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LTM8061EV-8.4#PBF

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LTM8061
10
8061fa
For more information www.linear.com/LTM8601
applicaTions inForMaTion
Overview
The LTM8061 is a complete monolithic, mid-power, Li-Ion
battery charger, addressing high input voltage applications
with solutions that use a minimum of external components.
The product is available in four variants: 4.1V, 4.2V, 8.2V
and 8.4V fixed float voltages, each using 1MHz constant-
frequency, average current mode step-down architecture. A
2A power Schottky diode is integrated within the µModule
for reverse input voltage protection. A wide input range
allows the operation to full charge from 6V to 32V for
the LTM8061-4.1/LTM8061-4.2 and 11V to 32V for the
LTM8061-8.2/LTM8061-8.4 versions. A precision thresh
-
old RUN pin allows incorporation of UVLO functionality
using a simple resistor divider. The charger can also be
put into a low current shutdown mode, in which the input
supply bias is reduced to only 15μA.
The LTM8061 incorporates several degrees of charge
current control freedom. The maximum charge current
is internally set to approximately 2A. A maximum charge
current programming pin (RNG/SS) allows the charge
current to be reduced from the default 2A level. The
LTM8061 also incorporates an input supply current limit
control feature (V
INC
/CLP) that servos the battery charge
current to
accommodate overall system load requirements.
The LTM8061 automatically enters a battery precondition
mode if the sensed battery voltage is very low. In this
mode, the charge current is reduced to 300mA. Once the
battery voltage climbs above the internally set precondition
threshold (2.9V for the LTM8061-4.1/LTM8061-4.2, 5.65V
for the LTM8061-8.2, and 5.8V for the LTM8061-8.4), the
µModule automatically increases the maximum charge
current to the full programmed value.
The LTM8061 can use a charge current based C/10 termina
-
tion scheme, which ends a charge cycle when the battery
charge current falls to one-tenth the programmed charge
current. The LTM8061 also contains an internal charge cycle
control timer, for timer-based termination. When using the
internal timer, the charge cycle can continue beyond the
C/10 level to top-off a battery. The charge cycle terminates
when the programmed time elapses, typically chosen to
be three hours. The CHRG status pin continues to signal
charging at a C/10 rate, regardless of which termination
scheme is used. When the timer-based scheme is used,
the device also supports bad battery detection, which
triggers a system fault if a battery stays in precondition
mode for more than one
-eighth of the total programmed
charge cycle time.
Once charging terminates and the LTM8061 is not actively
charging, the device automatically enters a low current
standby mode in which supply bias currents are reduced
to 85μA. If the battery voltage drops 2.5% from the full
charge float voltage, the LTM8061 engages an automatic
charge cycle restart. The device also automatically restarts
a new charge cycle after a bad-battery fault once the failed
battery is removed and replaced with another battery.
The LTM8061 contains a battery temperature monitoring
circuit. This feature, using a thermistor, monitors battery
temperature and will not allow charging to begin, or will
suspend charging, and signal a fault condition if the battery
temperature is outside a safe charging range. The LTM8061
contains two digital open-collector outputs, which provide
charger status and signal fault conditions. These binary
coded pins signal battery charging, standby or shutdown
modes, battery temperature faults and bad battery faults.
For reference, C/10 and TMR based charging cycles are
shown in Figures 1 and 2.
