msp430f2121irge Microchip Technology Inc., msp430f2121irge Datasheet - Page 26

• Manufacturer Part Number: msp430f2121irge
• Description: Msp430
• Manufacturer: Microchip Technology Inc.

MSP430x21x1
MIXED SIGNAL MICROCONTROLLER
SLAS439C − SEPTEMBER 2004 − REVISED JULY 2006
electrical characteristics over recommended ranges of supply voltage and operating free-air
temperature (unless otherwise noted) (continued)
crystal oscillator, LFXT1, low frequency modes (see Note 4)
NOTES: 1. Includes parasitic bond and package capacitance (approximately 2pF per pin).
26
f LFXT1,LF
f LFXT1,LF,logic
OA LF
OA LF
C L,eff
C L,eff
Duty Cycle
f Fault,LF
2. Measured with logic level input frequency but also applies to operation with crystals.
3. Frequencies below the MIN specification will set the fault flag, frequencies above the MAX specification will not set the fault flag.
4. To improve EMI on the LFXT1 oscillator the following guidelines should be observed.
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.
Frequencies in between might set the flag.
−
−
−
−
−
−
−
LFXT1 oscillator crystal
frequency, LF mode 0, 1
LFXT1 oscillator logic level
square wave input frequency,
LF mode
Oscillation Allowance for LF
Oscillation Allowance for LF
crystals
Integrated effective Load
Integrated effective Load
Capacitance, LF mode
Capacitance, LF mode
(see Note 1)
(see Note 1)
LF mode
Oscillator fault frequency, LF
mode (see Note 3)
Keep as short of a trace as possible between the device and the crystal.
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.
PARAMETER
POST OFFICE BOX 655303
XTS = 0, LFXT1Sx = 0 or 1
XTS = 0, LFXT1Sx = 3
XTS = 0, LFXT1Sx = 0;
f LFXT1,LF = 32,768 kHz,
C L,eff = 6 pF
XTS = 0, LFXT1Sx = 0;
f LFXT1,LF = 32,768 kHz,
C L,eff = 12 pF
XTS = 0, XCAPx = 0
XTS = 0, XCAPx = 1
XTS = 0, XCAPx = 2
XTS = 0, XCAPx = 3
XTS = 0, Measured at
P1.4/ACLK, f LFXT1,LF = 32,768
Hz
XTS = 0, LFXT1Sx = 3
(see Notes 2)
TEST CONDITIONS
•
DALLAS, TEXAS 75265
1.8 V − 3.6 V
1.8 V − 3.6 V
2.2 V/3 V
2.2 V/3 V
VCC
10,000
MIN
30
10
32,768
32,768
TYP
500
200
5.5
8.5
11
50
1
50,000
10,000
MAX
70
UNIT
Hz
Hz
kW
kW
pF
pF
pF
pF
Hz
%