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PDF LTC4040 Data sheet ( Hoja de datos )
| Número de pieza | LTC4040 | |
| Descripción | 2.5A Battery Backup Power Manager | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC4040
2.5A Battery Backup
Power Manager
Features
Description
nn Step-Up Backup Supply and Step-Down Battery
Charger
nn 6.5A Switches for 2.5A Backup from 3.2V Battery
nn Input Current Limit Prioritizes Load Over Charge
Current
nn Input Disconnect Switch Isolates Input During Backup
nn Automatic Seamless Switch-Over to Backup Mode
nn Input Power Loss Indicator
nn System Power Loss Indicator
nn Pin Selectable Battery: Li-Ion (3.95V/4.0V/4.05V/4.1V)
or LiFePO4 (3.45V/3.5V/3.55V/3.6V)
nn Optional OVP Circuitry Protects Device to >60V
nn Constant Frequency Operation
nn Low Profile (0.75mm) 24-Lead 4mm × 5mm QFN Package
Applications
nn Fleet and Asset Tracking
nn Automotive GPS Data Loggers
nn Automotive Telematics Systems
nn Toll Collection Systems
nn Security Systems
nn USB Powered Devices
The LTC®4040 is a complete 3.5V to 5.5V supply rail battery
backup system. It contains a high current step-up DC/DC
regulator to back up the supply from a single-cell Li-Ion
or LiFePO4 battery. When external power is available,
the step-up regulator operates in reverse as a step-down
battery charger.
The LTC4040’s adjustable input current limit function
reduces charge current to protect the main supply from
overload while an external disconnect switch isolates the
external supply during backup. When the input supply
drops below the adjustable PFI threshold, the 2.5A boost
regulator delivers power from the battery to the system
output.
An optional input overvoltage protection (OVP) circuit
protects the LTC4040 from high voltage damage at the
VIN pin. One logic input selects either the Li-Ion or the
LiFePO4 battery option, and two other logic inputs program
the battery charge voltage to one of four levels suitable
for backup applications. The LTC4040 is available in a low
profile (0.75mm) 24-Lead 4mm × 5mm QFN package.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 6522118, 6570372,
6700364, 8139329.
Typical Application
4.5V Backup Application with 4.22V PFI Threshold
(Charge Current Setting: 1A, Input Current Limit Setting: 2A)
4.5V INPUT
SUPPLY
2.2µF
12mΩ
4.5V
1500k
1A
SYSTEM
LOAD
100µF
154k
60.4k
VIN CLN
OVSNS
PFI
IGATE
VSYS
BSTFB
RSTFB
FAULT
PFO
RST
CHRG
CLPROG
LTC4040
CHGOFF BSTOFF F0 F1 F2
SW
BAT
NTC
PROG
VSYS
2k
324k
2.2µH
VIN
10µF
NTC +
LiFePO4
3.6V
4040 TA01a
Normal to Backup Mode Transition
NormaWlatoveBfoarcmku(pLiMFeoPdeO4TrAapnps.it)ion Waveform
5
VSYS
10
48
VBAT = 3.3V
3
VIN
ISYS = 1A
CSYS = 100µF
RPROG = 2k
6
24
1 IBAT 2
00
–1
–0.4
–2
0 0.4 0.8 1.2
TIME (ms)
4040 TA01b
For more information www.linear.com/LTC4040
4040fa
1
1 page  
LTC4040
Electrical Characteristics The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C. (Note 3) VIN = 5V, VBAT = 3.6V, RPROG = 2k, unless otherwise noted.
