LT3650EDD-8.4#PBF Linear Technology, LT3650EDD-8.4#PBF Datasheet - Page 9

• Manufacturer Part Number: LT3650EDD-8.4#PBF
• Description: IC CHARGER LI-ION 2A 12-DFN
• Manufacturer: Linear Technology
• Type: Battery Chargerr

Specifications of LT3650EDD-8.4#PBF

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 9 V ~ 32 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 12-WFDFN Exposed Pad
• Output Voltage: 8.4V
• Operating Temp Range: -40C to 85C
• Mounting: Surface Mount
• Pin Count: 12
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

OPERATION
OVERVIEW
LT3650 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 IC uses a 1MHz constant-frequency, average current
mode step-down architecture.
The LT3650 incorporates a 2A switch that is driven by a
bootstrapped supply to maximize effi ciency during charging
cycles. A wide input range allows the operation to full-
charge from 9V to 32V. A precision threshold shutdown
pin allows incorporation of UVLO functionality using a
simple resistor divider. The IC can also be put into a low
current shutdown mode, in which the input supply bias
is reduced to only 15μA.
The LT3650 incorporates several degrees of charge current
control freedom. The overall maximum charge current
is set using an external inductor current sense resistor.
A maximum charge current programming pin allows
dynamic manipulation of the battery charge current. The
LT3650 also incorporates a system input supply current
limit control feature that servos the battery charge current
to accommodate overall system load requirements.
The LT3650 automatically enters a battery precondition
mode if the sensed battery voltage is very low. In this
mode, the charge current is reduced to 15% of the
programmed maximum, as set by the inductor sense
resistor, R
above the internally set precondition threshold, the IC
automatically increases the maximum charge current to
the full programmed value.
The LT3650 can use a charge current based C/10 ter-
mination scheme, which ends a charge cycle when the
battery charge current falls to one-tenth the programmed
maximum charge current. The LT3650 also contains an
internal charge cycle control timer, for timer-based termina-
tion. When using the internal timer, the IC combines C/10
detection with a programmable time constraint, during
which the charging cycle can continue beyond the C/10
level to “top-off” a battery. The charge cycle terminates
when a specifi c time elapses, typically three hours. When
SENSE
. Once the battery voltage climbs
the timer-based scheme is used, the IC 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 is terminated and the LT3650 is not
actively charging, the IC 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 fl oat voltage, the LT3650 engages an automatic
charge cycle restart. The IC also automatically restarts a
new charge cycle after a bad-battery fault once the failed
battery is removed and replaced with another battery.
The LT3650 contains provisions for a battery temperature
monitoring circuit. This feature monitors battery tempera-
ture by using a thermistor during the charging cycle, sus-
pends charging, and signals a fault condition if the battery
temperature moves outside a safe charging range.
The LT3650 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.
General Operation (See Block Diagram)
The LT3650 uses average current mode control architec-
ture, such that the IC servos directly to average charge
current. The LT3650 senses charger output voltage via the
BAT pin. The difference between the voltage on this pin
and an internal fl oat voltage reference is integrated by the
voltage error amplifi er (V-EA). This amplifi er generates an
error voltage on its output (I
average current sensed across the inductor current sense
resistor, R
and BAT pins. The I
factor of 10, and imposed on the input of the current er-
ror amplifi er (C-EA). The difference between this imposed
voltage and the current sense resistor voltage is integrated,
with the resulting voltage (V
compared against an internally generated ramp. The output
of this comparison controls the charger’s switch.
SENSE
LT3650-8.2/LT3650-8.4
, which is connected between the SENSE
TH
voltage is then divided down by a
TH
C
) used as a threshold that is
), which corresponds to the
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