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PDF LTC4070 Data sheet ( Hoja de datos )
| Número de pieza | LTC4070 | |
| Descripción | Li-Ion/Polymer Shunt Battery Charger System | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
n Low Operating Current (450nA)
n 1% Float Voltage Accuracy Over Full Temperature
and Shunt Current Range
n 50mA Maximum Internal Shunt Current
(500mA with External PFET)
n Pin Selectable Float Voltage Options:
4.0V, 4.1V, 4.2V
n Ultralow Power Pulsed NTC Float Conditioning for
Li-Ion/Polymer Protection
n Suitable for Intermittent, Continuous and Very Low
Power Charging Sources
n Low and High Battery Status Outputs
n Simple Low Voltage Load Disconnect Application
n Thermally Enhanced, Low Profile (0.75mm)
8-Lead (2mm × 3mm) DFN and MSOP Packages
APPLICATIONS
n Low Power Li-Ion/Polymer Battery Back-Up
n Solar Power Systems with Back-Up
n Memory Back-Up
n Embedded Automotive
n Thin Film Batteries
n Energy Scavenging/Harvesting
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners..
LTC4070www.DataSheet4U.com
Li-Ion/Polymer Shunt
Battery Charger System
DESCRIPTION
The LTC®4070 allows simple charging of Li-Ion/Polymer
batteries from very low current, intermittent or continuous
charging sources. The 450nA to 50mA operating cur-
rent makes charging possible from previously unusable
sources. With the addition of an external pass device,
shunt current may be boosted to 500mA. Stacked cell high
voltage battery packs are inherently balanced with shunt
charging. With its low operating current, the LTC4070 is
well suited to charge thin film batteries in energy harvesting
applications where charging sources may be intermittent
or very low power. The unique architecture of the LTC4070
allows for an extremely simple battery charger solution;
requiring just one external resistor.
The LTC4070 offers a pin selectable float voltage with 1%
accuracy across the full range of operating temperature
and shunt current. The integrated thermal battery quali-
fier extends battery lifetime and improves reliability by
automatically reducing the battery float voltage at NTC
thermistor temperatures above 40°C. The LTC4070 also
provides both low and high battery status outputs. With
the addition of an external PFET, the low-battery output
pin can implement a latch-off function that automatically
disconnects the system load from the battery to protect
the battery from deep discharge.
The device is offered in two thermally enhanced packages,
a compact low profile (0.75mm) 8-lead (2mm × 3mm)
DFN and an 8-lead MSOP package.
TYPICAL APPLICATION
Simple Shunt Charger with Load
Disconnect and NTC Conditioning
VIN
RIN Q1:FDR8508
VCC
ADJ
LBO
NTCBIAS
LTC4070
NTC
GND
10k
+
T Li-Ion
NTHS0805E3103LT
4070 TA01a
NTC Overtemperature Battery Float Voltage Qualifying
4.3
4.2 ADJ = VCC
4.1 ADJ = FLOAT
4.0 ADJ = GND
3.9
3.8
3.7
0
20 40 60 80 100
TEMPERATURE (°C)
4070 TA01b
4070f
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LTC4070www.DataSheet4U.com
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
VOH LBO/HBO vs ISOURCE
2.5
2.0
LBO
VCC = 3.1V
1.5
1.0
HBO
VCC = VF – 25m
VOL LBO/HBO vs ISINK
2.5
VCC = 3.7V
2.0
1.5
1.0
0.5 0.5
0
0 0.5 1.0 1.5 2.0 2.5 3.0
ISOURCE (mA)
4070 G10
0
0 2 4 6 8 10
ISINK (mA)
4070 G11
Power Spectral Density
35
CC = 10μF, ICC = 1mA, 1Hz Res
30
Bandwidth, Noise = 1.0452mVRMS
from 10Hz to 100kHz
25
20
15
10
5
0
0 1 10 100 1000 10000 100000
FREQUENCY (Hz)
4070 G12
Hot Plug Transient, CC = 330μF,
RIN = 81Ω
CH1 = VIN
(2V/DIV)
CH4 = IIN
(10mA/DIV)
CH2 = VCC
(2V/DIV)
CH3 = VHBO
(2V/DIV)
4ms/DIV
4070 G13
Step Response with 800mAHr
Battery, RIN = 81Ω
CH4 = IIN (10mA/DIV)
CH1 = VIN (2V/DIV)
CH2 = VCC (2V/DIV)
CH3 = VHBO (2V/DIV)
400ns/DIV
4070 G14
4070f
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LTC4070www.DataSheet4U.com
APPLICATIONS INFORMATION
points are found by looking up the curve 1 thermistor R/T
values plus RFIX that correspond to the ratios for NTCTH1
= 36.5%, NTCTH2 = 29.0%, NTCTH3 = 22.8%, and NTCTH4
= 17.8%. Selecting RFIX = 3.92k results in trip points of
39.9°C, 49.4°C, 59.2°C and 69.6°C.
Another technique may be used without adding an ad-
ditional component. Instead decrease RNOM to adjust the
NTCTH thresholds for a given R/T thermistor profile. For
example, if RNOM = 88.7k (with the same 100k curve 1
thermistor) then the temperature trip points are 41.0°C,
49.8°C, 58.5°C, and 67.3°C.
When using the NTC features of the LTC4070 it is important
to keep in mind that the maximum shunt current increases
as the float voltage, VFLOAT_EFF drops with NTC conditioning.
Reviewing the Typical Application with a 12V wall adapter
in Figure 1; the input resistor, RIN, should be increased
to 165Ω such that the maximum shunt current does not
exceed 50mA at the lowest possible float voltage due to
NTC conditioning, VFLOAT_MIN = 3.8V.
Thermal Considerations
At maximum shunt current, the LTC4070 may dissipate up
to 205mW. The thermal dissipation of the package should
be taken into account when operating at maximum shunt
current so as not to exceed the absolute maximum junc-
tion temperature of the device. With θJA of 40°C/W, in the
MSOP package, at maximum shunt current of 50mA the
junction temperature rise is about 8°C above ambient.
With ΘJA of 76°C/W in the DFN package, at maximum
shunt current of 50mA the junction temperature rise is
about 16°C above ambient.
Operation with an External PFET To Boost Shunt
Current
Table 2 lists recommended devices to increase the
maximum shunt current. Due to the requirement for low
capacitance on the DRV pin node, it is recommended that
only low gate charge and high threshold PFET devices be
used. Also it is recommended that careful PCB layout be
used to keep leakage at the DRV pin to a minimum as the
IDRV(SINK) current is typically 3μA.
Refer to device manufacturers data sheets for maximum
continuous power dissipation and thermal resistance when
selecting an external PFET for a particular application.
Table 2. Recommended External Shunt PFETS
DEVICE
FDN352AP
VENDOR
Fairchild
QGS
0.50nC
VTH(MIN)
–0.8V
Si3467DV
Vishay
1.7nC
–1.0V
Si3469DV
Vishay
3.8nC
–1.0V
DMP2130LDM Diodes Inc.
2.0nC
–0.6V
DMP3015LSS Diodes Inc.
7.2nC
–1.0V
RDS(ON)
0.33
0.073
0.041
0.094
0.014
4070f
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11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4070.PDF ] | |
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