DC/DC converter IC provides 1A of carry-over, uninterrupted output current

March 11, 2014 // By Graham Prophet
LTC3355 is a complete ride-through DC/DC system IC that features a main buck regulator with a built-in boost converter for temporary backup, or ride-through, of VOUT during a sudden loss of VIN power, from a single supercapacitor energy source.

The device includes all functions necessary to provide seamless charging of a supercapacitor (or other storage element), including the monitoring of VIN, VOUT and VCAP and automatic switchover to backup power. The LTC3355’s nonsynchronous constant frequency current mode monolithic 1A buck switching regulator provides a 2.7V to 5V regulated output voltage from an input supply up to 20V. The device is ideal for ride-through, “dying gasp” or data backup supplies commonly used in power meters, industrial alarms and solid state drives.

The LTC3355 uses a 1A programmable constant-current/constant-voltage (CC/CV) linear charger powered from VOUT to charge a single supercapacitor, electrolytic capacitor or NiMH battery. A thermal regulation loop maximises charge current while limiting the die temperature to 110°C. When the VIN supply drops below the programmable power-fail comparator input (PFI) threshold, the device’s constant frequency non-synchronous current mode 5A boost switching regulator delivers power from the supercapacitor to VOUT. Backup power can be delivered to VOUT with capacitor voltages as low as 0.5V. The device has programmable boost, charger and VIN current limits. Other features include a VIN power fail indicator, VCAP power good indicator, and VOUT power-on reset (POR) output.

The LTC3355 is available in a thermally enhanced 20-lead, low-profile (0.75mm) 4 x 4 mm QFN package. The device operates over a -40°C to 125°C junction temperature range and costs $3.25 for the E grade (1000).

Linear Technology; www.linear.com/product/LTC3355