Entering the 21st century, the majority of people around the world handle many daily tasks using PCs in their hands, going beyond personal computers. This series of activities is made possible by the real-time processing of vast amounts of data in Internet Data Centers (IDCs), which are buildings of massive servers invisible to the general public. In other words, this means that if the servers in an IDC were to shut down even for a brief moment, an unimaginable amount of data could vanish into thin air.

Generally, data that enters a server through a network stays in memory for a short time for processing. Once the time spent waiting in memory for processing has passed and the data is safely transmitted to someone's terminal via an HDD or another server, the data processing is considered complete.

However, what happens if the power is cut off due to a malfunction caused by a sudden power outage or a PC overload? Only the data remaining in the volatile memory is immediately blown away.

In the case of personal computers, there would likely be no major problem. However, for medical or defense servers, as well as for the securities industry or banks, such an incident would entail enormous consequences. In the case of banks, customer deposit data via internet banking, and in medical facilities, the pulse rates of emergency patients, could vanish into thin air.

Hong Sa-kwak, president of the Korean branch of LTC, a global company in the analog market, said that one only needs to hold out for two minutes to resolve these difficulties. It is only 2 minutes.

According to the requirements in feedback received from Linear Technology's clients, the time required for all data from memory to be transferred to the hard disk is just over 2 minutes, and if this 2 minutes can be endured, most of the data can be safely saved to the HDD when the server is powered on after shutdown.

To this end, LTC placed the solution in batteries using supercapacitors and developed and announced a high-current supercapacitor backup controller and a battery monitoring system.

Regarding the background of LTC's interest in supercapacitors, Director Noil of LTC explained, "Supercapacitors are a highly suitable application for server systems because they do not cause a trade-off between battery safety and lifespan, and possess excellent power density suitable for instantaneous high-current backup." However, he noted that capacitor condition monitoring is necessary because issues such as capacitor loss and increased ESR occur at high operating temperatures.

The newly announced LTC3350 is an IC designed for short-term uninterruptible power supply to handle major power failures, and it can currently be used in data backup, medical, and industrial applications as a power failure alarm and other “dying gas” power failure indicator.

The LTC3350 provides a wide input voltage range of 4.5V to 35V and charge/backup current performance of over 10A. This device also provides balancing and overvoltage protection by connecting 1 to 4 supercapacitors in series. The LTC3350's synchronous step-down controller drives N-channel MOSFETs for constant current/voltage charging of capacitor stacks at up to 5V per cell. In backup mode, the step-down converter operates in reverse as a synchronous step-up DC/DC converter, allowing power to be supplied from the supercapacitor stack to the system power supply for backup. The LTC3350's dual ideal diode controller utilizes N-channel MOSFETs for low-loss power paths from the input and supercapacitors to the backup system. This device is ideal for high-current 12V ride-through power supplies, as well as short-term uninterruptible power supplies (UPS) for servers, mass storage, and high availability systems.

The LTC3350 includes a precise 14-bit analog-to-digital converter (ADC) that continuously monitors input and output voltages and currents. Additionally, an internal measurement system monitors parameters related to backup capacitors, including capacitor stack voltage, capacitance, and stack ESR (equivalent series resistance), to ensure sufficient energy storage and power supply during backup. By monitoring the actual capacitance of the backup supercapacitors, the LTC3350 extends the lifespan of the capacitors by allowing the system to maintain essential backup energy while setting the capacitor voltage to a minimum value. All system parameters and error statuses can be monitored via two wired I2C interfaces, and alarm levels can be set to notify the system of sudden changes in the measured parameters.

The LTC3350 is available in a thermally enhanced 38-pin low-profile (0.75mm) 5mm x 7mm QFN package.

Product Features: LTC3350
• High-efficiency synchronous step-down CC/CV charging 1 to 4 series supercapacitors
• Step-up mode during backup allows for better utilization of energy stored in the supercapacitor.
• 14-bit ADC monitoring system voltage/current, capacitance & ESR
• Active overvoltage protection shunt
• Internal active balancer – No balancer resistor required
• VIN: 4.5V ~ 35V, VCAP(n): Max. 5V per capacitor, Charge/Backup Current: 10A+
• Programmable input current limit prioritizes system load in capacitor charging current.
• Dual Ideal Diode PowerPath™ Controller
• All N-FET Charger Controllers & PowerPath Controllers
• Compact 38-pin 5mm × 7mm QFN package

Text and photos by Myung Se-hwan