10-A backup power controller manages supercapacitor stacks

May 19, 2014 // By Graham Prophet
LTC3350 is a supercapacitor charger and backup controller IC that includes all of the features necessary to provide a complete, standalone capacitor-based backup power solution to provide short-term uninterrupted power in the event of a main power failure, for data backup for solid state drives (SSDs) and nonvolatile dual in-line memory modules (NVDIMMs), power fail alarms in medical and industrial applications, as well as a host of other “dying gasp” power fail indicators.

LTC3350 provides all PowerPath control, capacitor stack charging and balancing, and capacitor “health” monitoring to ensure that the backup system is capable of reliable operation. It features a wide 4.5V to 35V input voltage range and over 10A of charge/backup current capability. The device also provides balancing and overvoltage protection for a series stack of one to four supercapacitors. The LTC3350’s synchronous step-down controller drives N-channel MOSFETs for constant current/voltage charging of the capacitor stack at up to 5V per cell. In backup mode, the step-down converter runs in reverse as a synchronous step-up DC/DC to deliver power from the supercapacitor stack to the system supply to be backed up. The LTC3350’s dual ideal-diode controller uses N-channel MOSFETs for low loss power paths from the input and supercapacitors to the backup system supply. The device is suitable for high current 12V ride-through supplies and short-term uninterruptible power supplies (UPS) for servers, mass storage and high availability systems.

The LTC3350 contains an accurate 14-bit analogue-to-digital converter (ADC), which continuously monitors input and output voltage and current. In addition, the internal measurement system monitors parameters associated with the backup capacitors themselves, including capacitor stack voltage, capacitance and stack ESR (equivalent series resistance) to ensure adequate energy storage and power delivery during backup. By monitoring the actual capacitance of the backup supercapacitors, the LTC3350 provides longer capacitor life by enabling the system to set the capacitor voltage to a minimum value while ensuring the required backup energy is maintained. All system parameters and fault status can be monitored via a two-wire I 2C interface, and alarm levels can be set to alert the system to a sudden change in any of these measured parameters.

The LTC3350 is available in a thermally enhanced 38-lead, low-profile (0.75 mm) 5 x 7 mm QFN package. The device operates over a –40°C to 125°C junction temperature range and is costs $5.25 (1000),

Linear Technology; www.linear.com/product/LTC3350