LTC3128
3A Monolithic Buck-Boost
Supercapacitor Charger and
Balancer with Accurate Input Current Limit
FEATURES
n
n
n
DESCRIPTION
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 program-
mable 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 V
OUT
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.
n
n
n
n
n
n
n
n
±2% Accurate Average Input Current Limit
Programmable Up to 3A
Programmable Maximum Capacitor Voltage Limit
Active Charge Balancing for Fast Charging of
Unmatched Capacitors
Charges Single or Stacked Capacitors
V
IN
Range: 1.73V to 5.5V
V
OUT
Range: 1.8V to 5.5V
<2µA Quiescent Current from V
OUT
When Charged
Output Disconnect in Shutdown: <1µA I
Q
Shutdown
Power-Good Comparator
Power Failure Indicator
Thermally Enhanced 20-Lead (4mm
×
5mm
×
0.75mm)
QFN and 24-Lead TSSOP Packages
APPLICATIONS
n
n
n
n
Supercapacitor Based Backup Power
Memory Backup
Servers, RAID, RF Systems
Industrial, Communications, Computing
TYPICAL APPLICATION
Wide V
IN
(3A Programmed Input Current) to 4.2V
3.3µH
SW2
RSENP V
OUTP
RSENS V
OUTS
LTC3128
V
IN
MID
RUN
PFI
FB
PFO
PGOOD
MAXV
PROG
GND
SW1
127k
470pF
3.57k
V
OUT
= 4.2V
1.87M
C1a
940mF
C1b
940mF
V
OUT
2.0V/DIV
C1
MID
2.0V/DIV
I
IN
2.0A/DIV
I
LOAD
2.0A/DIV
2 SECONDS/DIV
3128 TA01b
Stacked Output Capacitors Charging Waveform
1.7V TO 5.5V
UP TO 3.0A
10µF
10µF
301k
3128 TA01
C1: Murata DMF3Z5R5H474M3DTA0
3128f
For more information
www.linear.com/LTC3128
1
LTC3128
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
, RSENP, V
OUTP
, MID Voltage .................. –0.3V to 6V
RSENS, V
OUTS
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
TOP VIEW
SW1
SW2
SW2
NC
SW1
GND
GND
16 V
OUTP
15 V
OUTP
21
GND
14 V
OUTS
13 MID
12 PGOOD
11 FB
7
V
IN
8
PFO
9 10
PFI
MAXV
SW1
RSENP
RSENS
RUN
PROG
NC
1
2
3
4
5
6
7
8
9
25
GND
24 SW2
23 SW2
22 NC
21 V
OUTP
20 V
OUTP
19 V
OUTS
18 MID
17 PGOOD
16 FB
15 MAXV
14 PFI
13
PFO
20 19 18 17
SW1 1
RSENP 2
RSENS 3
RUN 4
PROG 5
NC 6
NC 10
V
IN
11
GND 12
UFD PACKAGE
20-LEAD (4mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB (NOTE 5)
FE PACKAGE
24-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 38°C/W
EXPOSED PAD (PIN 25) SHOULD BE SOLDERED TO PCB (NOTE 5)
ORDER INFORMATION
LEAD FREE FINISH
LTC3128EUFD#PBF
LTC3128IUFD#PBF
LTC3128EFE#PBF
LTC3128IFE#PBF
TAPE AND REEL
LTC3128EUFD#TRPBF
LTC3128IUFD#TRPBF
LTC3128EFE#TRPBF
LTC3128IFE#TRPBF
PART MARKING
3128
3128
LTC3128FE
LTC3128FE
PACKAGE DESCRIPTION
20-Lead (4mm
×
5mm) Plastic QFN
20-Lead (4mm
×
5mm) Plastic QFN
24-Lead Plastic TSSOP
24-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
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/
3128f
2
For more information
www.linear.com/LTC3128
LTC3128
ELECTRICAL CHARACTERISTICS
PARAMETER
Input Operating Range
Programmed Output Voltage Range
FB Voltage
FB Voltage Hysteresis
FB Input Current
Switching Frequency
Power Good Rising Threshold Voltage
Power Good Hysteresis
Power Good Voltage Low
Power Good Leakage Current
PFI Falling Threshold
PFI Hysteresis Current
PFI Input Current
PFO
Voltage Low
PFO
Leakage Current
Maximum Capacitor Voltage – Rising
V
PFI
< 0.565V
V
PFI
> 0.590V
I
PFO
= 5mA
PFO
= 5.5V
R
MAXV
= 125k, –40°C to 125°C (Note 7)
R
MAXV
= 125k, 0°C to 85°C (Notes 6, 7)
R
MAXV
= 113k, –40°C to 125°C (Note 7)
R
MAXV
= 113k, 0°C to 85°C (Notes 6, 7)
l
l
l
l
The
l
denotes specifications that apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. (Note 2) V
IN
= 3.3V, V
OUT
= 4.8V, unless otherwise noted.
