LTC4070_15 Datasheet, PDF (1/16 Pages) Linear Technology – Li-Ion/Polymer Shunt Battery Charger System

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}
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LTC4070
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. For
applications requiring pack protection, see LTC4071.
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
V_IN
R_IN
Q1:FDR8508
V_CC
ADJ
LBO
NTCBIAS
LTC4070
NTC
GND
10k
+
T
Li-Ion
NTHS0805N02N1002F
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
4070fc
1