MSP430FR2111 Datasheet, PDF (18/75 Pages) Texas Instruments – Mixed-Signal Microcontrollers

MSP430FR2111, MSP430FR2110
SLASE78A – AUGUST 2016 – REVISED AUGUST 2016
www.ti.com
5.13.3 Clock Specifications
Table 5-3 lists the characteristics of the XT1 in low-frequency mode.
Table 5-3. XT1 Crystal Oscillator (Low Frequency)
over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted)⁽¹⁾
f_{XT1, LF}
PARAMETER
XT1 oscillator crystal, low
frequency
TEST CONDITIONS
LFXTBYPASS = 0
V_CC
MIN TYP MAX UNIT
32768
Hz
DC_{XT1, LF}
f_XT1,SW
XT1 oscillator LF duty cycle
XT1 oscillator logic-level square-
wave input frequency
Measured at MCLK,
f_LFXT = 32768 Hz
LFXTBYPASS = 1 ^{(2) (3)}
30%
70%
32768
Hz
DC_{XT1, SW}
LFXT oscillator logic-level square-
wave input duty cycle
LFXTBYPASS = 1
40%
60%
OA_LFXT
C_L,eff
Oscillation allowance for
LF crystals ⁽⁴⁾
Integrated effective load
capacitance ⁽⁵⁾
LFXTBYPASS = 0, LFXTDRIVE = {3},
f_LFXT = 32768 Hz, C_L,eff = 12.5 pF
See ⁽⁶⁾
200
kΩ
1
pF
t_START,LFXT Start-up time ⁽⁷⁾
f_Fault,LFXT Oscillator fault frequency ⁽⁸⁾
f_OSC = 32768 Hz
LFXTBYPASS = 0, LFXTDRIVE = {3},
T_A = 25°C, C_L,eff = 12.5 pF
XTS = 0⁽⁹⁾
1000
ms
0
3500 Hz
(1) To improve EMI on the LFXT oscillator, observe the following guidelines:
• Keep the trace between the device and the crystal as short as possible.
• Design a good ground plane around the oscillator pins.
• Prevent crosstalk from other clock or data lines into oscillator pins XIN and XOUT.
• Avoid running PCB traces underneath or adjacent to the XIN and XOUT pins.
• Use assembly materials and processes that avoid any parasitic load on the oscillator XIN and XOUT pins.
• If conformal coating is used, make sure that it does not induce capacitive or resistive leakage between the oscillator pins.
(2) When LFXTBYPASS is set, LFXT circuits are automatically powered down. Input signal is a digital square wave with parametrics
defined in the Schmitt-trigger inputs section of this data sheet. Duty cycle requirements are defined by DC_{LFXT, SW}.
(3) Maximum frequency of operation of the entire device cannot be exceeded.
(4) Oscillation allowance is based on a safety factor of 5 for recommended crystals. The oscillation allowance is a function of the
LFXTDRIVE settings and the effective load. In general, comparable oscillator allowance can be achieved based on the following
guidelines, but should be evaluated based on the actual crystal selected for the application:
• For LFXTDRIVE = {0}, C_L,eff = 3.7 pF.
• For LFXTDRIVE = {1}, 6 pF ≤ C_L,eff ≤ 9 pF.
• For LFXTDRIVE = {2}, 6 pF ≤ C_L,eff ≤ 10 pF.
• For LFXTDRIVE = {3}, 6 pF ≤ C_L,eff ≤ 12 pF.
(5) Includes parasitic bond and package capacitance (approximately 2 pF per pin).
(6) Requires external capacitors at both terminals. Values are specified by crystal manufacturers.
(7) Includes start-up counter of 1024 clock cycles.
(8) Frequencies above the MAX specification do not set the fault flag. Frequencies in between the MIN and MAX specification may set the
flag. A static condition or stuck at fault condition sets the flag.
(9) Measured with logic-level input frequency but also applies to operation with crystals.
18
Specifications
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