CONDITIONS
l
l
l
MIN
1.73
1.8
0.565
TYP
MAX
5.5
5. 5
UNITS
V
V
V
mV
nA
MHz
%FB
%
mV
0.580
8.5
0.5
0.590
2
1.40
99.00
FB > 0.590V
While Charging
Measured as a % of FB Voltage
Measured as a % of FB Voltage
I
PGOOD
= 5mA
PGOOD = 5.5V
l
l
l
1.00
94.50
1.20
96.75
3.6
200
0.1
1
0.590
2
1
2.650
2.600
2.380
2.350
200
µA
V
µA
nA
mV
µA
V
V
V
V
mV
µA
µA
µA
µA
0.565
0.580
0.2
0.5
200
0.1
2.350
2.400
2.150
2.170
2.500
2.500
2.260
2.260
120
20
Maximum Capacitor Voltage Hysteresis
MAXV Pin Current
V
IN
Quiescent Current – Sleep
V
OUT
Quiescent Current – Sleep
V
IN
Quiescent Current – Shutdown
V
OUT
Quiescent Current – Shutdown
V
OUT
Quiescent Current – Shutdown
V
IN
Quiescent Current – Active
V
IN
Quiescent Current – UVLO
V
OUT
Quiescent Current – UVLO
Input Current Limit
V
RUN
= 3.3V, V
FB
> 0.590V
V
RUN
= 3.3V, Not Balancing, V
FB
> 0.590V
V
RUN
= 3.3V, Balancing, V
FB
> 0.590V
V
RUN
= 0V, Not Including SW Leakage
V
RUN
= 0V, Not Including SW Leakage
V
RUN
= 0V, V
IN
= 0V, Not Including SW Leakage
V
RUN
= 3.3V (Note 3)
V
RUN
= 1.5V, V
IN
= 1.5V, Not Including SW Leakage
V
RUN
= 1.5V, V
IN
= 1.5V, Not Including SW Leakage
R
PROG
= 22.1k (Notes 3, 7)
R
PROG
= 22.1k (Notes 3, 7)
R
PROG
= 11k (Notes 3, 7)
R
PROG
= 11k (Notes 3, 7)
R
PROG
= 5.49k (Notes 3, 7)
R
PROG
= 5.49k (Notes 3, 7)
R
PROG
= 3.57k (Notes 3, 7)
R
PROG
= 3.57k (Notes 3, 7)
l
l
l
l
14
1.9
100
0.6
0.4
0.4
600
25
1
489
475
985
958
1973
1923
3034
2951
497
497
1000
1000
2003
2003
3081
3081
2
504
515
1015
1035
2033
2075
3127
3185
1
1
1
µA
µA
µA
µA
µA
µA
mA
mA
mA
mA
mA
mA
mA
mA
3128f
For more information
www.linear.com/LTC3128
3
LTC3128
The
l
denotes specifications that apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. (Note 2) V
IN
= 3.3V, V
OUT
= 4.8V, unless otherwise noted.
PARAMETER
PROG Pin Gain
Internal Sense Resistor Value
Peak Inductor Current Limit
Linear Inductor Current Limit
N-Channel MOSFET Leakage
P-Channel MOSFET Leakage
N-Channel MOSFET On-Resistance
CONDITIONS
Measured at I
IN
= 1A (Note 3)
(Note 6)
(Note 3)
(Note 3)
Switches B and C and E
Switches A and D
Switch F
Switch B
Switch C
Switch E (V
OUT
= 0V)
Switch A
Switch D
Switch F
V
MID
= 0V, V
IN
= 3.3V, V
SW1
= 3.3V
V
OUT
= 4.8V
|V
OUT
/2-V
MID
|
(Note 3)
(Note 3)
l
l
l
l
l
ELECTRICAL CHARACTERISTICS
MIN
TYP
52.7
50
MAX
UNITS
µA/A
mΩ
5.50
4.00
6.5
5.0
0.1
0.1
0.1
70
80
95
45
40
300
0.1
9.00
6.85
5
5
10
A
A
µA
µA
µA
mΩ
mΩ
mΩ
mΩ
mΩ
mΩ
P-Channel MOSFET On-Resistance
MID Leakage Current
MID Pin Regulation
Active Charge Balancer Enable Threshold
Active Charge Balancer Hysteresis
Active Charge Balancer Peak Current
Active Charge Balancer Valley Current
RUN Input High Threshold Voltage
RUN Input Low Threshold Voltage
RUN Input Current
10
2.496
118
µA
V
mV
mV
mA
mA
V
2.304
2.400
60
60
400
50
1.2
0.3
0.01
1
V
µA
RUN = 5.5V
Note 1.
