LTC3643
2A Bidirectional
Power Backup Supply
FEATURES DESCRIPTION
n
Bidirectional Synchronous Boost Capacitor The LTC 3643 is a bidirectional synchronous step-
Charger/Buck Regulator for System Backup up charger and step-down converter which efficiently
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Wide Input Voltage Range: 3V to 17V charges a capacitor array up to 40V from an input supply
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Up to 40V Capacitor Voltage Storage for High between 3V to 17V. When the input supply falls below the
Energy Backup programmable power-fail threshold, the step-up charger
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2A Maximum CAP Charge Current operates in reverse as a synchronous step-down regulator
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Integrated Power N-Channel MOSFETs to power the system rail from the backup capacitor during
(150m Top and 75m Bottom) this power interruption/failure condition.
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Integrated Power N-Channel MOSFET for Output/CAP
When charging the backup capacitor, an external low-
Disconnect (50m)
value sense resistor may be used to maintain an accu-
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Input Current Limit During Charging
rate current limit from the input supply or implement
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Fast 1MHz Switching Frequency
PowerPath functionality.
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1% Reference Accuracy for System Voltage Regulation
n The step-down converter operates at a 1MHz switching
Indicator Outputs for Charge Status and Input Power Fail
n frequency, allowing small external components to be
Low Profile 24-lead 3mm 5mm QFN Package
used. Low quiescent current during regulation maximizes
the energy usage from the backup capacitor.
APPLICATIONS
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and PowerPath is trademarks of Analog Devices, Inc. All other trademarks are the property of
n
Backup Capacitor Systems
their respective owners. Protected by U.S. Patents. Including 5481178, 6580258, 6498466,
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6611131, 5705919.
Power Failure Backup Systems
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Solid-State Drives
TYPICAL APPLICATION
Approximate Charge/Backup Time per
40V Backup System Regulating System Supply to 5V
1mF of Storage Cap (40V Backup)
500
0.01
POWER
CHARGE TIME
SUPPLY
0.1F BACKUP TIME WITH 2A LOAD
4.7H 47F
BACKUP TIME WITH 1A LOAD
SYSTEM LOAD
400
BACKUP TIME WITH 0.5A LOAD
CLP V INDIS SW BOOST
IN
40V BACKUP 300
GATE
CAP
+
22F
INTV
35.7k CC
RUN
1mF
4.7F 200
PFI
392k
LTC3643 ENERGY
44.2k
FBCAP
100
STORAGE
FBSYS
6.04k
12.1k 6.04k
ITH
0
CAPGD
3 6 9 12 15
400k
22pF
PFO
SYSTEM LOAD VOLTAGE (V)
GND
470pF 3643 TA01b
3643 TA01a
3643fc
1
For more information www.linear.com/LTC3643
CHARGE/BACKUP TIME (ms)LTC3643
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Note 1)
V ............................................................. 0.3V to 17V
IN
TOP VIEW
RUN .................................................. 0.3V to V +0.3V
IN
CLP ............................................................ 0.3V to 17V
CAP ............................................................ 0.3V to 42V
24 23 22 21
BOOST-SW ................................................... 0.3V to 4V
PGND 1 20 SW
PGND 2 SW
INTV , FBSYS, FBCAP ................................ 0.3V to 4V 19
CC
CAP 3 18 SW
PFI ............................................................... 0.3V to 4V
V 4 17 INDIS
IN
25
I .............................................0.3V to V +0.3V
LIM INTVCC
SGND
V 5 16 INDIS
IN
PFO, CAPGD ................................................ 0.3V to 6V
GATE 6 15 BOOST
Operating Junction Temperature Range
RUN 7 INTV
14
CC
(Note 2) ............................................. 40C to 125C
FBSYS 8 13 PFI
Storage Temperature Range .................. 65C to 150C
9 10 11 12
Lead Temperature (Soldering, 10sec).................... 260C
UDD PACKAGE
24-LEAD (3mm 5mm) PLASTIC QFN
T = 125C, = 46C/W, = 5.0C/W
JMAX JA JC
EXPOSED PAD (PIN 25) IS SGND, MUST BE SOLDERED TO PCB