LTC4097EDDB LINER [Linear Technology], LTC4097EDDB Datasheet - Page 11

• Manufacturer Part Number: LTC4097EDDB
• Description: USB/Wall Adapter Standalone Li-Ion/Polymer Battery Charger
• Manufacturer: LINER [Linear Technology]

OPERATION
The LTC4097 is designed to effi ciently manage charging
a single-cell lithium-ion battery from two separate power
sources: a wall adapter and USB power bus. Using the
constant-current/constant-voltage algorithm, the charger
can deliver up to 1.2A of charge current from the wall
adapter supply or up to 1A of charge current from the
USB supply with a fi nal fl oat voltage accuracy of ±0.6%.
The LTC4097 has two internal P-channel power MOSFETs,
thermal regulation and shut down circuitry. No blocking
diodes or external sense resistors are required.
Power Source Selection
The LTC4097 can charge a battery from either the wall
adapter input or the USB port input. The LTC4097 automati-
cally senses the presence of voltage at each input. If both
power sources are present, the LTC4097 defaults to the
wall adapter source provided suffi cient power is present
at the DCIN input. “Suffi cient power” is defi ned as:
The VNTC output pin indicates that suffi cient input voltage
is available. Table 1 describes the behavior of the power
source selection.
Table 1. Power Source Selection
V
V
V
V
DCIN
DCIN
DCIN
DCIN
• Supply voltage is greater than the UVLO threshold.
• Supply voltage is greater than the battery voltage by
30mV (100mV or 150mV rising, 30mV falling).
> 4.2V and
> BAT + 30mV
< 4.2V or
< BAT + 30mV
V
V
Charger powered from
wall adapter source;
USBIN current < 25µA
Charger powered from
USB source
USBIN
USBIN
> 4V and
> BAT + 30mV
V
V
Charger powered from
wall adapter source
No charging
USBIN
USBIN
< 4V or
< BAT + 30mV
Programming and Monitoring Charge Current
The charge current delivered to the battery from the wall
adapter supply is programmed using a single resistor from
the IDC pin to ground.
Similarly, the charge current from the USB supply is
programmed using a single resistor from the IUSB pin
to ground. Setting HPWR pin to its high state will select
100% of the programmed charge current, while setting
HPWR to its low state will select 20% of the programmed
charge current.
Charge current out of the BAT pin can be determined at
any time by monitoring the IDC or IUSB pin voltage and
applying the following equations:
I
I
I
I
R
R
( arg
( arg
I
BAT
BAT
CHRG USB
CHRG USB
BAT
ch
ch
IDC
IUSB
=
=
=
=
(
(
=
R
R
ing from USB
in
V
V
R
I
V
CHRG DC
IDC
IUSB
IDC
IUSB
1000
I
IUSB
IUSB
g g from USB
CHRG USB
)
)
1000
= =
=
•
(
1000
R
200
•
1000
•
R
(
V
IUS
1000
200
IUSB
)
V
,
V
B B
)
I
CHRG DC
V
, ( arg
,
(
(
,
ch
sup
sup
HPWR HIGH
HPWR LOW
(
HPWR HIGH
(
p
ply HPWR LOW
l l y HPWR HIGH
)
ing from wall adapter
,
,
=
=
=
=
1000
R
IDC
)
LTC4097
)
V
=
=
)
)
)
11
) )
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