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PDF LTC3625 Data sheet ( Hoja de datos )
| Número de pieza | LTC3625 | |
| Descripción | 1A High Efficiency 2-Cell Supercapacitor Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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DataSheet.in
Features
n High Efficiency Step-Up/Step-Down Charging of Two
Series Supercapacitors
n Automatic Cell Balancing Prevents Capacitor
Overvoltage During Charging
n Programmable Charging Current Up to 500mA
(Single Inductor), 1A (Dual Inductor)
n VIN = 2.7V to 5.5V
n Selectable 2.4V/2.65V Regulation per Cell (LTC3625)
n Selectable 2V/2.25V Regulation per Cell (LTC3625-1)
n Low No-Load Quiescent Current: 23µA
n IVOUT, IVIN < 1µA in Shutdown
n Low Profile 12-lead 3mm × 4mm DFN Package
Applications
n Servers, RAID Systems, Mass Storage, High Current
Backup Supplies
n Solid State Hard Drives
n Wireless Power Meters
n High Peak Power Boosted Supplies
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
LTC3625/LTC3625-1
1A High Efficiency 2-Cell
Supercapacitor Charger
with Automatic Cell
Balancing
Description
The LTC®3625/LTC3625-1 are programmable supercapaci-
tor chargers designed to charge two supercapacitors in
series to a fixed output voltage (4.8V/5.3V or 4V/4.5V
selectable) from a 2.7V to 5.5V input supply. Automatic
cell balancing prevents overvoltage damage to either
supercapacitor while maximizing charge rate. No balancing
resistors are required.
High efficiency, high charging current, low quiescent cur-
rent and low minimum external parts count (one inductor,
one bypass capacitor at VIN and one programming resistor)
make the LTC3625/LTC3625-1 ideally suited for small form
factor backup or high peak power systems.
Charging current/maximum input current level is pro-
grammed with an external resistor. When the input supply is
removed and/or the EN pin is low, the LTC3625/LTC3625-1
automatically enter a low current state, drawing less than
1µA from the supercapacitors.
The LTC3625/LTC3625-1 are available in a compact
12‑lead 3mm × 4mm × 0.75mm DFN package.
Typical Application
1A SCAP Charger
VIN
2.7V TO 5.5V
VIN
10µF
LTC3625
61.9k
PROG
VOUT
SW2
SW1
VMID
3.3µH
3.3µH
PFI
EN
CTL
VSEL
PGOOD
PFO
3625 TA01a
VOUT
4.8V
CTOP ≥ 0.1F
CBOT ≥ 0.1F
Charging Two 2:1 Mismatched Supercapacitors
6
CTOP = 50F
5
CBOT = 100F
RPROG = 61.9k
CTL = 0
4 VSEL = 0
VOUT
3
2
VMID
1
0
0 20 40 60 80 100 120 140 160 180 200
TIME (SECONDS)
3625 TA01b
3625f
1 page  
DataSheet.in
LTC3625/LTC3625-1
Typical Performance Characteristics
TA = 25°C, L1 = 3.3µH, L2 = 3.3µH, CIN = 10µF, CTOP = CBOT , LTC3625 unless otherwise specified.
Buck Input Power vs RPROG
8
7
IPROG
CLAMPED
VIN = 5.5V
VMID = 2.65V
CTL = 0V
6 VSEL = VIN
5
4
3
2
1
0
0 50 100 150 200 250 300 350 400 450 500
RPROG (kΩ)
3625 G05
Buck Efficiency vs VMID
100
VIN = 5.5V
90
VSEL = VIN
CTL = 0
80
RPROG = 71.5k
70 RPROG = 143k
RPROG = 286k
60
50
40
0.2 0.6 1.0 1.4 1.8
VMID (V)
2.2 2.6
3625 G08
Boost Efficiency vs VTOP
90
80 NORMAL OPERATION
70
60 VOUT TRICKLE
50 CHARGE OPERATION
40
30
20
–1.5 –1.0 –0.5
VIN = 3.6V
VMID = 2.5V
VTOP = VOUT – VMID
CTL = 0
0 0.5 1.0 1.5 2.0 2.5
VTOP (V)
3625 G11
Buck Efficiency vs IBUCK
100
95
90
85
80
75
70
65
60 VIN = 3.6V
55
VMID = 2V
CTL = 0V
50
200 700
1200 1700
IBUCK (mA)
2200
3625 G06
Buck Output Current vs VMID
2500
2250
2000
RPROG = 71.5k
1750
1500
1250
1000
RPROG = 143k
750 RPROG = 286k
500 VIN = 5.5V
250 VSEL = VIN
0 CTL = 0
0.2 0.6 1.0 1.4 1.8 2.2 2.6
VMID (V)
3625 G09
RFET vs Temperature
0.20
0.25
0.15
PMOS
0.10
0.20
0.15
NMOS
0.05
0.10
0
–40 –25 –10 5
VIN = 2.7V
VIN = 5.5V
0.05
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
3625 G12
Buck Input Power vs VMID
6
VIN = 5.5V
5
VSEL = VIN
CTL = 0
4
RPROG = 71.5k
3
RPROG = 143k
2
RPROG = 286k
1
0
0.2 0.6 1.0 1.4 1.8
VMID (V)
2.2 2.6
3625 G07
Boost Input Current vs VTOP
2500
2000
1500
NORMAL OPERATION
1000
500
VOUT
TRICKLE
CHARGE
OPERATION
0
–1.5 –1.0 –0.5
VIN = 3.6V
VMID = 2.5V
VTOP = VOUT – VMID
CTL = 0
0 0.5 1.0 1.5 2.0 2.5
VTOP (V)
3625 G10
Charge Time vs RPROG
400
VIN = 3.6V
350 VSEL = 3.6V
VOUT INITIAL = 0V
300 CTOP = CBOT = 10F
250
SINGLE
200 INDUCTOR
APPLICATION
150
100 IPROG
50 CLAMPED
DUAL
INDUCTOR
APPLICATION
0
