Datasheet

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SLAS439A − SEPTEMBER 2004 − REVISED JUNE 2005
26
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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)
PARAMETER TEST CONDITIONS VCC MIN TYP MAX UNIT
f
LFXT1,HF0
LFXT1 oscillator crystal frequency,
HF mode 0
XTS = 1, LFXT1Sx = 0 1.8 V − 3.6 V 0.4 1 MHz
f
LFXT1,HF1
LFXT1 oscillator crystal frequency,
HF mode 1
XTS = 1, LFXT1Sx = 1 1.8 V − 3.6 V 1 4 MHz
LFXT1 oscillator crystal frequency,
1.8 V − 3.6 V 2 10 MHz
f
LFXT1,HF2
LFXT1 oscillator crystal frequency,
HF mode 2
XTS = 1, LFXT1Sx = 2
2.2 V − 3.6 V 2 12 MHz
f
LFXT1,HF2
HF mode 2
XTS = 1, LFXT1Sx = 2
3.0 V − 3.6 V 2 16 MHz
LFXT1 oscillator logic level square
1.8 V − 3.6 V 0.4 10 MHz
f
LFXT1,HF,logic
LFXT1 oscillator logic level square
wave input frequency,
HF mode
XTS = 1, LFXT1Sx = 3
2.2 V − 3.6 V 0.4 12 MHz
f
LFXT1,HF,logic
wave input frequency,
HF mode
XTS = 1, LFXT1Sx = 3
3.0 V − 3.6 V 0.4 16 MHz
XTS = 0, LFXT1Sx = 0,
f
LFXT1,HF
= 1 MHz,
C
L,eff
= 15 pF
2700 W
OA
HF
Oscillation Allowance for HF
crystals
(refer to Figure 14 and Figure 15)
XTS = 0, LFXT1Sx = 1
f
LFXT1,HF
= 4 MHz,
C
L,eff
= 15 pF
800 W
(refer to Figure 14 and Figure 15)
XTS = 0, LFXT1Sx = 2
f
LFXT1,HF
= 16 MHz,
C
L,eff
= 15 pF
300 W
C
L,eff
Integrated effective Load
Capacitance, HF mode
(see Note 1)
XTS = 1 (see Note 2) 1 pF
Duty Cycle
HF mode
XTS = 1, Measured at P1.4/ACLK,
f
LFXT1,HF
= 10 MHz
2.2 V/3 V 40 50 60 %
Duty Cycle
HF mode
XTS = 1, Measured at P1.4/ACLK,
f
LFXT1,HF
= 16 MHz
2.2 V/3 V 40 50 60 %
f
Fault,HF
Oscillator fault frequency, HF mode
(see Note 4)
XTS = 1, LFXT1Sx = 3
(see Notes 3)
2.2 V/3 V 30 300 kHz
NOTES: 1. Includes parasitic bond and package capacitance (approximately 2pF 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 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.