Datasheet

MSP430F471x3, MSP430F471x6, MSP430F471x7
MIXED SIGNAL MICROCONTROLLER
SLAS626C -- OCTOBER 2008 -- REVISED MARCH 2011
42
POST OFFICE BOX 655303  DALLAS, TEXAS 75265
electrical characteristics over recommended operating free-air temperature (unless otherwise
noted) (continued)
crystal oscillator, LFXT1, low-frequency mode (see Note 4)
PARAMETER TEST CONDITIONS V
CC
MIN TYP MAX UNIT
f
LFXT1,LF
LFXT1 oscillator crystal
frequency, LF mode
XTS = 0 1.8 V to 3.6 V 32768 Hz
O
A
Oscillation allowance
f
or LF
XTS = 0, LFXT1Sx = 0,
f
LFXT1,LF
= 32768 Hz,
C
L,eff
=6pF
500 kΩ
O
A
LF
O
s
c
i
l
l
a
t
i
o
n
a
l
l
o
w
a
n
c
e
f
o
r
L
F
crystals
XTS = 0, LFXT1Sx = 0,
f
LFXT1,LF
= 32768 Hz,
C
L,eff
=12pF
200 kΩ
XTS = 0, XCAPxPF = 0 1 pF
C
Integrated effective load
c
a
p
a
c
i
t
a
n
c
e
L
F
m
o
d
e
XTS = 0, XCAPxPF = 1 5.5 pF
C
L,eff
capacitance, LF mode
(
s
e
e
N
o
t
e
1
)
XTS = 0, XCAPxPF = 2 8.5 pF
(
s
e
e
N
o
t
e
1
)
XTS = 0, XCAPxPF = 3 11 pF
Duty Cycle LF mode
XTS = 0, f
LFXT1,LF
= 32768 Hz
Measured at P1.5/TACLK/ACLK
2.2 V/3 V 30 50 70 %
f
Fault,LF
Oscillator fault frequency,
LF mode (see Note 3)
XTS=0(seeNote2) 2.2 V/3 V 10 10,000 Hz
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 s pecification of the used crystal.
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.
Frequencies in between might set the flag.
4. 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.
crystal oscillator, LFXT1, high-frequency mode
PARAMETER TEST CONDITIONS V
CC
MIN TYP MAX UNIT
f
XT1
XT1 oscillator crystal frequency XTS = 1, Ceramic resonator 1.8 V to 3.6 V 0.45 6 MHz
f
XT1
XT1 oscillator crystal frequency XTS = 1, Crystal 1.8 V to 3.6 V 1 6 MHz
C
L,eff
Integrated effective load
capacitance (see Note 1)
(see Note 2) 1 pF
Duty Cycle Measured at P1.5/TACLK/ACLK 2.2 V/3 V 40 50 60 %
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 s pecification of the used crystal.
2. Requires external capacitors at both terminals. Values are specified by crystal manufacturers.