The CY14B104K NvSRAM Backup Power

[Anonymous]

The CY14B104K NvSRAM Backup Power section notes that

"If a battery is applied to VRTCbat pin prior to VCC, the chip will draw high IBAK current. This occurs even if the oscillator is disabled. In order to maximize battery life, VCC must be applied before a battery is applied to VRTCbat pin."

What is the IBAK current drawn during this condition ?

Is the High IBAK current, instantaneous or steady state current for this condition?

When a battery is used instead of a capacitor as back up power source, the VRTCbat will always have a potential applied before VCC is applied during power cycle. How does this affect the battery backup ?

Regards,

Supreeth

[PradiptaB_11 · Accepted solution]

Hi Supreeth,

There can be a huge impact on IBAK when disconnecting and reconnecting the RTC backup power source (battery or Supercap) without main (VCC) power is ON. When the nvSRAM RTC device switches from the main power to the backup power, it internally switches the RTC circuit configuration from HPM (High Power Mode) to LPM (Low Power Mode) to ensure that the oscillation continues with minimum circuitry ON to keep IBAK minimum( you will observe this value within the datasheet specifications). When the battery is removed in LPM, the device LPM configuration is lost and when the battery is reconnected, the RTC circuit starts getting the power supply, but the state of the circuit remains unknown and it can be LPM,  HPM or any other undefined state. Any state other than LPM will draw more IBAK current.

Thanks and Regards,

Pradipta.