LTM8061
11
8061fa
For more information www.linear.com/LTM8601
8061 F01
BATTERY VOLTAGE
BATTERY CHARGE
CURRENT
RUN
CHRG
FAULT
MAXIMUM CHARGE CURRENT
PRECONDITION CURRENT
C/10
0 AMPS
FLOAT VOLTAGE
RECHARGE THRESHOLD
PRECONDITION THRESHOLD
1
0
1
0
0
1
applicaTions inForMaTion
8061 F02
BATTERY VOLTAGE
BATTERY CHARGE
CURRENT
RUN
CHRG
FAULT
MAXIMUM CHARGE CURRENT
PRECONDITION CURRENT
C/10 CURRENT
AUTOMATIC
RESTART
FLOAT VOLTAGE
RECHARGE THRESHOLD
PRECONDITION THRESHOLD
1
0
1
0
0
< t
EOC
/8
t
EOC
1
Figure 1. Typical C/10 Terminated Charge Cycle (TMR Grounded, Time Not to Scale)
Figure 2. Typical EOC (Timer-Based) Terminated Charge Cycle (Capacitor Connected to TMR, Time Not to Scale)
LTM8061
12
8061fa
For more information www.linear.com/LTM8601
applicaTions inForMaTion
V
IN
Input Supply
The LTM8061 is biased directly from the charger input
supply through the V
IN
pin. This pin carries large switched
currents, so a high quality, low ESR decoupling capacitor
is recommended to minimize voltage glitches on V
IN
. A
4.7µF capacitor is typically adequate for most charger
applications.
Reverse Protection Diode
The LTM8061 integrates a high voltage power Schottky
diode to provide input reverse voltage protection. The
anode of this diode is connected to V
INA
, and the cath-
ode is connected to V
INC/CLP
. There is a small amount of
capacitance at each end; please see the Block Diagram.
BIAS Pin Considerations
The BIAS pin is used to provide drive power for the internal
power switching stage and operate other internal circuitry.
For proper operation, it must be powered by at least 2.9V
and no more than the absolute maximum rating of 10V.
In most applications, connect BIAS to BAT.
When charging a 2-cell battery using a relatively high input
voltage, the LTM8061 power dissipation can be reduced
by connecting BIAS to a 3.3V source.
BAT Decoupling Capacitance
In many applications, the internal BAT capacitance of the
LTM8061 is sufficient for proper operation. There
are cases,
however, where it may be necessary to add capacitance or
otherwise modify the output impedance of the LTM8061.
Case 1: the µModule charger is physically located far from
the battery and the added line impedance may interfere with
the control loop. Case 2: the battery ESR is very small or
very large; the LTM8061 controller is designed for a wide
range, but some battery packs have an ESR outside of this
range. Case 3: there is no battery at all. As the charger is
designed to work with the ESR of the battery, the output
may oscillate if no battery is present.
V
IN
V
INC
/CLP
8061 F03
LTM8061
INPUT SUPPLY
SYSTEM LOAD
R
CLP
Figure 3. R
CLP
Sets the Input Supply Current Limit
The optimum ESR is about 100mΩ, but ESR values both
higher and lower will work. Table 1 shows a sample of
parts verified by Linear Technology:
Table 1. Recommended BAT Capacitors
PART NUMBER DESCRIPTION MANUFACTURER
16TQC22M 22µF, 16V, POSCAP Sanyo
35SVPD18M 18µF, 35V, OS-CON Sanyo
TPSD226M025R0100 22µF, 25V Tantalum AVX
T495D226K025AS 22µF, 25V, Tantalum Kemet
TPSC686M006R0150 68µF, 6V, Tantalum AVX
TPSB476M006R0250 47µF, 6V, Tantalum AVX
APXE100ARA680ME61G 68µF, 10V Aluminum Nippon Chemicon
APS-150ELL680MHB5S 68µF, 25V Aluminum Nippon Chemicon
If system constraints preclude the use of electrolytic ca-
pacitors, a series R-C network may be used. Use a ceramic
capacitor of at least 22µF and an equivalent resistance of
100mΩ.
CLP: Input Current Limit
The LTM8061 contains a PowerPath™ control feature to
support multiple load systems. The charger adjusts charge
current in response to a system load if input supply current
exceeds the programmed maximum value. Maximum input
supply current is set by connecting a sense resistor (R
CLP
)
as shown in Figure 3. The LTM8061 begins to limit the
charge current when the voltage across the sense resistor
is 50mV. The maximum input current is defined by:
R
CLP
= 0.05/(Max Input Current)
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LTM8061EV-8.4#PBF

Mfr. #:
Buy LTM8061EV-8.4#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Battery Management 32V, 2A Module Li-Ion/ Polymer Bat Ch
Lifecycle:
New from this manufacturer.
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