Datasheet

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MSP432P401R, MSP432P401M
www.ti.com SLAS826 –MARCH 2015
Table 5-18. Low-Frequency Crystal Oscillator, LFXT
over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted)
PARAMETER TEST CONDITIONS V
CC
MIN TYP MAX UNIT
f
OSC
= 32.768 kHz
LFXTBYPASS = 0, LFXTDRIVE = {0},
3.0 V 100
C
L,eff
= 3.7 pF
Typical ESR, C
SHUNT
f
OSC
= 32.768 kHz
LFXTBYPASS = 0, LFXTDRIVE = {1},
3.0 V 200
C
L,eff
= 6 pF
Typical ESR, C
SHUNT
I
VCC,LFXT
Current consumption
(1)
f
OSC
= 32.768 kHz
LFXTBYPASS = 0, LFXTDRIVE = {2},
3.0 V 300 nA
C
L,eff
= 9 pF,
Typical ESR, C
SHUNT
f
OSC
= 32.768 kHz
LFXTBYPASS = 0, LFXTDRIVE = {3},
3.0 V 500
C
L,eff
= 12 pF,
Typical ESR, C
SHUNT
f
LFXT
LFXT oscillator crystal frequency LFXTBYPASS = 0
(2)
32.768 kHz
DC
LFXT
LFXT oscillator duty cycle f
LFXT
= 32.768 kHz
(2)
30% 70%
LFXT oscillator logic-level square-
f
LFXT,SW
LFXTBYPASS = 1
(3) (4)
10 32.768 50 kHz
wave input frequency
DC
LFXT,
LFXT oscillator logic-level square-
LFXTBYPASS = 1 30% 70%
SW
wave input duty cycle
LFXTBYPASS = 0, LFXTDRIVE =
{1}, TBD
f
LFXT
= 32.768 kHz, C
L,eff
= 6 pF
Oscillation allowance for
OA
LFXT
kΩ
LF crystals
(5)
LFXTBYPASS = 0, LFXTDRIVE =
{3}, 300
f
LFXT
= 32.768 kHz, C
L,eff
= 12 pF
Integrated effective load
C
L,eff
1 pF
capacitance
(6) (7)
f
OSC
= 32.768 kHz
LFXTBYPASS = 0, LFXTDRIVE = {0},
C
L,eff
= 3.7 pF 0.6
Typical ESR, C
SHUNT
FCNTLF_EN = 0
(2)
t
START,LFXT
Start-up time
(8)
3.0 V s
f
OSC
= 32.768 kHz
LFXTBYPASS = 0, LFXTDRIVE = {3},
C
L,eff
= 12 pF 2
Typical ESR, C
SHUNT
FCNTLF_EN = 0
(2)
f
Fault,LFXT
Oscillator fault frequency
(9) (10)
1 8 kHz
(1) Total current measured on both AVCC and DVCC supplies.
(2) Measured at ACLK pin.
(3) When LFXTBYPASS is set, LFXT circuits are automatically powered down. Input signal is a digital square wave with parametrics
defined in the Schmitt-trigger Inputs section of this datasheet. Duty cycle requirements are defined by DC
LFXT, SW
.
(4) Maximum frequency of operation of the entire device cannot be exceeded.
(5) Oscillation allowance is based on a safety factor of 5 for recommended crystals. The oscillation allowance is a function of the
LFXTDRIVE settings and the effective load. In general, comparable oscillator allowance can be achieved based on the following
guidelines, but should be evaluated based on the actual crystal selected for the application:
• For LFXTDRIVE = {0}, C
L,eff
= 3.7 pF.
• For LFXTDRIVE = {1}, 6 pF ≤ C
L,eff
≤ 9 pF.
• For LFXTDRIVE = {2}, 6 pF ≤ C
L,eff
≤ 10 pF.
• For LFXTDRIVE = {3}, 6 pF ≤ C
L,eff
≤ 12 pF.
(6) Includes parasitic bond and package capacitance (approximately 2 pF per pin).
(7) Requires external capacitors at both terminals. Values are specified by crystal manufacturers. Recommended values supported are
3.7 pF, 6 pF, 9 pF, and 12 pF. Maximum shunt capacitance of 1.6 pF. Because the PCB adds additional capacitance, it must be
considered, and TI recommends verifying proper oscillator performance.
(8) Does not include programmable startup counter.
(9) Frequencies above the MAX specification do not set the fault flag. Frequencies in between the MIN and MAX specification may set the
flag. A static condition or stuck at fault condition will set the fault flag.
(10) Measured with logic-level input frequency but also applies to operation with crystals.
Copyright © 2015, Texas Instruments Incorporated Specifications 29
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