LTC3355 20V 1A Buck DC/DC with Integrated SCAP Charger and Backup Regulator FeaTures DescripTion
The LTC®3355 is a complete input power interrupt ridethrough DC/DC system. The part charges a supercapacitor while delivering load current to VOUT, and uses energy from the supercapacitor to provide continuous VOUT backup power when VIN power is lost. The LTC3355 contains a nonsynchronous constant frequency current mode monolithic 1A buck switching regulator to provide a 2.7V to 5V regulated output voltage from an input supply of up to 20V. A 1A programmable CC/CV linear charger charges the supercapacitor from VOUT. When the VIN supply drops below the PFI threshold, the devices's constant frequency nonsynchronous current mode 5A boost switching regulator delivers power from the supercapacitor to VOUT. A thermal regulation loop maximizes charge current while limiting the die temperature to 110°C. The IC has boost, charger and VIN programmable current limits. The LTC3355 is available in a 20-lead 4mm Ч 4mm QFN surface mount package.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. n n n VIN Voltage Range: 3V to 20V VOUT Voltage Range: 2.7V to 5V 1A Current Mode Buck Main Regulator 5A Boost Backup Regulator Powered from Single Supercapacitor Boost Regulator Operates Down to 0.5V for Maximum Utilization of Supercapacitor Energy Programmable Supercapacitor Charge Current to 1A with Overvoltage Protection Charger Supports Single Cell CC/CV Battery Charging Programmable VIN Current Limit Programmable Boost Current Limit VIN Power Fail Indicator VCAP Power Good Indicator VOUT Power On Reset Output Compact 20-Lead 4mm Ч 4mm QFN Package applicaTions Ride-Through "Dying Gasp" Supplies Power Meters/Industrial Alarms/Solid State Drives Typical applicaTion
Supercapacitor Charger and Ride-Through Power Supply
VIN 12V 0.091 10µF 10µF 1µF 5 VIN SW1 6.8µH 7 VOUT 4V 47µF 1A (MAX) VOLTAGE (V) Backup Operation
14 12 10 8 6 4 2 0 332k 0 5 VCAP VOUT VIN CAPACITOR = 3F IVOUT = 0.125A 6 VINM5 VINS 4 1 PFI PFO BUCK VOUT 1A 15 4.7pF 402k 100k 2.49M 200k 10 PFOB 13 RSTB 9 CPGOOD 8 EN_CHG 3 MODE INTVCC 18 1µF ICHG 12 60.4k BOOST FB 2 VCAP SW2 LTC3355 14 16 17 3.3µH 665k 2.4V SCAP 1F TO 50F CFB 11 IBSTPK 20 200k VCBST 19 154k 220pF
3355 TA01a 10 TIME (SECONDS) 15 20
3355 TA01b 3355fa For more information www.linear.com/LTC3355 1 LTC3355 absoluTe MaxiMuM raTings
(Note 1) pin conFiguraTion
TOP VIEW INTVCC IBSTPK VCBST SW2 SW2 15 VOUT 21 GND 14 VCAP …
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