Power Management Data Storage Device Selection

zbz0529

Power Management Data Storage Device Selection [Copy link]

In data acquisition, data storage chips generally include RAM, E2PROM, FLASH and NVRAM. The following is a comparison of their advantages and disadvantages.
(1) RAM (such as 62256, etc.) is also called random read and write memory. Its advantages are short read and write time (nsec level) and can be read and written randomly by byte. It is frequently used in systems with large data read and write volumes. Its disadvantage is that the data stored in it will be lost after power failure, so RAM is often used to temporarily store intermediate data rather than to save the final result.
(2) E2PROM (such as 2816, etc.) is called electrically erasable programmable read-only memory. The parallel E2PROM pin package is fully compatible with RAM of the same capacity and can be directly replaced. Its advantage is that it can be used as both ROM and RAM, making the design more flexible and convenient. Its disadvantage is that the data erase and write time is slow, generally at the ms level, and the number of writes to the storage unit is limited.
(3) FLASH (fast erasable memory, such as 28F256) overcomes the slow writing speed of E2PROM and reaches the writing speed of us level. It can be erased and written at least 10,000 times, so it is often used in some embedded systems to realize online programming.
(4) NVRAM (power-off non-lost data RAM, such as DS1235) not only has the advantages of RAM, but also can ensure that the data stored in it will not be lost for 10 years. When the power supply voltage is normal, NVRAM uses an external power supply, and data can be read and written at this time. When the external power supply voltage fluctuates out of the allowable range, NVRAM self-protects and prohibits reading and writing operations on it. It uses internal battery power to ensure that data is not lost. The disadvantage of NVRAM is that when the microcontroller program is interrupted during operation, the reliability of the stored data cannot be guaranteed. However, for systems with watchdogs, this probability is greatly reduced. Considering the cost of NVRAM (DS1235 is about 250 yuan), domestic chips such as BS and HK series can be used. You can also modify it yourself with RAM. The battery can use the common 3.6 V rechargeable battery on the market, so that the battery can be automatically charged when the system is running. In actual use, an appropriate resistor (usually 100 Ω) should be connected in series in the battery charging and discharging circuit. Another way is to use a capacitor instead of a battery, but the discharge time is shortened accordingly. At present, there are 1F DC capacitors, which do not require additional circuits for charging and discharging, which is quite convenient. Since the signal power supply online monitoring device has a high data acquisition rate, the amount of data that needs to be stored increases accordingly. The use of E2PROM and FLASH cannot meet the requirements, so the use of NVRAM is the best choice. Practice has proved that data redundancy backup when using 32K NVRAM can well ensure data security.