LM3S1968 Datasheet, PDF (657/709 Pages) List of Unclassifed Manufacturers – Microcontroller

Stellaris^® LM3S1968 Microcontroller
21.2.2
Clocks
Table 21-8. Phase Locked Loop (PLL) Characteristics
Parameter Parameter Name
Min
Nom
Max
Unit
f_{ref_crystal}
f_{ref_ext}
f_pll
Crystal reference^a
External clock reference^a
PLL frequency^b
3.579545
-
3.579545
-
-
400
8.192
8.192
-
MHz
MHz
MHz
T_READY
PLL lock time
-
-
0.5
ms
a. The exact value is determined by the crystal value programmed into the XTAL field of the Run-Mode Clock Configuration
(RCC) register.
b. PLL frequency is automatically calculated by the hardware based on the XTAL field of the RCC register.
Table 21-9 on page 657 shows the actual frequency of the PLL based on the crystal frequency used
(defined by the XTAL field in the RCC register).
Table 21-9. Actual PLL Frequency
XTAL
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
Crystal Frequency (MHz)
3.5795
3.6864
4.0
4.096
4.9152
5.0
5.12
6.0
6.144
7.3728
8.0
8.192
PLL Frequency (MHz)
400.904
398.1312
400
401.408
398.1312
400
399.36
400
399.36
398.1312
400
398.6773333
Error
0.0023%
0.0047%
-
0.0035%
0.0047%
-
0.0016%
-
0.0016%
0.0047%
0.0047%
0.0033%
Table 21-10. Clock Characteristics
Parameter Parameter Name
Min
Nom
Max
f_IOSC
f_IOSC30KHZ
f_XOSC
f_{XOSC_XTAL}
f_{XOSC_EXT}
Internal 12 MHz oscillator frequency
8.4
12
15.6
Internal 30 KHz oscillator frequency
15
30
45
Hibernation module oscillator frequency
-
4.194304
-
Crystal reference for hibernation oscillator
-
4.194304
-
External clock reference for hibernation
module
-
32.768
-
f_MOSC
Main oscillator frequency
1
-
t_{MOSC_per}
Main oscillator period
125
-
f_{ref_crystal_bypass}
Crystal reference using the main oscillator
(PLL in BYPASS mode)^a
1
-
8.192
1000
8.192
f_{ref_ext_bypass}
External clock reference (PLL in BYPASS
mode)^a
0
-
50
f_{system_clock}
System clock
0
-
50
a. The ADC must be clocked from the PLL or directly from a 16-MHz clock source to operate properly.
Unit
MHz
KHz
MHz
MHz
KHz
MHz
ns
MHz
MHz
MHz
July 15, 2014
657
Texas Instruments-Production Data