topic Re: LPC1114 ADC sampling rate in LPCXpresso IDE

LPC1114 ADC sampling rate

lpcware — Wed, 15 Jun 2016 22:54:42 GMT

Content originally posted in LPCWare by Andrew on Thu Mar 15 20:36:50 MST 2012
Hi everyone,

I've got a simple question but I didn't manage to find the answer. The maximum ADC sampling rate is 4.5MHz according to the datasheet. What is the minimum sampling rate?

Thanks

Re: LPC1114 ADC sampling rate

lpcware — Wed, 15 Jun 2016 22:54:43 GMT

Content originally posted in LPCWare by Ex-Zero on Fri Mar 16 02:52:07 MST 2012

Quote:
The maximum ADC sampling rate is 4.5MHz according to the datasheet.

No :)

That's 'the clock for the ADC' as described in User Manual 10398:

Quote:

The APB clock (PCLK) is divided by CLKDIV +1 to produce the clock for the ADC, which should be less than or equal to 4.5 MHz. Typically, software should program the smallest
value in this field that yields a clock of 4.5 MHz or slightly less, but in certain cases (such as a high-impedance analog source) a slower clock may be desirable.

To calculate the maximum sampling rate you have to divide this clock with the number of clocks of your ADC setting:

11 clocks / 10 bits
10 clocks / 9 bits
9 clocks / 8 bits
8 clocks / 7 bits
7 clocks / 6 bits
6 clocks / 5 bits
5 clocks / 4 bits
4 clocks / 3 bits

So for a 10bit conversion with 4.5MHz ADC frequency you need >2.44µs = <409 kHz sampling rate :)

Quote:

What is the minimum sampling rate?

There's no minimum sampling rate. You can use whatever you want to trigger your ADC. A slow timer or Halley's Comet :rolleyes:

Re: LPC1114 ADC sampling rate

lpcware — Wed, 15 Jun 2016 22:54:44 GMT

Content originally posted in LPCWare by Andrew on Sun Mar 18 14:36:05 MST 2012
Thank you "Zero"

Re: LPC1114 ADC sampling rate

lpcware — Wed, 15 Jun 2016 22:54:44 GMT

Content originally posted in LPCWare by sourabh.jalnekar on Mon Aug 18 02:34:32 MST 2014
can anyone tell me how to set the sampling frequency to 100 khz or 200 khz in lpc1574