Does the CY14B108M-ZSP25XI need battery when I use for nvSRAM?
The CY14B108M-ZSP25XI is an 8Mbit nvSRAM with RTC and so has two functions - nvSRAM and RTC
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The nvSRAM does not require battery. The RTC oscillator needs a back up power source to keep it running when Vcc power is removed. This source could be a battery or a Supercap. Pl see the explanation below.
1) nvSRAM does not require battery
- When power fails, SRAM data is stored in NV cells using the charge from the VCAP capacitor. When power is applied again, the NV data is recalled to the SRAM. So no battery power for nvSRAM.
2) RTC oscillator needs a battery or a Supercap to provide back up power to keep the crystal oscillator running and to power a tick counter (which keeps the pulse count) when Vcc power fails.
- This can be done with a battery. You can use a 3V Lithium battery (coin cell).
- Alternatively, you can use a supercap. The supercap will be charged during Vcc power and the stored charge in the capacitor will power the RTC oscillator when Vcc power fails.
- Switching to back up power from Vcc power happens automatically when Vcc fails. Also, switching back to Vcc power happens automatically when power is restored.
In summary, the 8Mbit nvSRAM does not need battery in case you are not planning to use the real time clock feature in the CY14B108M-ZSP25XI. If using RTC, you need a battery or a Supercap to supply power to the RTC oscillator circuit - which consumes less than 0.5uA (IBAK current) to operate - when Vcc power is removed.
nvSRAM does not need battery. It needs the VCAP capacitor to store data to the NV cells when power fails.
RTC circuit needs battery at the VRTCbat pin (or a supercap at the VRTCcap pin) to give power to the RTC oscillator circuit when the VCC power fails. If a battery (or supercap) is not connected, then the crystal oscillator would stop when VCC power is lost. On the next power up, the RTC time keeping registers will revert to the base time which is the time you set initially by writing into the RTC registers.