SYMBOL PARAMETER
Open-Drain Output (CHRG, RST, FAULT)
Pin Leakage Current
Pin Output Low Voltage
Overvoltage Protection
VOV(CUTOFF) Overvoltage Protection Threshold
VOVGT
IGATE Output Voltage Active
VOVGT(LOAD) IGATE Voltage Under Load
IOVSNSQ OVSNS Quiescent Current
OVSNS Quiescent Current at Shutdown
IGATE Time to Reach Regulation
CONDITIONS
V = 5V
I = 5mA
Rising Threshold, ROVSNS = 6.2k
Input Voltage < VOV(CUTOFF)
5V Through 6.2k Into OVSNS, IIGATE = 1µA
VOVSNS = 5V
BSTOFF = H, CHGOFF = H
CIGATE = 2.2nF
MIN TYP MAX UNITS
1
65
µA
mV
6.1 6.4 6.7
1.88 •
VOVSNS
12
8 8.6
40
25
3.5
V
V
V
µA
µA
ms
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: 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 impair device reliability.
Note 3: The LTC4040E is tested under pulsed load conditions such that
TJ ≈ TA. The LTC4040E is guaranteed to meet performance 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 control. The
LTC4040I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The junction temperature (TJ in °C) is calculated from
the ambient temperature (TA, in °C) and power dissipation (PD, in watts)
according to the formula:
TJ = TA + (PD • θJA)
where the package thermal impedance θJA = 43°C/W.
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.
For more information www.linear.com/LTC4040
4040fa
5
5 Page 
LTC4040
Pin Functions
OVSNS (Pin 16): Overvoltage Protection Sense Input. If
the overvoltage feature is used, the OVSNS pin should be
connected through a 6.2k resistor to an input power con-
nector and the drain of an N-channel MOS pass transistor.
If not, this pin should be shorted to VIN. When voltage is
detected on OVSNS, it draws a small amount of current to
power a charge pump which then provides gate drive to
IGATE to energize the external transistor. When the voltage
on this pin exceeds typically 6V, IGATE is pulled to GND
to disable the pass transistor and protect the LTC4040
from high voltage.
NTC (Pin 17): Input to the Thermistor Monitoring Circuits.
The NTC pin connects to a battery’s thermistor to deter-
mine if the battery is too hot or too cold to charge. If the
battery’s temperature is out of range, charging is paused
until it re-enters the valid range. A low drift bias resistor
is required from VIN to NTC and a thermistor is required
from NTC to ground. If the NTC function is not desired,
the NTC pin should be grounded.
BSTFB (Pin 18): Feedback Input for the Backup Boost
Regulator. During steady-state backup operation, voltage
on this pin servos to 0.8V.
PFI (Pin 19): Power-Fail Input. High impedance input to
an accurate comparator (power-fail) with a 1.19V falling
threshold and 30mV hysteresis. PFI controls the state of
the PFO output pin and sets the input voltage threshold
below which the boost backup is initiated. This threshold
voltage also represents the minimum voltage above which
the step-down battery charger is enabled and the part al-
lows power to flow from the input to the output through
the external pass transistors.
PFO (Pin 20): Open-Drain Power-Fail Status Output. This
pin is pulled to ground by an internal N-channel MOSFET
when the PFI input is below the falling threshold of the
power-fail comparator. Once the PFI input rises above
the rising threshold, this pin becomes high impedance.
SW (Pins 21, 22): Power Transmission Pin for the Buck
Switching Charger and the Boost Switching Backup
Converter. A 1µH to 2.2µH inductor should be connected
from SW to BAT.
BAT (Pin 23): Single Cell Li-Ion or LiFePO4 Battery Pin.
Depending on the availability of input power, the battery
will either deliver power to VSYS via the boost converter
or be charged from VSYS via the buck charger. BAT should
be bypassed with a low ESR ceramic capacitor of at least
10µF to GND.
GND (Exposed Pad Pin 25): The exposed pad must be
soldered to the PCB to provide a low electrical and ther-
mal impedance connection to the printed circuit board’s
ground. A continuous ground plane on the second layer of
a multilayer printed circuit board is strongly recommended.
For more information www.linear.com/LTC4040
4040fa
11
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet LTC4040.PDF ] | |
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