LTC3355_15 Datasheet, PDF (1/20 Pages) Linear Technology – 20V 1A Buck DC/DC with Integrated SCAP Charger and Backup Regulator

FEATURES
nn _{VIN Voltage Range: 3V to 20V}
nn _{VOUT Voltage Range: 2.7V to 5V}
nn _{1A Current Mode Buck Main Regulator}
nn _{5A Boost Backup Regulator Powered from Single}
Supercapacitor
nn _{Boost Regulator Operates Down to 0.5V for}
Maximum Utilization of Supercapacitor Energy
nn _{Programmable Supercapacitor Charge Current to}
1A with Overvoltage Protection
nn _{Charger Supports Single Cell CC/CV Battery Charging}
nn _{Programmable VIN Current Limit}
nn _{Programmable Boost Current Limit}
nn _{VIN Power Fail Indicator}
nn _{VCAP Power Good Indicator}
nn _{VOUT Power On Reset Output}
nn _{Compact 20-Lead 4mm × 4mm QFN Package}
APPLICATIONS
nn _{Ride-Through “Dying Gasp” Supplies}
nn _{Power Meters/Industrial Alarms/Solid State Drives}
LTC3355
20V 1A Buck DC/DC with
Integrated SCAP Charger
and Backup Regulator
DESCRIPTION
The LTC^®3355 is a complete input power interrupt ride-
through DC/DC system. The part charges a supercapacitor
while delivering load current to V_OUT, and uses energy from
the supercapacitor to provide continuous V_OUT backup
power when V_IN power is lost. The LTC3355 contains a
nonsynchronous constant frequency current mode mono-
lithic 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 V_OUT. When the V_IN supply drops
below the PFI threshold, the devices’s constant frequency
nonsynchronous current mode 5A boost switching
regulator delivers power from the supercapacitor to V_OUT.
A thermal regulation loop maximizes charge current while
limiting the die temperature to 110°C. The IC has boost,
charger and V_IN programmable current limits. The LTC3355
is available in a 20-lead 4mm × 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.
TYPICAL APPLICATION
Supercapacitor Charger and Ride-Through Power Supply
V_IN
12V _10µF
0.091Ω
10µF
2.49M
200k
5 ^VIN
1µF
6 V_INM5
4 ^VINS
1 PFI
SW1 ₇
PFO
BUCK _{VOUT 15}
1A
FB 2
10 PFOB
13 RSTB
9 CPGOOD
8 EN_CHG
3 MODE
INTV_CC
18
LTC3355
BOOST
I_CHG
12
V_{CAP 14}
SW2
16
17
CFB 11
V_CBST 19
I_BSTPK
20
1µF 60.4k 200k
6.8µH
4.7pF 402k
100k
3.3µH
665k
154k
220pF
3355 TA01a
332k
V_OUT
4V
47µF 1A (MAX)
2.4V
SCAP
1F TO 50F
For more information www.linear.com/LTC3355
Backup Operation
14
CAPACITOR = 3F
12
I_VOUT = 0.125A
10
V_IN
8
6
V_OUT
4
V_CAP
2
0
0
5
10
15
20
TIME (SECONDS)
3355 TA01b
3355fb
1