Datasheet

OSCIN
OSCOUT
C1
(see Note A)
C2
Crystal
(a)
OSCIN OSCOUT
(b)
External
(toggling 0 V to 3.3 V)
Clock Signal
Note A: The values of C1 and C2 should be provided by the resonator/crystal vendor.
Kelvin_GND
Note B: Kelvin_GND should not be connected to any other GND.
(see Note B)
75
RM57L843
www.ti.com SPNS215C –FEBRUARY 2014–REVISED JUNE 2016
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System Information and Electrical SpecificationsCopyright © 2014–2016, Texas Instruments Incorporated
6.6 Clocks
6.6.1 Clock Sources
Table 6-11 lists the available clock sources on the device. Each clock source can be enabled or disabled
using the CSDISx registers in the system module. The clock source number in the table corresponds to
the control bit in the CSDISx register for that clock source.
Table 6-11 also lists the default state of each clock source.
Table 6-11. Available Clock Sources
CLOCK
SOURCE NO.
NAME DESCRIPTION DEFAULT STATE
0 OSCIN Main Oscillator Enabled
1 PLL1 Output From PLL1 Disabled
2 Reserved Reserved Disabled
3 EXTCLKIN1 External Clock Input 1 Disabled
4 CLK80K Low-Frequency Output of Internal Reference Oscillator Enabled
5 CLK10M High-Frequency Output of Internal Reference Oscillator Enabled
6 PLL2 Output From PLL2 Disabled
7 EXTCLKIN2 External Clock Input 2 Disabled
6.6.1.1 Main Oscillator
The oscillator is enabled by connecting the appropriate fundamental resonator/crystal and load capacitors
across the external OSCIN and OSCOUT pins as shown in Figure 6-3. The oscillator is a single-stage
inverter held in bias by an integrated bias resistor. This resistor is disabled during leakage test
measurement and low power modes.
NOTE
TI strongly encourages each customer to submit samples of the device to the
resonator/crystal vendors for validation. The vendors are equipped to determine which load
capacitors will best tune their resonator/crystal to the microcontroller device for optimum
start-up and operation over temperature and voltage extremes.
An external oscillator source can be used by connecting a 3.3-V clock signal to the OSCIN terminal and
leaving the OSCOUT terminal unconnected (open) as shown in Figure 6-3.
Figure 6-3. Recommended Crystal/Clock Connection