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06/09/13 19:58
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#189891 - Low-power MCU needed
For a current project, I chose the Atmel AT89LP214 based on datasheet data. Low power consumption was one of the requirements.

The MCU spends most of the time in idle mode with a timer running. Then when the timer overflows, a port pin is flipped, the timer registers are reloaded, and idle mode is entered again. Based on the datasheet, I chose a 2MHz ceramic resonator. The current should be about 2.7mA in active mode and about 0.6mA in idle mode. The actual current is 2.7mA all the time - not what I expected. Using the internal 8MHz oscillator, the current should be 6/2mA, and it's actually the same 2.7mA, with the software running at 4x speed. If I change the software to work correctly at 8MHz, the consumption drops to 2.55mA. Better, but not great.

Are there better alternatives?

The requirements are quite simple:

- 5V operation
- 4 available push/pull output pins
- 1kB flash
- small(ish) size

I chose the LP214 because of the DIL-14 house also. A DIL-device is easy to program in a ZIF socket, and there isn't space for a DIL-14 and a programming header on the board. The IC shouldn't be too small either, as the boards have to be hand-assembled. A narrow SOIC-14 -20 would be ideal. The IC + programming header would be the same size as the DIL-14.

A device with an internal precision clock would be nice - provided it can be divided to be slow enough. A 12-clock device running at 4MHz is fast enough, so much "power" isn't needed...

Mikkel

List of 44 messages in thread
TopicAuthorDate
Low-power MCU needed            01/01/70 00:00      
   OK, but wrong            01/01/70 00:00      
      Wrong how?            01/01/70 00:00      
         Silabs options            01/01/70 00:00      
            C8051F99x            01/01/70 00:00      
               Silabs            01/01/70 00:00      
                  look it up            01/01/70 00:00      
                     Looked up            01/01/70 00:00      
                        f53, no            01/01/70 00:00      
                        C8051F537A is OK            01/01/70 00:00      
         the current in active mode is not the issue            01/01/70 00:00      
            Inactive current            01/01/70 00:00      
         re: wrong            01/01/70 00:00      
            Consumers            01/01/70 00:00      
   Zilog Z51F0410             01/01/70 00:00      
      Zilog            01/01/70 00:00      
   Check you are entering idle ?            01/01/70 00:00      
   idle current            01/01/70 00:00      
      Idle test            01/01/70 00:00      
         re:            01/01/70 00:00      
            It floats! It floats!            01/01/70 00:00      
               re:floats            01/01/70 00:00      
               re:floats            01/01/70 00:00      
                  Timers            01/01/70 00:00      
         More idle tests            01/01/70 00:00      
            Better regulator?            01/01/70 00:00      
               LR8K4 450V regulator             01/01/70 00:00      
         also try CLKREG            01/01/70 00:00      
            Clk Dividers are a good idea            01/01/70 00:00      
               No dividers            01/01/70 00:00      
                  LP52 is cheaper too...            01/01/70 00:00      
                     LP52            01/01/70 00:00      
                        No GND pin?            01/01/70 00:00      
         re:idle            01/01/70 00:00      
         Totally idle            01/01/70 00:00      
            Checks            01/01/70 00:00      
               More checks            01/01/70 00:00      
                  Power Down ?            01/01/70 00:00      
                  test setup            01/01/70 00:00      
   STC            01/01/70 00:00      
      C8051F86x/85x ?            01/01/70 00:00      
      Maybe not such a good choice, after all?            01/01/70 00:00      
         Support?            01/01/70 00:00      
            '51 support            01/01/70 00:00      

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