Thanks, Mike, good stuff.

--Bob

michael brown wrote:

>From: "Bob Axtell"
>
>
>  
>
>>I am interested because I have an LF88 in a current sensitive app, but
>>I THOUGHT it worked OK (currents lower than that).
>>
>>er.. maybe a leaking cap? a Tantalum or ceramic disk? A WRONG value
>>R someplace? Swap any standard electrolytics for Tantalum.
>>
>>Are those the LF88 specs or the F88 specs? If I recall, the LF88 was
>>    
>>
>MUCH
>  
>
>>better. Can you try an LF88? I have an extra SOIC18 version..
>>    
>>
>
>Even though my problem turned out to be an apparent bug in the hardware,
>I wanted to comment on this last part.  AIUI, all parts have the same
>specs except that the L (low voltage) parts are guaranteed to work at a
>lower voltage.  Voltage certainly plays an important role in how much
>current is drawn, so the L parts are "better" in that respect, but they
>aren't otherwise different from the 'non-L' parts.  IOW, at 5V they are
>all the same.  ;-)  The DS1307 requires at least 4.5V, but I'm sure
>there are some 2V or 3V minimum parts available.
>
>I've been experimenting, now before I put it to sleep, I power off the
>EEPROMs, DS1307, LM34 and my external Vref for the ADC.  Sleep current
>for the whole circuit is <5uA.  The DS1307 runs off a lithium backup
>cell when the circuit is asleep.  The square wave output of the DS1307
>continues to function with no power applied to the Vcc pin (Vbat does
>the job).  I use a way big (3.3M) pull-up on the square wave output for
>super-low current draw (1.5uA) during the low half of the cycle.  The
>RB0 int fires on the falling edge with no problems caused by the really
>weak pull-up.  The duty cycle is only 1Hz so rise time is not an issue.
>The 1.5uA is small but it still accounts for a large chunk of the total
>sleep current of the circuit.
>
>  
>


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