ACE5372

Low Power Real-Time Clock (RTC)

VER 1.3

20

The user shall always be able to access the real-time clock as long as the following two conditions are

met.

1) No stop condition shall be generated until clock read/write is started and completed.

2) One cycle read/write operation shall be completed within 0.5 seconds.

Bad example of reading from seconds to hours (invalid read)

(Start condition) → (Read of seconds) → (Read of minutes) → (Stop condition) → (Start condition) →

(Read of hour) → (Stop condition)

Assuming read was started at 09:59:59PM, and while reading seconds and minutes the time

advanced to 10:00:00 PM. At this time second digit is hold so the read as 59:59. ACE5372

confirms (Stop condition) and carry second digit being hold and the time changes to 10:00:00 PM.

Then, when the hour digit is read, it changes to 10. The wrong results of 10:59:59 will be read.

Configuration of Oscillating Circuit and Time Trimming Circuit

a)In general crystal oscillators are classified by their central frequency of CL (load capacitance) and

available further grouped in several ranks as ±10，±20 and ±50ppm of fluctuations in precision.

b)The fluctuation of IC circuit frequency is ±5~10ppm at room temperature.

c)Here, the clock accuracy at room temperature varies along with the variation of the characteristic of

crystal oscillator.

Configuration of Oscillating Circuit

Because the adjustment of crystal oscillator frequency is also the adjustment of clock frequency, so the

If crystal oscillator frequency is on the higher side, the CL should be decreased, contrarily, the CL should

be increased.

Cs

Cout

Cin

Cout

Cin

Cl







*