lpcware

LPC1313 system PLL fails to lock on IRC

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by mburton on Wed Mar 06 10:52:18 MST 2013

Hi,

I have a LPC1313 with no external crystal (VDD is 3V) and it is running OK at 12MHz using the IRC but when I try to use the PLL it never locks. I am using lpcopen 1.01 and this is the code used to setup the PLL:

  /* Set system PLL input to IRC */
  Chip_Clock_SetSystemPllSource(SYSCTL_PLLSRC_IRC);

  /* Powerup system PLL */
  Chip_SYSCTL_PowerUp(SYSCTL_POWERDOWN_SYSPLL_PD);

  /* Setup PLL for main oscillator rate (FCLKIN = 12MHz) * 6 = 72MHz
  MSEL = 5 (this is pre-decremented), PSEL = 1 (for P = 2)
  FCLKOUT = FCLKIN * (MSEL + 1) = 12MHz * 6 = 72MHz
  FCCO = FCLKOUT * 2 * P = 72MHz * 2 * 2 = 288MHz (within FCCO range) */
  Chip_Clock_SetupSystemPLL(5, 1);

Any

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