LTC3355
20V 1A Buck DC/DC with
Integrated SCAP Charger
and Backup Regulator
FEATURES DESCRIPTION
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V Voltage Range: 3V to 20V The LTC 3355 is a complete input power interrupt ride-
IN
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V Voltage Range: 2.7V to 5V through DC/DC system. The part charges a supercapacitor
OUT
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1A Current Mode Buck Main Regulator while delivering load current to V , and uses energy from
OUT
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5A Boost Backup Regulator Powered from Single the supercapacitor to provide continuous V backup
OUT
Supercapacitor power when V power is lost. The LTC3355 contains a
IN
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Boost Regulator Operates Down to 0.5V for nonsynchronous constant frequency current mode mono-
Maximum Utilization of Supercapacitor Energy lithic 1A buck switching regulator to provide a 2.7V to 5V
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Programmable Supercapacitor Charge Current to regulated output voltage from an input supply of up to 20V.
1A with Overvoltage Protection
A 1A programmable CC/CV linear charger charges the
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Charger Supports Single Cell CC/CV Battery Charging
supercapacitor from V . When the V supply drops
OUT IN
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Programmable V Current Limit
IN
below the PFI threshold, the devicess constant frequency
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Programmable Boost Current Limit
nonsynchronous current mode 5A boost switching
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V Power Fail Indicator
IN
regulator delivers power from the supercapacitor to V .
OUT
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V Power Good Indicator
CAP
A thermal regulation loop maximizes charge current while
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V Power On Reset Output
OUT
limiting the die temperature to 110C. The IC has boost,
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Compact 20-Lead 4mm 4mm QFN Package
charger and V programmable current limits. The LTC3355
IN
is available in a 20-lead 4mm 4mm QFN surface mount
APPLICATIONS
package.
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Ride-Through Dying Gasp Supplies
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
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Power Meters/Industrial Alarms/Solid State Drives
owners.
TYPICAL APPLICATION
Supercapacitor Charger and Ride-Through Power Supply
Backup Operation
6.8H
0.091 V
IN SW1
V
IN
14
5 7
12V
CAPACITOR = 3F
10F 10F 1F
I = 0.125A
VOUT
V
6 12
INM5
PFO BUCK V
OUT
V
V OUT
INS
4V
15
4
10
47F 1A (MAX)
4.7pF
402k
2.49M
1A V
IN
FB 2
PFI 8
1
100k
200k
LTC3355
6
V
CAP
10 PFOB
14 V
OUT
3.3H
SW2 4
13 RSTB
16 2.4V
V
CAP
SCAP
CPGOOD
9 BOOST 2
17
665k 1F TO 50F
8
EN_CHG
CFB
11
0
0 5 10 15 20
3 MODE
332k
V 19
CBST
INTV I TIME (SECONDS)
I
CC CHG BSTPK
154k
3355 TA01b
18 12
20
220pF
1F 60.4k 200k
3355 TA01a
3355fb
1
For more information www.linear.com/LTC3355
VOLTAGE (V)LTC3355
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Note 1)
TOP VIEW
V , V , V ........................................................22V
IN INS INM5
V V .................................................................. 0.1V
IN INS
V .......................................................... 0.4V to 22V
SW1
20 19 18 17 16
V ............................................................ 0.4V to 6V
SW2
PFI V
1 15
V , INTV , PFOB, RSTB, OUT
OUT CC
FB 2 14 V
CAP
CPGOOD, V ............................................. 0.3V to 6V
CAP
21
MODE 3 13 RSTB
GND
PFI, EN_CHG, MODE, FB .............................. 0.3V to 6V
V 4 12 I
INS CHG
CFB ............................................0.3V to INTV + 0.3V
CC
V 11 CFB
5
IN
I , I , I ................................................1mA
CPGOOD PFOB RSTB
6 7 8 9 10
Operating Junction Temperature Range
(Notes 2, 3) ............................................ 40C to 125C
Storage Temperature Range .................. 65C to 150C
UF PACKAGE
20-LEAD (4mm 4mm) PLASTIC QFN
T = 125C, = 47C/W
JMAX JA
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3355EUF#PBF LTC3355EUF#TRPBF 3355 20-Lead (4mm 4mm) Plastic QFN 40C to 125C
LTC3355IUF#PBF LTC3355IUF#TRPBF 3355 20-Lead (4mm 4mm) Plastic QFN 40C to 125C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to: