lt3650-4.1 Linear Technology Corporation, lt3650-4.1 Datasheet - Page 13

• Manufacturer Part Number: lt3650-4.1
• Description: High Voltage 2 Amp Monolithic Li-ion Battery Charger
• Manufacturer: Linear Technology Corporation

Rectifi er Selection
The rectifi er diode in an LT3650 battery charger provides a
current path for the inductor current when the main power
switch is disabled. The rectifi er is selected based upon
forward voltage, reverse voltage, and maximum current.
A Schottky diode is required, as low forward voltage yields
the lowest power loss and highest effi ciency. The rectifi er
diode must be rated to withstand reverse voltages greater
than the maximum V
The minimum average diode current rating (I
calculated with maximum output current (I
operational V
(V
For example, a rectifi er diode for a 4.2V, 1.5A charger with
a 20V maximum input voltage would require:
APPLICATIONS INFORMATION
BAT(PRE)
I
I
I
DIODE MAX
DIODE MAX
DIODE MAX
INPUT SUPPLY
Figure 4. R
(
(
(
):
IN
)
)
)
, and output at the precondition threshold
>
>
>
CLP
1. . 3A
I
1 5 20 2 9
MAX
. • (
Sets the Input Supply Current Limit
IN
R
CLP
voltage.
•
20
(
V
IN MAX
−
V
(
IN MA
. )
SYSTEM LOAD
(
)
,
V
CLP
IN
or
−
X X
)
V
:
BAT PRE
LT3650
MAX
(
DIODE(MAX)
), maximum
365042 F04
)
)
( )
A
) is
PowerPath is a trademark of Linear Technology Corporation.
CLP: System Current Limit
The LT3650 contains a PowerPath
support multiple load systems. The charger adjusts output
current in response to a system load if overall input supply
current exceeds the programmed maximum value.
Maximum input supply current is set by choosing a sense
resistor (R
through that sense resistor creates a 50mV drop, or:
where I
limit, for example, would use a 33mΩ sense resistor.
The LT3650 integrates the CLP signal internally, so average
current limiting is performed in most cases without the
need for external fi lter elements.
R
CLP
MAX(IN)
=
1.5A
1.0A
0.5A
CLP
Figure 5. CLP Limit: Charger Current vs
System Load Current with 1.5A Limit
I
MAX IN
LT3650-4.1/LT3650-4.2
0 05
CURRENT (I
is the maximum input current. A 1.5A system
) such that the desired maximum current
LT3650 INPUT
.
( )
VIN
)
SYSTEM LOAD
CURRENT
TM
control feature to
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