[time-nuts] Microchip PIC CTMU

[David]

Was that a couple of nanoseconds of resolution or minimum time
interval?

Based on the simplified schematic which shows the current source being
controlled by a single XOR gate, it looks to me like the minimum time
interval is much longer than the achievable single shot resolution.

On Tue, 10 May 2016 21:37:08 -0400, you wrote:

>Hi
>
>I have not dug into them for several years. Back when I did, you were pushing 
>their limits as a couple of nanoseconds without getting into things like lots of 
>averaging. 
>
>Bob
>
>> On May 10, 2016, at 8:29 PM, David <davidwhess at gmail.com> wrote:
>> 
>> I ran a search through the time-nuts archives and found only one
>> mention of this a couple years ago asking the same question which is,
>> has anybody explored the capabilities of the Microchip PIC CTMU for
>> use as a time to digital converter or programmable delay?
>> 
>> The Microchip datasheets lack detailed performance specifications but
>> my conservative estimate is that resolution down to 500ps over 200ns
>> using the built in 10 bit ADC should be possible without complex
>> calibration.  (The PIC series ADCs with more than 10 bits are pretty
>> horrible.)
>> 
>> See What You Can Do with the CTMU:
>> http://ww1.microchip.com/downloads/en/AppNotes/CTMU%2001375a.pdf
>> 
>> Overview of Charge Time Measurement Unit (CTMU):
>> http://www.microchip.com/stellent/groups/SiteComm_sg/documents/DeviceDoc/en542792.pdf
>> 
>> PIC18(L)F2X/4XK22 w/10 Bit ADC:
>> http://ww1.microchip.com/downloads/en/DeviceDoc/39977f.pdf
>> 
>> PIC18F66K80 w/12 Bit ADC:
>> http://ww1.microchip.com/downloads/en/DeviceDoc/39977f.pdf
>> 
>> I prefer more discrete implementations but this might be useful for
>> its higher integration, lower cost, and simplicity in less demanding
>> applications.