topic Re: 16MHZ Crystal to LPC1549JBD48 in LPC Microcontrollers

16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:20 GMT

Content originally posted in LPCWare by jhd on Fri Feb 05 07:08:02 MST 2016
Hi!,

Is it possible to use a 16 Mhz Crystal instead of a 12Mhz? Does this increase the baud rate?

ABLS2-16.000MHZ-D4Y-T instead of a ABLS2-12.000MHZ-D4Y-T

Regards

Re: 16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:20 GMT

Content originally posted in LPCWare by R2D2 on Fri Feb 05 07:22:49 MST 2016

Quote: Javier.Hernandez
Is it possible to use a 16 Mhz Crystal instead of a 12Mhz? Does this increase the baud rate?

Datasheet:

Quote:
The system oscillator operates at frequencies of 1 MHz to 25 MHz.

Re: 16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:21 GMT

Content originally posted in LPCWare by jhd on Fri Feb 05 12:11:53 MST 2016
Thank you R2D2,

Cx1 = Cx2 = 2 x CL - CP is appicable to both RTC oscillator and Crystal?

If 16Mhz Crystal has 18pF of load capacitance and 40 Ohms and ESR, XTAL_IN and XTAL_OUT pads has 3pF, then:

Cx1 = Cx2 = 2 x 18 -3

Cx1 = Cx2 = 33pF (to ABLS2-16.000MHZ-D4Y-T)

Is right?

33pF if the formula is applicable so: Cx2 = (2 * 18) -3 , because if is so: Cx2 = 2 * (18 - 3) the result is 30pF

Re: 16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:22 GMT

Content originally posted in LPCWare by R2D2 on Fri Feb 05 14:53:39 MST 2016

Quote: Javier.Hernandez
Thank you R2D2,

Cx1 = Cx2 = 2 x CL - CP is appicable to both RTC oscillator and Crystal?

No. The usual way to calculate the caps is explained here:

https://blog.adafruit.com/2012/01/24/choosing-the-right-crystal-and-caps-for-your-design/

CL = (C1 * C2) / (C1 + C2) + Cstray

Or you just look in table 32 of DS and select 18pF :D

BTW: There are nice small crystals available, something like:

http://www.mouser.de/ProductDetail/CTS/403C11A16M00000/?qs=%2fha2pyFadugbYxX5bkUvgi75eNTfe%252bSl4%252bedPQObWYvRJqeM9MpGMjNsmFO9kL%252bk

Re: 16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:22 GMT

Content originally posted in LPCWare by jhd on Sat Feb 06 05:01:42 MST 2016
Thanks R2D2,

CTS crystal is nice (+/-10ppm) but I have choosed ABM11 because I need 3D file. http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=189376144&uq=635903287418439415

ABM11-16.000MHZ-B7G-T >>> 16MHz ±15ppm Crystal 10pF 150 Ohm

Then,

C1, C2 = 2*CL – 2*Cstray

CL = 10pF
C1, C2 = ?
Cstray = 3pF

C1, C2 = (10pF * 10pF) - 6 , result = 14pF

Other formule:

CL = (C1 * C2) / (C1 + C2) + Cstray

CL = 10pF
C1, C2 = 14pF
Cstray = 3pF

C1, C2 = (14pF * 14pF) / (14pF + 14pF) + 3pF = 10pF

Then, I need 2 x 14pF capacitors to ABM11-16.

Regards

Re: 16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:23 GMT

Content originally posted in LPCWare by R2D2 on Sat Feb 06 08:25:24 MST 2016

Quote: Javier.Hernandez
C1, C2 = (10pF * 10pF) - 6 , result = 14pF

Re: 16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:24 GMT

Content originally posted in LPCWare by jhd on Sat Feb 06 10:04:56 MST 2016
jajaj sorry is

C1, C2 = (2 * 10pF) - 6 , result = 14pF

Re: 16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:24 GMT

Content originally posted in LPCWare by IanB on Sat Feb 13 02:41:33 MST 2016
Don't worry about crystal load caps - every crystal I've ever used works with 15pF caps.

Some even work with only one cap (on the XTAL-IN pin)

Re: 16MHZ Crystal to LPC1549JBD48

lpcware — Wed, 15 Jun 2016 17:11:25 GMT

Content originally posted in LPCWare by jhd on Thu Feb 25 11:36:26 MST 2016
Thank you!

Regards