Datasheet

MSP430FW42x
www.ti.com SLAS383D –OCTOBER 2003–REVISED JANUARY 2011
Crystal Oscillator, LFXT1 Oscillator
(1) (2)
over recommended operating free-air temperature range (unless otherwise noted)
PARAMETER TEST CONDITIONS V
CC
MIN TYP MAX UNIT
OSCCAPx = 0h 0
OSCCAPx = 1h 10
C
XIN
Integrated input capacitance
(3)
2.2 V/3 V pF
OSCCAPx = 2h 14
OSCCAPx = 3h 18
OSCCAPx = 0h 0
OSCCAPx = 1h 10
C
XOUT
Integrated output capacitance
(3)
2.2 V/3 V pF
OSCCAPx = 2h 14
OSCCAPx = 3h 18
V
IL
V
SS
0.2 × V
CC
Input levels at XIN
(4)
2.2 V/3 V V
V
IH
0.8 × V
CC
V
CC
(1) The parasitic capacitance from the package and board may be estimated to be 2 pF. The effective load capacitor for the crystal is (C
XIN
× C
XOUT
) / (C
XIN
+ C
XOUT
). This is independent of XTS_FLL.
(2) To improve EMI on the low-power LFXT1 oscillator, particularly in the LF mode (32 kHz), 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 praxis to avoid any parasitic load on the oscillator XIN and XOUT pins.
(f) If conformal coating is used, ensure that it does not induce capacitive/resistive leakage between the oscillator pins.
(g) Do not route the XOUT line to the JTAG header to support the serial programming adapter as shown in other documentation. This
signal is no longer required for the serial programming adapter.
(3) External capacitance is recommended for precision real-time clock applications; OSCCAPx = 0h.
(4) Applies only when using an external logic-level clock source. XTS_FLL must be set. Not applicable when using a crystal or resonator.
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