LTM8061 Datasheet, PDF (17/20 Pages) Linear Technology – 32V, 2A μModule Li-Ion/ Polymer Battery Charger

LTM8061
APPLICATIONS INFORMATION
of the LTM8061 can ring to more than twice the nominal
input voltage, possibly exceeding the LTM8061’s rating
and damaging the part. If the input supply is poorly con-
trolled or the user will be plugging the LTM8061 into an
energized supply, the input network should be designed
to prevent this overshoot. This can be accomplished by
installing a small resistor in series to V_IN, but the most
popular method of controlling input voltage overshoot is
to add an electrolytic bulk capacitor to the V_IN net. This
capacitor’s relatively high equivalent series resistance
damps the circuit and eliminates the voltage overshoot.
The extra capacitor improves low frequency ripple filter-
ing and can slightly improve the efficiency of the circuit,
though it is physically large.
Thermal Considerations
The temperature rise curves given in the Typical Perfor-
mance Characteristics section gives the thermal perfor-
mance of the LTM8061. These curves were generated by the
LTM8061 mounted to a 58cm² 4-layer FR4 printed circuit
board. Boards of other sizes and layer count can exhibit
different thermal behavior, so it is incumbent upon the user
to verify proper operation over the intended system’s line,
load and environmental operating conditions.
The junction to air and junction to board thermal resis-
tances given in the Pin Configuration diagram may also be
used to estimate the LTM8061 internal temperature. These
thermal coefficients are determined for maximum output
power per JESD 51-9, “JEDEC Standard, Test Boards for
Area Array Surface Mount Package Thermal Measure-
ments” through analysis and physical correlation. Bear in
mind that the actual thermal resistance of the LTM8061
to the printed circuit board depends upon the design of
the circuit board.
The internal temperature of the LTM8061 must be lower
than the maximum rating of 125°C, so care should be
taken in the layout of the circuit to ensure good heat
sinking of the LTM8061. The bulk of the heat flow out of
the LTM8061 is through the bottom of the module and
the LGA pads into the printed circuit board. Consequently
a poor printed circuit board design can cause excessive
heating, resulting in impaired performance or reliability.
Please refer to the PCB Layout section for printed circuit
board design suggestions.
The LTM8061 is equipped with a thermal foldback that
reduces the charge current as the internal temperature
approaches 125°C. This does not mean that it is impos-
sible to exceed the 125°C maximum internal temperature
rating. The ambient operating condition and other factors
may result in high internal temperatures.
Finally, be aware that at high ambient temperatures the
internal Schottky diode will have significant leakage current
increasing the quiescent current of the LTM8061.
TYPICAL APPLICATIONS
Two Cell 1A Li-Ion Battery Charger with C/10
Termination and Reverse Input Protection
V_IN
11.5V TO 32V
4.7μF
LTM8061-8.4
V_INA
V_INC/CLP
V_IN
RUN
RNG/SS
TMR
BAT
BIAS
CHRG
FAULT
NTC
10k
(1A CHARGE
CURRENT)
GND
8061 TA02
+ ^TWO
CELL
8.4V
BATTERY
Single Cell 2A Li-Ion Battery Charger with 3 Hour
Timer Termination and Reverse Input Protection
V_IN
6V TO 32V
4.7μF
0.68μF
LTM8061-4.2
V_INA
V_INC/CLP
V_IN
RUN
RNG/SS
TMR
BAT
BIAS
CHRG
FAULT
NTC
GND
8061 TA03
+
SINGLE
CELL
4.2V
BATTERY
8061f
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