0 50 100 150 200 250 300 350 400 450 500
RPROG (kΩ)
3625 G15
3625f
5 Page 
DataSheet.in
LTC3625/LTC3625-1
Applications Information
Programming Charge Current/Maximum Input Current
The CBOT charge current is programmed with a single
resistor connecting the PROG pin to ground. The program
resistor and buck output current are calculated using the
following equation:
RPROG
=
hPROG
•
1.2V
IBUCK
where hPROG = 118,000 (typical). Excluding quiescent cur-
rent, IBUCK is always greater than the average buck input
current. An RPROG resistor value of less than 53.6k will
cause the LTC3625/LTC3625-1 to enter overcurrent protec-
tion mode and proceed to charge at 2.65A (typical).
The effective buck input current can be calculated as:
IVIN
=
IBUCK
εBUCK
•
VMID
VIN
where eBUCK is the buck converter efficiency (see the
Typical Performance Characteristics graph Buck Efficiency
vs VMID).
Output Voltage Programming
The LTC3625/LTC3625-1 have a VSEL input pin that
allows the user to set the output threshold voltage to
either 4.8V/4.0V or 5.3V/4.5V by forcing a low or high at
the VSEL pin respectively. In the single inductor application
the chip will balance the supercapacitors to within 50mV
(typical) of each other, resulting in a possible 25mV of
over/undercharge per cell. In the dual inductor application
the chip will balance the supercapacitors to within 100mV
(typical) of each other, resulting in a possible 50mV of
over/undercharge per cell.
Thermal Management
If the junction temperature increases above approximately
150°C, the thermal shutdown circuitry automatically de-
activates the output. To reduce the maximum junction
temperature, a good thermal connection to the PC board
is recommended. Connecting the exposed pad (Pin 13) of
the DFN package to a ground plane under the device on two
layers of the PC board, will reduce the thermal resistance
of the package and PC board considerably.
VIN Capacitor Selection
The style and value of capacitors used with the LTC3625/
LTC3625-1 determine input voltage ripple. Because the
LTC3625/LTC3625-1 use a step-down switching power sup-
ply from VIN to VMID, its input current waveform contains
high frequency components. It is strongly recommended
that a low equivalent series resistance (ESR) multilayer
ceramic capacitor be used to bypass VIN.
Tantalum and aluminum capacitors are not recommended
because of their high ESR. The value of the capacitor on
VIN directly controls the amount of input ripple for a given
IBUCK. Increasing the size of this capacitor will reduce the
input ripple.
Multilayer ceramic chip capacitors typically have excep-
tional ESR performance. MLCCs combined with a tight
board layout and an unbroken ground plane will yield
very good performance and low EMI emissions. There are
several types of ceramic capacitors available, each having
considerably different characteristics. For example, X7R
ceramic capacitors have the best voltage and temperature
stability. X5R ceramic capacitors have higher packing
density but poorer performance over their rated voltage
and temperature ranges. Y5V ceramic capacitors have
the highest packing density, but must be used with cau-
tion because of their extreme non-linear characteristic of
capacitance verse voltage.
The actual in-circuit capacitance of a ceramic capacitor
should be measured with a small AC signal as is expected
in-circuit. Many vendors specify the capacitance versus
voltage with a 1VRMS AC test signal and as a result,
overstate the capacitance that the capacitor will present
in the application. Using similar operating conditions as
the application, the user must measure or request from
the vendor the actual capacitance to determine if the
selected capacitor meets the minimum capacitance that
the application requires.
Inductor Selection
Many different sizes and shapes of inductors are avail-
able from numerous manufacturers. Choosing the right
inductor from such a large selection of devices can be
overwhelming, but following a few basic guidelines will
make the selection process much simpler.
3625f
11
11 Page | ||
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| PDF Descargar | [ Datasheet LTC3625.PDF ] | |
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