Document
LTC3128 3A Monolithic Buck-Boost Supercapacitor Charger and Balancer with Accurate Input Current Limit
FEATURES
DESCRIPTION
n ±2% Accurate Average Input Current Limit Programmable Up to 3A
n Programmable Maximum Capacitor Voltage Limit n Active Charge Balancing for Fast Charging of
Unmatched Capacitors n Charges Single or Stacked Capacitors n VIN Range: 1.73V to 5.5V n VOUT Range: 1.8V to 5.5V n <2µA Quiescent Current from VOUT When Charged n Output Disconnect in Shutdown: <1µA IQ Shutdown n Power-Good Comparator n Power Failure Indicator n Thermally Enhanced 20-Lead (4mm × 5mm × 0.75mm)
QFN and 24-Lead TSSOP Packages
APPLICATIONS
n Supercapacitor Based Backup Power n Memory Backup n Servers, RAID, RF Systems n Industrial, Communications, Computing
The LTC®3128 is a highly efficient, buck-boost DC/DC supercapacitor charger. It operates efficiently from input voltages above, below or equal to the output voltage. The LTC3128 incorporates accurate programmable average input current limit, active charge balancing and programmable maximum capacitor voltage. This combination of features makes the LTC3128 ideal for safely charging and protecting large capacitors in backup power systems. The input current limit and maximum capacitor voltage are each programmed using a single resistor. Average input current is accurately controlled over a 0.5A to 3A programmable range while the individual maximum capacitor voltage can be set from 1.8V to 3.0V. Other features of the LTC3128 include <2µA quiescent current from VOUT in Burst Mode®operation, accurate power-good and power failure indicators, and thermal overload protection. The LTC3128 is offered in low profile, thermally enhanced 20-Lead 4mm × 5mm × 0.75mm QFN and 24-Lead TSSOP packages.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Wide VIN (3A Programmed Input Current) to 4.2V
3.3µH
1.7V TO 5.5V UP TO 3.0A
10µF
10µF
SW1 SW2
RSENP RSENS
VVOOUUTTPS
RVIUNNLTC3128MID
PFI PFO
FB
PGOOD MAXV PROG
GND
127k
VOUT = 4.2V 1.87M
C1a 940mF
C1 C1b 940mF
470pF 3.57k 301k
3128 TA01
C1: Murata DMF3Z5R5H474M3DTA0
Stacked Output Capacitors Charging Waveform
VOUT 2.0V/DIV
MID 2.0V/DIV
IIN 2.0A/DIV
ILOAD 2.0A/DIV
2 SECONDS/DIV
3128 TA01b
For more information www.linear.com/LTC3128
3128f
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LTC3128
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN, RSENP, VOUTP, MID Voltage................... –0.3V to 6V RSENS, VOUTS Voltage.................................. –0.3V to 6V RSENS DC Current.....................................................–4A SW1, SW2 DC Voltage.................................. –0.3V to 6V SW1, SW2 Pulsed (<100ns) Voltage..............–1.0V to 7V PGOOD, PFO, RUN Voltage........................... –0.3V to 6V
PROG, MAXV, FB, PFI Voltage...................... –0.3V to 6V PGOOD, PFO DC Current.........................................15mA Operating Junction Temperature Range (Notes 2, 4)............................................. –40°C to 125°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) FE Only.............................................................. 300°C
PIN CONFIGURATION
TOP VIEW
VIN NC PFO SW1 PFI SW2 MAXV SW2
SW1 1 RSENP 2 RSENS 3
RUN 4 PROG 5
NC 6
20 19 18 17
16 VOUTP 15 VOUTP 21 14 VOUTS GND 13 MID 12 PGOOD 11 FB
7 8 9 10
UFD PACKAGE 20-LEAD (4mm × 5mm) PLASTIC QFN
TJMAX = 125°C, θJA = 43°C/W EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB (NOTE 5)
SW1 1 GND 2 GND 3 SW1 4 RSENP 5 RSENS 6 RUN 7 PROG 8
NC 9 NC 10 VIN 11 GND 12
TOP VIEW 25 GND
24 SW2 23 SW2 22 NC 21 VOUTP 20 VOUTP 19 VOUTS 18 MID 17 PGOOD 16 FB 15 MAXV 14 PFI 13 PFO
FE PACKAGE 24-LEAD PLASTIC TSSOP TJMAX = 125°C, θJA = 38°C/W EXPOSED PAD (PIN 25) SHOULD BE SOLDERED TO PCB (NOTE 5)
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
LTC3128EUFD#PBF
LTC3128EUFD#TRPBF 3128
20-Lead (4mm × 5mm) Plastic QFN
LTC3128IUFD#PBF
LTC3128IUFD#TRPBF 3128
20-Lead (4mm × 5mm) Plastic QFN
LTC3128EFE#PBF
LTC3128EFE#TRPBF
LTC3128FE
24-Lead Plastic TSSOP
LTC3128IFE#PBF
LTC3128IFE#TRPBF
LTC3128FE
24-Lead Plastic TSSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
TEMPERATURE RANGE –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C
3128f
2 For more information www.linear.com/LTC3128
LTC3128
E LECTRICAL CHARACTERISTICS The l denotes specifications that apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C. (Note 2) VIN = 3.3V,.