10A supercap back-up chip does everything

Linear Tech has introduced a supercapacitor charger and bi-directional dc-dc converter IC that includes all of the controller features needed for stand-alone capacitor-based power back-up.

Called LTC3350, it operates from 4.5 to 35V input voltage range can both charge and back up at 10A.

Balancing and over-voltage protection is provided for a series stack of one to four supercapacitors, with a synchronous step-down controller driving external n-channel mosfets for constant current constant voltage charging at up to 5V per capacitor.

In back-up mode, the same converter runs in reverse as a synchronous step-up to deliver power from the capacitor stack to the backed-up system.

Ideal diode controllers working with external n-mosfets provide low-loss paths from the input to the backed-up system in normal operation, as well as a second path from the capacitors to the system in back-up mode. The two capacitor to load paths switch-over automatically – see graph.

Glitch ride-through applications are expected in 12V uninterruptible power supplies (UPS) for servers, mass storage and high availability systems. Other apps include data back-up for solid state drives and non-volatile dual in-line memory modules, as well as ‘dying gasp’ power fail indicators – particularly medical and industrial indicators.

An internal 14bit ADC monitors input and output voltage and current.

Within the stack: voltage, capacitance and equivalent series resistance (ESR) are also monitored to ensure adequate energy storage and power delivery. C and ESR Measurement is performed while the backup system is online, once the stack is fully-charged. It discharges the stack by 200mV through a precision current sink to get its results. If input power fails during this test, the test terminates and back-up begins.

“By monitoring the actual capacitance of the 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,” said the firm.

All system parameters and fault status can be monitored via a I2C bus, and alarm levels can be set to alert the system to changes in the measured parameters.

Packaging is 0,75mm high 5x7mm 38pin QFN package

Operation is over -40 to 125°C junction temperature.

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via Yuichun