 27 Aug 2013 01:19:33 GMT

Hi, Austin

The current consume depends on both code and hardware. Would you please help to provide your schematic then tell me where you measure current. Thanks.

Best Regards

Paul

Re: KL0 power consumption @ 4 mhz - 3x higher than expected.

austinappleby — Wed, 28 Aug 2013 05:46:43 GMT

There's no schematic to it - it's a bare MKL05Z32 chip on a breakout board with a 1 uF ceramic capacitor right next to it and I'm measuring the current into VDD through a 1 ohm resistor.

The only thing the code is doing is switching to the internal fast reference clock (IRCS 1, FCRDIV = 0, CLKS = 1, LP = 1, OUTDIV4 = 1), enabling PTB0 (SIM_SCGC5.PORTB = 1, PORTB_PCR0.MUX = 1, GPIOB_PDDR = 1), and then toggling the pin once a second.