LTC4012_15 Datasheet, PDF (8/28 Pages) Linear Technology – High Efficiency, Multi-Chemistry Battery Charger with PowerPath Control

LTC4012/
LTC4012-1/LTC4012-2
Pin Functions
CLN (Pin 1): Adapter Input Current Limit Negative Input.
The LTC4012 senses voltage on this pin to determine if
less charge current should be sourced to limit total input
current. The threshold is set 100mV below the CLP pin. An
external filter should be used to remove switching noise.
This input should be tied to CLP if not used. Operating
voltage range is (CLP – 110mV) to CLP.
CLP (Pin 2): Adapter Input Current Limit Positive Input.
The LTC4012 also draws power from this pin, including
a small amount for some shutdown functions. Operating
voltage range is GND to 28V.
INFET (Pin 3): PowerPath Control Output. This output
drives the gate of a PMOS pass transistor connected
between the DC input (DCIN) and the raw system supply
rail (CLP) to maintain a forward voltage of 25mV when a
DC input source is present. INFET is internally clamped
about 6V below CLP. Maximum operating voltage is CLP,
which is used to turn off the input PMOS transistor when
the DC input is removed.
DCIN (Pin 4): DC Sense Input. One of two voltage sense
inputs to the internal PowerPath controller (the other input
to the controller is CLP). This input is usually supplied
from an input DC power source. Operating voltage ranges
from GND to 28.2V.
ACP (Pin 5): Active-Low AC Adapter Present Indicator
Output. This open-drain output pulls to GND when adequate
AC adapter (DCIN) voltage is present. This output should
be left floating if not used.
SHDN (Pin 6): Active-low Shutdown Input. Driving SHDN
below 300mV unconditionally forces the LTC4012 into the
shutdown state. This input has a 40kΩ internal pulldown
to GND. Operating voltage range is GND to INTV_DD.
CHRG (Pin 7): Active-Low Charge Indicator Output. This
open-drain output provides three levels of information
about charge status using a strong pull-down, 25µA weak
pull-down or high impedance. Refer to the Operation and
Applications Information sections for further details. This
output should be left floating if not used.
ICL (Pin 8): Active-Low Input Current Limit Indicator Out-
put. This open-drain output pulls to GND when the charge
current is reduced because of AC adapter input current
limiting. This output should be left floating if not used.
V_FB (Pin 9, LTC4012): Battery Voltage Feedback Input. An
external resistor divider between FBDIV and GND with the
center tap connected to V_FB programs the charger output
voltage. In constant voltage mode, this pin is nominally
at 1.2085V. Refer to the Applications Information section
for complete details on programming battery voltage.
Operating voltage range is GND to 1.25V.
FVS0 (Pin 9, LTC4012-1/LTC4012-2): Battery Voltage
Select Input (LSB). This pin is one of two pins used on the
LTC4012-1 or LTC4012-2 to select one of four preset battery
voltages. Selection is done by connecting to either GND or
INTV_DD. Operating voltage range is GND to INTV_DD.
FBDIV (Pin 10, LTC4012): Battery Voltage Feedback
Resistor Divider Source. The LTC4012 connects this pin
to BAT when charging is in progress. FBDIV is an open-
drain PFET output to BAT with an operating voltage range
of GND to BAT.
FVS1 (Pin 10, LTC4012-1/LTC4012-2): Battery Voltage
Select Input (MSB). This pin is one of two pins used on
the LTC4012-1 or LTC4012-2 to select one of four preset
battery voltages. Selection is done by connecting to
either GND or INTV_DD. Operating voltage range is GND
to INTV_DD.
BAT (Pin 11): Battery Pack Connection. The LTC4012 uses
the voltage on this pin to control PWM operation when
charging. Operating voltage range is GND to CLN.
ITH (Pin 12): PWM Control Voltage and Compensation
Node. The LTC4012 develops a voltage on this pin to
control cycle-by-cycle peak inductor current. An external
R-C network connected to ITH provides PWM loop com-
pensation. Refer to the Applications Information section
for further details on establishing loop stability. Operating
voltage range is GND to INTV_DD.
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