DC1645A-D Linear Technology, DC1645A-D Datasheet - Page 10

• Manufacturer Part Number: DC1645A-D
• Description: BOARD EVAL LTM8061-8.4
• Manufacturer: Linear Technology
• Series: LTM®, uModule®r

Specifications of DC1645A-D

• Main Purpose: Power Management, Battery Charger
• Embedded: No
• Utilized Ic / Part: LTM8061
• Primary Attributes: 2 Cell- Li-Ion, 8.2V 2A Output
• Secondary Attributes: LED Status Indicators
• Lead Free Status / RoHS Status: Not applicable / Not applicable

APPLICATIONS INFORMATION
LTM8061
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 threshold
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 cur-
rent to be reduced from the default 2A level. The LTM8061
also incorporates an input supply current limit control
feature (V
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.
10
INC
/CLP) that servos the battery charge current
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.
8061f