Datasheet

ECCN 5E002 TSPA - Technology / Software Publicly Available
MSP430F677x , MSP430F676x , MSP430F674x
www.ti.com SLAS768D –SEPTEMBER 2012–REVISED DECEMBER 2013
Crystal Oscillator, XT1, Low-Frequency Mode
(1)
over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted)
PARAMETER TEST CONDITIONS V
CC
MIN TYP MAX UNIT
f
OSC
= 32768 Hz, XTS = 0, XT1BYPASS = 0,
0.075
XT1DRIVEx = 1, T
A
= 25°C
Differential XT1 oscillator
crystal current consumption f
OSC
= 32768 Hz, XTS = 0, XT1BYPASS = 0,
ΔI
DVCC.LF
3 V 0.170 µA
from lowest drive setting, LF XT1DRIVEx = 2, T
A
= 25°C
mode
f
OSC
= 32768 Hz, XTS = 0, XT1BYPASS = 0,
0.290
XT1DRIVEx = 3, T
A
= 25°C
XT1 oscillator crystal
f
XT1,LF0
XTS = 0, XT1BYPASS = 0 32768 Hz
frequency, LF mode
XT1 oscillator logic-level
f
XT1,LF,SW
square-wave input frequency, XTS = 0, XT1BYPASS = 1
(2) (3)
10 32.768 50 kHz
LF mode
XTS = 0, XT1BYPASS = 0, XT1DRIVEx = 0,
210
f
XT1,LF
= 32768 Hz, C
L,eff
= 6 pF
Oscillation allowance for
OA
LF
kΩ
LF crystals
(4)
XTS = 0, XT1BYPASS = 0, XT1DRIVEx = 1,
300
f
XT1,LF
= 32768 Hz, C
L,eff
= 12 pF
XTS = 0, XCAPx = 0
(6)
2
XTS = 0, XCAPx = 1 5.5
Integrated effective load
C
L,eff
pF
capacitance, LF mode
(5)
XTS = 0, XCAPx = 2 8.5
XTS = 0, XCAPx = 3 12.0
XTS = 0, Measured at ACLK,
Duty cycle, LF mode 30 70 %
f
XT1,LF
= 32768 Hz
Oscillator fault frequency,
f
Fault,LF
XTS = 0
(8)
10 10000 Hz
LF mode
(7)
f
OSC
= 32768 Hz, XTS = 0, XT1BYPASS = 0,
1000
XT1DRIVEx = 0, T
A
= 25°C, C
L,eff
= 6 pF
t
START,LF
Startup time, LF mode 3 V ms
f
OSC
= 32768 Hz, XTS = 0, XT1BYPASS = 0,
500
XT1DRIVEx = 3, T
A
= 25°C, C
L,eff
= 12 pF
(1) To improve EMI on the XT1 oscillator, the following guidelines should be observed.
(a) Keep the trace between the device and the crystal as short as possible.
(b) Design a good ground plane around the oscillator pins.
(c) Prevent crosstalk from other clock or data lines into oscillator pins XIN and XOUT.
(d) Avoid running PCB traces underneath or adjacent to the XIN and XOUT pins.
(e) Use assembly materials and techniques to avoid any parasitic load on the oscillator XIN and XOUT pins.
(f) If conformal coating is used, make sure that it does not induce capacitive or resistive leakage between the oscillator pins.
(2) When XT1BYPASS is set, XT1 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.
(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
XT1DRIVEx 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:
(a) For XT1DRIVEx = 0, C
L,eff
≤ 6 pF.
(b) For XT1DRIVEx = 1, 6 pF ≤ C
L,eff
≤ 9 pF.
(c) For XT1DRIVEx = 2, 6 pF ≤ C
L,eff
≤ 10 pF.
(d) For XT1DRIVEx = 3, C
L,eff
≥ 6 pF.
(5) Includes parasitic bond and package capacitance (approximately 2 pF per pin).
Since the PCB adds additional capacitance, it is recommended to verify the correct load by measuring the ACLK frequency. For a
correct setup, the effective load capacitance should always match the specification of the used crystal.
(6) Requires external capacitors at both terminals. Values are specified by crystal manufacturers.
(7) Frequencies below the MIN specification set the fault flag. Frequencies above the MAX specification do not set the fault flag.
Frequencies in between might set the flag.
(8) Measured with logic-level input frequency but also applies to operation with crystals.
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