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2.
The LTC3128 is tested under pulsed load conditions such that T
J
≈
T
A
. The LTC3128E is guaranteed to meet specifications from 0°C to 85°C
junction temperature. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3128I is guaranteed
over the full –40°C to 125°C operating junction temperature range.
The junction temperature (T
J
) is calculated from the ambient temperature
(T
A
) and power dissipation (P
D
) according to the formula: T
J
= T
A
+ (P
D
•
θ
JA
°C/W), where
θ
JA
is the package thermal impedance. Note that the
maximum ambient temperature consistent with these specifications is
determined by specific operating conditions in conjunction with board
layout, the rated package thermal resistance and other environmental
factors.
Note 3.
Current measurements are made when the output is not switching.
Note 4.
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may result in device degradation or failure.
Note 5.
Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
43°C/W in the QFN and 38°C/W in the TSSOP
.
Note 6.
Guaranteed by design. Not tested.
Note 7.
Accuracy of this specification is directly related to the accuracy of
the resistor used to program the parameter.
3128f
4
For more information
www.linear.com/LTC3128
LTC3128
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs V
OUT
(0.5A I
IN
)
100
90
EFFICIENCY (%)
EFFICIENCY (%)
80
70
60
50
40
0.5
100
90
80
70
60
50
40
5
5.5
30
0.5
1
1.5
2
V
IN
= 1.7V
V
IN
= 2.4V
V
IN
= 3.3V
V
IN
= 4.2V
V
IN
= 5.0V
2.5 3 3.5
V
OUT
(V)
4
4.5
5
5.5
T
A
= 25°C, unless otherwise noted.
Efficiency vs V
OUT
(1.0A I
IN
)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
Efficiency vs V
OUT
(2.0A I
IN
)
V
IN
= 1.7V
V
IN
= 2.4V
V
IN
= 3.3V
V
IN
= 4.2V
V
IN
= 5.0V
1
1.5
2
2.5 3 3.5
V
OUT
(V)
4
4.5
0
0.5
V
IN
= 2.4V
V
IN
= 3.3V
V
IN
= 4.2V
V
IN
= 5.0V
1
1.5
2
2.5 3 3.5
V
OUT
(V)
4
4.5
5
5.5
3128 G01
3128 G02
3128 G03
Efficiency vs V
OUT
(3.0A I
IN
)
NORMALIZED AVERAGE INPUT CURRENT (%)
90
80
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0.5
1
1.5
2
2.5 3 3.5
V
OUT
(V)
4
V
IN
= 2.4V
V
IN
= 3.3V
V
IN
= 4.2V
V
IN
= 5.0V
4.5
5
5.5
1.0
0.5
0
Average Input Current Limit
vs Temperature (Normalized)
5.5
5.0
4.5
4.0
V
OUT
(V)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
–2.0
–45
–25 –5
15 35 55 75
TEMPERATURE (°C)
95 115
3128 G05
V
OUT
vs Charge Time, C
OUT
= 1F
,
R
ESR
= 20mΩ, I
IN
= 0.5A
–0.5
–1.0
–1.5
0
V
IN
= 1.7V
V
IN
= 2.4V
V
IN
= 3.3V
V
IN
= 4.2V
V
IN
= 5.0V
0
2
4
6
8 10 12 14 16 18 20 22 24
TIME (s)
3128 G21
3128 G04
V
OUT
vs Charge Time, C
OUT
= 1F
,
R
ESR
= 20mΩ, I
IN
= 1.0A
5.5
5.0
4.5
4.0
V
OUT
(V)
V
OUT
(V)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
IN
= 1.7V
V
IN
= 2.4V
V
IN
= 3.3V
V
IN
= 4.2V
V
IN
= 5.0V
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
TIME (s)
3128 G22
V
OUT
vs Charge Time, C
OUT
= 1F
,
R
ESR
= 20mΩ, I
IN
= 2.0A
5.5
5.0
4.5
4.0
3.0
2.5
2.0
1.5
1.0
0.5
0
V
IN
= 2.4V
V
IN
= 3.3V
V
IN
= 4.2V
V
IN
= 5.0V
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
TIME (s)
3128 G23
V
OUT
vs Charge Time, C
OUT
= 1F
,
R
ESR
= 20mΩ, I
IN
= 3.0A
5.5
5.0
4.5
4.0
V
OUT
(V)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
IN
= 2.4V
V
IN
= 3.3V
V
IN
= 4.2V
V
IN
= 5.0V
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
TIME (s)
3128 G24
3.5
3128f
For more information
www.linear.com/LTC3128
5
京公网安备 11010802033920号
EEWORLD
