LTC4075 LINER [Linear Technology], LTC4075 Datasheet - Page 7

• Manufacturer Part Number: LTC4075
• Description: Dual Input USB/AC Adapter Standalone Li-Ion Battery Chargers
• Manufacturer: LINER [Linear Technology]

PI FU CTIO S
USBIN (Pin 1): USB Input Supply Pin. Provides power to
the battery charger. The maximum supply current is 650mA.
This pin should be bypassed with a 1µF capacitor.
IUSB (Pin 2): Charge Current Program for USB Power.
The charge current is set by connecting a resistor, R
to ground. When charging in constant-current mode, this
pin servos to 1V. The voltage on this pin can be used to
measure the battery current delivered from the USB input
using the following formula:
ITERM (Pin 3): Termination Current Threshold Program.
The termination current threshold, I
connecting a resistor, R
by the following formula:
When the battery current, I
threshold, charging stops and the ⎯ C ⎯ H ⎯ R ⎯ G output becomes
high impedance.
This pin is internally clamped to approximately 1.5V. Driving
this pin to voltages beyond the clamp voltage can draw
large currents and should be avoided.
⎯ P ⎯ W ⎯ R (Pin 4): Open-Drain Power Supply Status Output.
When the DCIN or USBIN pin voltage is suffi cient to begin
charging (i.e. when the supply is greater than the under-
voltage lockout threshold and at least 180mV above the
battery terminal), the ⎯ P ⎯ W ⎯ R pin is pulled low by an internal
N-channel MOSFET. Otherwise ⎯ P ⎯ W ⎯ R is high impedance.
This output is capable of sinking up to 10mA, making it
suitable for driving an LED.
⎯ C ⎯ H ⎯ R ⎯ G (Pin 5): Open-Drain Charge Status Output. When
the LTC4075 is charging, the ⎯ C ⎯ H ⎯ R ⎯ G pin is pulled low by
an internal N-channel MOSFET. When the charge cycle is
completed, ⎯ C ⎯ H ⎯ R ⎯ G becomes high impedance. This output
U
I
I
BAT
TERMINATE
=
R
U
V
IUSB
IUSB
=
•1000
R
100
ITERM
U
V
ITERM
BAT
, to ground. I
, falls below the termination
TERMINATE
TERMINATE
, is set by
is set
IUSB
,
is capable of sinking up to 10mA, making it suitable for
driving an LED.
ENABLE (Pin 6): Enable Input. When the LTC4075 is
charging from the DCIN source, a logic low on this pin
enables the charger. When the LTC4075 is charging from
the USBIN source, a logic high on this pin enables the
charger. If this input is left fl oating, an internal 2MΩ
pulldown resistor defaults the LTC4075 to charge when
a wall adapter is applied and to shut down if only the USB
source is applied.
USBPWR (Pin 7): Open-Drain USB Power Status Output.
When the voltage on the USBIN pin is suffi cient to begin
charging and there is insuffi cient power at DCIN, the USB-
PWR pin is high impedance. In all other cases, this pin is
pulled low by an internal N-channel MOSFET, provided that
there is power present at the DCIN, USBIN, or BAT inputs.
This output is capable of sinking up to 1mA, making it
suitable for driving high impedance logic inputs.
IDC (Pin 8): Charge Current Program for Wall Adapter
Power. The charge current is set by connecting a resis-
tor, R
mode, this pin servos to 1V. The voltage on this pin can
be used to measure the battery current delivered from the
DC input using the following formula:
BAT (Pin 9): Charger Output and Regulator Input. This pin
provides charge current to the battery and regulates the
fi nal fl oat voltage to 4.2V.
DCIN (Pin 10): Wall Adapter Input Supply Pin. Provides
power to the battery charger. The maximum supply
current is 950mA. This should be bypassed with a 1μF
capacitor.
Exposed Pad (Pin 11): GND. The exposed backside of the
package is ground and must be soldered to PC board ground
for electrical connection and maximum heat transfer.
I
BAT
IDC
=
, to ground. When charging in constant-current
R
V
IDC
IDC
•1000
LTC4075/LTC4075X
4075Xf
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