power consumption of RTC using OSCULP32K vs XOSC32K

Go To Last Post
7 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

It was mentioned in AN2515 and  AN2633 that external 32k crystal typically consume more power than internal ULP OSC. But when I look at the power consumption published in DS, for example for ATtiny1614, Table 37-5. a RTC running at 1.024k  from XOSC32K consume 0.69uA, from OSCULP32K it consume 0.71uA. It seems XOSC32K should be as efficient as OSCULP32K.

Any experience on power consumption of these clocks ? I want to use XOSC32K but want to avoid having to do power optimization if unnecessary. 

Thank you.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

No experience but a general philosophical comment.

 

Any time you need to care about 0.002uA, you need to do "power optimization".

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Jim, I think you have one too many zeros in there but I think your argument still stands.

Letting the smoke out since 1978

 

 

 

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Correct. The difference is 0.02uA. That is 20nA.

 

Jim

 

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

XYXD wrote:

 But when I look at the power consumption published in DS, for example for ATtiny1614, Table 37-5. a RTC running at 1.024k  from XOSC32K consume 0.69uA, from OSCULP32K it consume 0.71uA. It seems XOSC32K should be as efficient as OSCULP32K.

 

Your are best to build and measure, when sub uA currents matter.

You will likely find the Xtal itself has some influence on current.

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Thank you. I will just have to measure...

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Also, both numbers are likely "TYPICAL". That means that there is some expected variation above and below those numbers. Any one device (and crystal) could see significant differences from those. Measuring a single unit could lead you to an incorrect (e.g. invalid) conclusion. If its that important to you, be prepared to measure hundreds to thousands.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net