LM3S308 Datasheet, PDF (498/537 Pages) Texas Instruments – ARM and Thumb are registered trademarks and Cortex is a trademark

Electrical Characteristics
Figure 18-1. Load Conditions
pin
C_L = 50 pF
GND
18.2.2 Clocks
Table 18-7. 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
-
-
200
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 18-8. Clock Characteristics
Parameter
Parameter Name
Min
Nom
Max
f_IOSC
f_MOSC
t_{MOSC_per}
f_{ref_crystal_bypass}
Internal oscillator frequency
7
12
Main oscillator frequency
1
-
Main oscillator period
125
-
Crystal reference using the main oscillator
1
-
(PLL in BYPASS mode)^a
22
8
1000
8
f_{ref_ext_bypass}
External clock reference (PLL in BYPASS
0
-
25
mode)^a
f_{system_clock}
System clock
0
-
25
a. The ADC must be clocked from the PLL or directly from a 16.667-MHz clock source to operate properly.
18.2.2.1 System Clock Specifications with ADC Operation
Unit
MHz
MHz
ns
MHz
MHz
MHz
Table 18-9. System Clock Characteristics with ADC Operation
Parameter Parameter Name
Min
f_sysadc
System clock frequency when the ADC module is
16
operating (when PLL is bypassed)
Nom
Max
-
-
Unit
MHz
18.2.3 JTAG and Boundary Scan
Table 18-10. JTAG Characteristics
Parameter
No.
J1
J2
Parameter Parameter Name
f_TCK
TCK operational clock frequency
t_TCK
TCK operational clock period
Min
Nom
Max
0
-
10
100
-
-
Unit
MHz
ns
498
June 18, 2012
Texas Instruments-Production Data