CR2032 RTC BATTERY WIDELY USED IN LAPTOP AND DESKTOP PC.

                           Though RTCVCC is having one another power source from 3V LDO also that when main battery or power adapter plugged than it bypass the RTC/CMOS Battery power and thereby doubling the time need to replace it. Now a days most internal Battery are having CMOS power pin also.

                            But in a coin-cell battery ( model ) CR2032 powers the real-time clock and CMOS memory. When the computer

is not plugged into a wall socket, the battery has an estimated life of three years. When the

computer is plugged in, the standby current from the power supply extends the life of the battery.

                           The RTC clock is accurate to ± 13 minutes/year at 25 ºC with 3.3 VSB applied via the power supply chip LDO Pin or STBY rail.

Generally used CR2032 Battery has rated capacity of 225mAH.

So if a Main boards RTC section consumes average 6uA current for CMOS Memory and RTC chip circuit we can calculate estimated life.3

HOW TO MEASURE CMOS CURRENT CONSUMED BY THE BOARD.

                            How much time will it lost?

                            Before calculate we are having assumptions:

                           * Constant Current Draw: The RTC's current consumption remains constant at 6 uA throughout the battery's discharge cycle.

                           * Ideal Battery: The CR2032 battery's capacity remains constant at 225 mAh until it is completely depleted.

                           * No Other Loads: The battery solely powers the RTC, and there are no other significant current drains.

                           Calculations:

* Convert Battery Capacity:

* 225 mAh = 225 * 1000 uAh = 225000 uAh

* Calculate Battery Life:

* Battery Life (hours) = Battery Capacity (uAh) / Current Consumption (uA)

* Battery Life = 225000 uAh / 6 uA = 37500 hours

* Convert to Years:

* Battery Life (years) = 37500 hours / 8760 hours/year ≈ 4.28 years

                            Under the given assumptions, the CR2032 battery should theoretically power the RTC section for approximately 4.28 years.

Additional Considerations:

                            * Practical Battery Life: In reality, battery life may be shorter due to factors like self-discharge, temperature variations, and non-ideal battery behavior. Mind laptop mainboard having a bi-diode with series resistor and another diode carry power from 3.3V source disabling load on CR2032 itself and in turn increase battery life.

                             * RTC Current Consumption: The RTC's current consumption can vary depending on its specific design and operating conditions.

                              * Other Loads: If the battery powers other components or circuits e.g.Power on Switch, EC VBAT PIN , the overall battery life will be reduced.Boards RTC section drastically affected by moisture contamination and thereby PF leakages.

                              * When the voltage drops below a certain level, the BIOS Setup program settings stored in CMOS

RAM (for example, the date and time) might not be accurate. Replace the battery with an

equivalent one.

                               * System can power on from G3/AC power loss state without the Real-Time Clock battery.

By understanding these factors, you can make more accurate predictions about the battery life in your specific application.

HISTORY

Example Chip : DS12C887

                                 IBM PC USE THIS CHIP BUT NOW A DAYS IT HAS INTEGRAED TO PCH AND SOC SO ON.

                               FEATURES

                                 ♦ Drop-In Replacement for IBM AT Computer Clock/Calendar

                                 ♦ RTC Counts Seconds, Minutes, Hours, Day, Date, Month, and Year with Leap Year Compensation Through 2099

                                 ♦ Binary or BCD Time Representation

                                 ♦ 12-Hour or 24-Hour Clock with AM and PM in 12-Hour Mode

                                 ♦ Daylight Saving Time Option

                                 ♦ Selectable Intel or Motorola Bus Timing

                                 ♦ Interfaced with Software as 128 RAM Locations

                                 ♦ 14 Bytes of Clock and Control Registers

                                 ♦ 114 Bytes of General-Purpose, Battery-Backed RAM (113 Bytes in the DS12C887 and DS12C887A)

                                 ♦ RAM Clear Function (DS12885, DS12887A, and DS12C887A)

                                 ♦RTC Counts Seconds, Minutes, Hours, Day, Date, Month, and Year with Leap Year Compensation Through 2099.

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