MSP430F6638IPZ datasheet(29/133 Pages) TI

29 / 133 page

8.16 Crystal Oscillator, XT1, Low-Frequency Mode

over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted)(5)

PARAMETER

TEST CONDITIONS

VCC

MIN

TYP

MAX UNIT

ΔIDVCC,LF

Differential XT1 oscillator crystal

current consumption from lowest

drive setting, LF mode

fOSC = 32768 Hz, XTS = 0,

XT1BYPASS = 0, XT1DRIVEx = 1,

TA = 25°C

3 V

0.075

µA

fOSC = 32768 Hz, XTS = 0,

XT1BYPASS = 0, XT1DRIVEx = 2,

TA = 25°C

0.170

fOSC = 32768 Hz, XTS = 0,

XT1BYPASS = 0, XT1DRIVEx = 3,

TA = 25°C

0.290

fXT1,LF0

XT1 oscillator crystal frequency,

LF mode

XTS = 0, XT1BYPASS = 0

32768

fXT1,LF,SW

XT1 oscillator logic-level square-

wave input frequency, LF mode

XTS = 0, XT1BYPASS = 1(6) (7)

32.768

kHz

OALF

Oscillation allowance for

LF crystals(8)

XTS = 0,

XT1BYPASS = 0, XT1DRIVEx = 0,

fXT1,LF = 32768 Hz, CL,eff = 6 pF

210

kΩ

XTS = 0,

XT1BYPASS = 0, XT1DRIVEx = 1,

fXT1,LF = 32768 Hz, CL,eff = 12 pF

300

CL,eff

Integrated effective load

capacitance, LF mode(1)

XTS = 0, XCAPx = 0(2)

XTS = 0, XCAPx = 1

5.5

XTS = 0, XCAPx = 2

8.5

XTS = 0, XCAPx = 3

12.0

Duty cycle, LF mode

XTS = 0, Measured at ACLK,

fXT1,LF = 32768 Hz

30%

70%

fFault,LF

Oscillator fault frequency,

LF mode(4)

XTS = 0(3)

10000

tSTART,LF

Start-up time, LF mode

fOSC = 32768 Hz, XTS = 0,

XT1BYPASS = 0, XT1DRIVEx = 0,

TA = 25°C,

CL,eff = 6 pF

3 V

1000

fOSC = 32768 Hz, XTS = 0,

XT1BYPASS = 0, XT1DRIVEx = 3,

TA = 25°C,

CL,eff = 12 pF

500

(1)

Includes parasitic bond and package capacitance (approximately 2 pF per pin).

Because the PCB adds additional capacitance, TI recommends verifying 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 set the fault flag. Frequencies above the MAX specification do not set the fault flag.

Frequencies in between might set the flag.

(5)

To improve EMI on the XT1 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 processes that avoid any parasitic load on the oscillator XIN and XOUT pins.

•

If conformal coating is used, make sure that it does not induce capacitive or resistive leakage between the oscillator pins.

(6)

When XT1BYPASS is set, XT1 circuit is automatically powered down. Input signal is a digital square wave with parametrics defined in

the Schmitt-trigger Inputs section of this datasheet.

(7)

Maximum frequency of operation of the entire device cannot be exceeded.

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MSP430F6638, MSP430F6637, MSP430F6636, MSP430F6635, MSP430F6634

MSP430F6633, MSP430F6632, MSP430F6631, MSP430F6630

SLAS566G – JUNE 2010 – REVISED SEPTEMBER 2020

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MSP430F6638IPZ Datasheet(PDF) 29 Page - Texas Instruments

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