DC1645A-D Linear Technology, DC1645A-D Datasheet - Page 15

• 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
Termination at the end of the timer cycle only occurs if the
charge cycle was successful. A successful charge cycle
occurs when the battery is charged to within 2.5% of the
full-charge float voltage. If a charge cycle is not success-
ful at EOC, the timer cycle resets and charging continues
for another full timer cycle. When V
the full-charge float voltage, whether by battery loading
or replacement of the battery, the charger automatically
resets and starts charging.
Preconditioning and Bad-Battery Fault
The LTM8061 has a precondition mode, in which charge
current is limited to 15% of the maximum charge current,
roughly 300mA. Precondition mode is engaged if the volt-
age on the BAT pin is below the precondition threshold,
or approximately 70% of the float voltage. Once the BAT
voltage rises above the precondition threshold, normal
full-current charging can commence. The LTM8061
incorporates 90mV hysteresis to avoid spurious mode
transitions.
Bad-battery detection is engaged when using timer termi-
nation. This fault detection feature is designed to identify
failed cells. A bad-battery fault is triggered when the volt-
age on BAT remains below the precondition threshold for
greater than one-eighth of a full timer cycle (one-eighth
EOC). A bad-battery fault is also triggered if a normally
charging battery re-enters precondition mode after one-
eighth EOC.
When a bad-battery fault is triggered, the charge cycle
is suspended, and the CHRG status pin becomes high
impedance. The FAULT pin is pulled low to signal that a
fault has been detected. The RNG/SS pin is also pulled
low during this fault to accommodate a graceful restart
in the event that a soft-start function is incorporated (see
the RNG/SS: Soft-Start section).
Cycling the charger’s power or shutdown function initiates
a new charge cycle, but the LTM8061 charger does not
require a manual reset. Once a bad-battery fault is detected,
a new timer charge cycle initiates if the BAT pin exceeds
the precondition threshold voltage. During a bad-battery
fault, a small current is sourced from the charger; removing
the failed battery allows the charger output voltage to rise
BAT
drops 2.5% from
above the preconditioning threshold voltage and initiate a
charge cycle reset. A new charge cycle is started by con-
necting another battery to the charger output.
Battery Temperature Fault: NTC
The LTM8061 can accommodate battery temperature
monitoring by using an NTC (negative temperature coef-
ficient) thermistor close to the battery pack. The tem-
perature monitoring function is enabled by connecting
a 10kΩ, β = 3380 NTC thermistor from the NTC pin to
ground. If the NTC function is not desired, leave the pin
unconnected. The NTC pin sources 50μA, and monitors
the voltage dropped across the 10kΩ thermistor. When the
voltage on this pin is above 1.36V (0°C) or below 0.29V
(40°C), the battery temperature is out of range, and the
LTM8061 triggers an NTC fault. The NTC fault condition
remains until the voltage on the NTC pin corresponds to
a temperature within the 0°C to 40°C range. Both hot and
cold thresholds incorporate 20% hysteresis, which equates
to about 5°C. If higher operational charging temperatures
are desired, the temperature range can be expanded by
adding series resistance to the 10k NTC resistor. Adding
a 909Ω resistor will increase the effective temperature
threshold to 45°C, for example.
During an NTC fault, charging is halted and both status
pins are pulled low. If timer termination is enabled, the
timer count is suspended and held until the fault condi-
tion is cleared. The RNG/SS pin is also pulled low during
this fault to accommodate a graceful restart in the event
that a soft-start function is being incorporated (see the
RNG/SS: Soft-Start section).
Thermal Foldback
The LTM8061 contains a thermal foldback protection feature
that reduces charge current as the internal temperature
approaches 125°C. In most cases, internal temperatures
servo such that any overtemperature conditions are relieved
with only slight reductions in maximum charge current.
In some cases, the thermal foldback protection feature
can reduce charge currents below the C/10 threshold. In
applications that use C/10 termination (TMR = 0V), the
LTM8061 will suspend charging and enter standby mode
until the overtemperature condition is relieved.
LTM8061
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8061f