MSP430F6776IPZ datasheet(65/157 Pages) TI

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MSP430F677x

MSP430F676x

MSP430F674x

www.ti.com

SLAS768C – SEPTEMBER 2012 – REVISED APRIL 2013

Crystal Oscillator, XT1, Low-Frequency Mode

(1)

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

PARAMETER

TEST CONDITIONS

VCC

MIN

TYP

MAX

UNIT

fOSC = 32768 Hz, XTS = 0, XT1BYPASS = 0,

0.075

XT1DRIVEx = 1, TA = 25°C

Differential XT1 oscillator

crystal current consumption

fOSC = 32768 Hz, XTS = 0, XT1BYPASS = 0,

ΔIDVCC.LF

3 V

0.170

µA

from lowest drive setting, LF

XT1DRIVEx = 2, TA = 25°C

mode

fOSC = 32768 Hz, XTS = 0, XT1BYPASS = 0,

0.290

XT1DRIVEx = 3, TA = 25°C

XT1 oscillator crystal

fXT1,LF0

XTS = 0, XT1BYPASS = 0

32768

frequency, LF mode

XT1 oscillator logic-level

fXT1,LF,SW

square-wave input frequency, XTS = 0, XT1BYPASS = 1(2) (3)

32.768

kHz

LF mode

XTS = 0, XT1BYPASS = 0, XT1DRIVEx = 0,

210

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

Oscillation allowance for

OALF

Ω

LF crystals(4)

XTS = 0, XT1BYPASS = 0, XT1DRIVEx = 1,

300

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

XTS = 0, XCAPx = 0(6)

XTS = 0, XCAPx = 1

5.5

Integrated effective load

CL,eff

capacitance, LF mode(5)

XTS = 0, XCAPx = 2

8.5

XTS = 0, XCAPx = 3

12.0

XTS = 0, Measured at ACLK,

Duty cycle, LF mode

fXT1,LF = 32768 Hz

Oscillator fault frequency,

fFault,LF

XTS = 0(8)

10000

LF mode(7)

fOSC = 32768 Hz, XTS = 0, XT1BYPASS = 0,

1000

XT1DRIVEx = 0, TA = 25°C, CL,eff = 6 pF

tSTART,LF

Startup time, LF mode

3 V

fOSC = 32768 Hz, XTS = 0, XT1BYPASS = 0,

500

XT1DRIVEx = 3, TA = 25°C, CL,eff = 12 pF

(1)

To improve EMI on the XT1 oscillator, the following guidelines should be observed.

(a) Keep the trace between the device and the crystal as short as possible.

(b) Design a good ground plane around the oscillator pins.

(d) Avoid running PCB traces underneath or adjacent to the XIN and XOUT pins.

(e) Use assembly materials and praxis to avoid any parasitic load on the oscillator XIN and XOUT pins.

(f) If conformal coating is used, ensure that it does not induce capacitive or resistive leakage between the oscillator pins.

(2)

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

the Schmitt-trigger Inputs section of this data sheet.

(3)

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

(4)

Oscillation allowance is based on a safety factor of 5 for recommended crystals. The oscillation allowance is a function of the

XT1DRIVEx 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:

(a) For XT1DRIVEx = 0, CL,eff ≤ 6 pF.

(b) For XT1DRIVEx = 1, 6 pF

≤ CL,eff ≤ 9 pF.

≤ CL,eff ≤ 10 pF.

(d) For XT1DRIVEx = 3, CL,eff ≥ 6 pF.

(5)

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 specification of the used crystal.

(6)

Requires external capacitors at both terminals. Values are specified by crystal manufacturers.

(7)

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.

(8)

Measured with logic-level input frequency but also applies to operation with crystals.

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