AB18X5 Real-Time Clock with Power

Management Family

Date of Issue: October 16, 2014

3.0 x 3.0 mm

Page 14 of 37

Abracon Drawing #453568

Revision: C

5.4 Oscillator Parameters

Table 7 lists the oscillator parameters.

Table 7: Oscillator Parameters

SYMBOL

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

XI and XO pin Crystal Fre-

quency

32.768

kHz

XT Oscillator failure detection

frequency

8kHz

Internal XI and XO pin capac-

itance

1pF

External XI and XO pin PCB

capacitance

1pF

XT Oscillation Allowance

At 25°C using a 32.768 kHz

crystal

270

320

kΩ

Calibrated RC Oscillator Fre-

Factory Calibrated at 25°C,

VCC = 2.8V

128

Hz

Uncalibrated RC Oscillator

Frequency

Calibration Disabled (OFF-

SETR = 0)

89

122

220

Hz

RC Oscillator cycle-to-cycle

jitter

Calibration Disabled (OFF-

SETR = 0) – 128 Hz

2000

ppm

Calibration Disabled (OFF-

SETR = 0) – 1 Hz

500

XT mode digital calibration

Calibrated at an initial tem-

perature and voltage

-2

2

ppm

Autocalibration mode timing

accuracy, 512 second period,

24 hour run time

35

ppm

1 week run time

20

1 month run time

10

1 year run time

3

Autocalibration mode operat-

-10

60

°C

32.768 kHz tuning fork crystal has a negative temperature coefficient with a parabolic frequency deviation, which due to

the crystal alone can result in a change of up to 150 ppm across the entire operating temperature range of -40°C to 85°C

in XT mode. Autocalibration mode timing accuracy is specified relative to XT mode timing accuracy from -10°C to 60°C.

RC digital calibration range (+/-12%) for autocalibration mode.If this happens, an autocalibration failure will occur and the

ACF interrupt flag is set. The AB18X5 should be switched to use the XT oscillator as its clock source. Please see the

Autocalibration Fail section for more details.