MSP430F249-EP_014 Datasheet, PDF (43/81 Pages) Texas Instruments – MIXED SIGNAL MICROCONTROLLER

MSP430F249-EP
MIXED SIGNAL MICROCONTROLLER
2008
electrical characteristics over recommended ranges of supply voltage and operating free-air
temperature (unless otherwise noted) (continued)
crystal oscillator, LFXT1, high frequency modes (see Note 5 and 6)
PARAMETER
TEST CONDITIONS
VCC
MIN TYP MAX UNIT
f_LFXT1,HF0
LFXT1 oscillator crystal frequency,
HF mode 0
XTS = 1, LFXT1Sx = 0, XCAPx = 0
1.8 V to 3.6 V
0.4
1 MHz
f_LFXT1,HF1
LFXT1 oscillator crystal frequency,
HF mode 1
XTS = 1, LFXT1Sx = 1, XCAPx = 0
1.8 V to 3.6 V
1
4 MHz
1.8 V to 3.6 V
2
f_LFXT1,HF2
LFXT1 oscillator crystal frequency,
HF mode 2
XTS = 1, LFXT1Sx = 2, XCAPx = 0
2.2 V to 3.6 V
2
3 V to 3.6 V
2
10
12 MHz
16
1.8 V to 3.6 V 0.4
LFXT1 oscillator logic level square
f_{LFXT1,HF,logic wave input frequency, HF mode}
XTS = 1, LFXT1Sx = 3, XCAPx = 0
2.2 V to 3.6 V
0.4
3 V to 3.6 V
0.4
10
12 MHz
16
OA_HF
C_L,eff
Oscillation Allowance for HF
crystals
(refer to Figure 23 and Figure 24)
Integrated effective load
capacitance, HF mode
XTS = 1, XCAPx = 0, LFXT1Sx = 0,
f_LFXT1,HF = 1 MHz,
C_L,eff = 15 pF
XTS = 1, XCAPx = 0, LFXT1Sx = 1
f_LFXT1,HF = 4 MHz,
C_L,eff = 15 pF
XTS = 1, XCAPx = 0, LFXT1Sx = 2
f_LFXT1,HF = 16 MHz,
C_L,eff = 15 pF
XTS = 1, XCAPx = 0 (see Note 2)
2700
800
W
300
1
pF
Duty cycle HF mode
f_Fault,HF
Oscillator fault frequency, HF
mode (see Note 4)
XTS = 1, XCAPx = 0, Measured at
P1.4/SMCLK, f_LFXT1,HF = 10 MHz
XTS = 1, XCAPx = 0, Measured at
P1.4/SMCLK, f_LFXT1,HF = 16 MHz
XTS = 1, LFXT1Sx = 3, XCAPx = 0
(see Notes 3)
2.2 V/3 V
2.2 V/3 V
40
50
60
%
40
50
60
30
300 kHz
NOTES:
1. 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.
2. Requires external capacitors at both terminals. Values are specified by crystal manufacturers.
3. Measured with logic level input frequency but also applies to operation with crystals.
4. Frequencies below the MIN specification will set the fault flag, frequencies above the MAX specification will not set the fault flag.
Frequencies in between might set the flag.
5. To improve EMI on the LFXT1 oscillator the following guidelines should be observed.
− 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 praxis to avoid any parasitic load on the oscillator XIN and XOUT pins.
− If conformal coating is used, ensure that it does not induce capacitive/resistive leakage between the oscillator pins.
− 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.
6. For T_a > 105°C: Applies only if an external logic−lvel clock source is used. Not applicable when using a crystal or a resonator.
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